%0 Journal Article %J Solar Energy Materials and Solar Cells %D 2012 %T Fenestration of Today and Tomorrow: A State-of-the-Art Review and Future Research Opportunities %A Bjørn Petter Jelle %A Andrew Hynd %A Arlid Gustavsen %A Dariush K. Arasteh %A Howdy Goudey %A Robert Hart %K Fenestration %K Low-e %K Multilayer glazing %K Smart window %K Solar cell glazing %K Vacuum glazing %X

Fenestration of today is continuously being developed into the fenestration of tomorrow, hence offering a steadily increase of daylight and solar energy utilization and control, and at the same time providing a necessary climate screen with a satisfactory thermal comfort. Within this work a state of the art market review of the best performing fenestration products has been carried out, along with an overview of possible future research opportunities for the fenestration industry. The focus of the market review was low thermal transmittance (U-value). The lowest centre of glass Ug-values found was 0.28 W/(m2K) and 0.30 W/(m2K), which was from a suspended coating glazing product and an aerogel glazing product, respectively. However, the majority of high performance products found were triple glazed. The lowest frame U-value was 0.61 W/(m2K). Vacuum glazing, smart windows, solar cell glazing, window frames, self cleaning glazing, low-emissivity coatings and spacers were also reviewed, thus also representing possibilities for controlling and harvesting the solar radiation energy. Currently, vacuum glazing, new spacer materials and solutions, electrochromic windows and aerogel glazing seem to have the largest potential for improving the thermal performance and daylight and solar properties in fenestration products. Aerogel glazing has the lowest potential U-values, ~ 0.1 W/(m2K), but requires further work to improve the visible transmittance. Electrochromic vaccum glazing and evacuated aerogel glazing are two vacuum related solutions which have a large potential. There may also be opportunities for completely new material innovations which could revolutionize the fenestration industry.

%B Solar Energy Materials and Solar Cells %V 96 %P 1-28 %8 01/2012 %G eng %1

Windows and Daylighting Group

%2 LBNL-5304E %& 1 %R 10.1016/j.solmat.2011.08.010 %0 Journal Article %J Energy and Buildings %D 2011 %T Key Elements of and Materials Performance Targets for Highly Insulating Window Frames %A Arlid Gustavsen %A Steinar Grynning %A Dariush K. Arasteh %A Bjørn Petter Jelle %A Howdy Goudey %K Fenestration %K heat transfer modeling %K thermal performance %K thermal transmittance %K u-factor %K window frames %X

The thermal performance of windows is important for energy efficient buildings. Windows typically account for about 30–50 percent of the transmission losses though the building envelope, even if their area fraction of the envelope is far less. The reason for this can be found by comparing the thermal transmittance (U-factor) of windows to the U-factor of their opaque counterparts (wall, roof and floor constructions). In well insulated buildings the U-factor of walls, roofs and floors can be between 0.1 and 0.2 W/(m2 K). The best windows have U-factors of about 0.7–1.0. It is therefore obvious that the U-factor of windows needs to be reduced, even though looking at the whole energy balance for windows (i.e., solar gains minus transmission losses) makes the picture more complex.

In high performance windows the frame design and material use are of utmost importance, as the frame performance is usually the limiting factor for reducing the total window U-factor further. This paper describes simulation studies analyzing the effects on frame and edge-of-glass U-factors of different surface emissivities as well as frame material and spacer conductivities. The goal of this work is to define material research targets for window frame components that will result in better frame thermal performance than is exhibited by the best products available on the market today.

%B Energy and Buildings %V 43 %P 2583-2594 %8 10/2011 %G eng %N 10 %1

Windows and Daylighting Group

%2 LBNL-5099E %& 2583 %R 10.1016/j.enbuild.2011.05.010 %0 Conference Paper %B Thermal Performance of the Exterior Envelopes of Whole Buildings XI International Conference, December 5-9, 2010 %D 2010 %T Experimental and Numerical Examination of the Thermal Transmittance of High Performance Window Frames %A Arlid Gustavsen %A Goce Talev %A Dariush K. Arasteh %A Howdy Goudey %A Christian Kohler %A Sivert Uvsløkk %A Bjørn Petter Jelle %K experimental %K Fenestration %K frame cavity %K heat transfer modeling %K hot box %K international standards %K thermal transmittance %K U-value %K window frames %X

While window frames typically represent 20-30% of the overall window area, their impact on the total window heat transfer rates may be much larger. This effect is even greater in low-conductance (highly insulating) windows which incorporate very low conductance glazings. Developing low-conductance window frames requires accurate simulation tools for product research and development.

The Passivhaus Institute in Germany states that windows (glazing and frames, combined) should have U-values not exceeding 0.80 W/(m2 K). This has created a niche market for highly insulating frames, with frame U-values typically around 0.7-1.0 W/(m2 K). The U-values reported are often based on numerical simulations according to international simulation standards. It is prudent to check the accuracy of these calculation standards, especially for high performance products before more manufacturers begin to use them to improve other product offerings.

In this paper the thermal transmittance of five highly insulating window frames (three wooden frames, one aluminum frame and one PVC frame), found from numerical simulations and experiments, are compared. Hot box calorimeter results are compared with numerical simulations according to ISO 10077-2 and ISO 15099. In addition CFD simulations have been carried out, in order to use the most accurate tool available to investigate the convection and radiation effects inside the frame cavities.

Our results show that available tools commonly used to evaluate window performance, based on ISO standards, give good overall agreement, but specific areas need improvement.

%B Thermal Performance of the Exterior Envelopes of Whole Buildings XI International Conference, December 5-9, 2010 %C Clearwater Beach, FL %8 09/2010 %G eng %1

Windows and Daylighting Group

%2 LBNL-3886E %0 Report %D 2009 %T Modeling Windows in Energy Plus with Simple Performance Indices %A Dariush K. Arasteh %A Christian Kohler %A Brent T. Griffith %X

The paper describes the development of a model specification for performance monitoring systems for commercial buildings. The specification focuses on four key aspects of performance monitoring:

The aim is to assist building owners in specifying the extensions to their control systems that are required to provide building operators with the information needed to operate their buildings more efficiently and to provide automated diagnostic tools with the information required to detect and diagnose faults and problems that degrade energy performance.

The paper reviews the potential benefits of performance monitoring, describes the specification guide and discusses briefly the ways in which it could be implemented. A prototype advanced visualization tool is also described, along with its application to performance monitoring. The paper concludes with a description of the ways in which the specification and the visualization tool are being disseminated and deployed.

%8 10/2009 %G eng %L LBNL-2804E %1

Windows and Daylighting Group

%2 LBNL-2804E %0 Journal Article %J Journal of Building Physics %D 2008 %T Developing Low-Conductance Window Frames: Capabilities and Limitations of Current Window Heat Transfer Design Tools %A Arlid Gustavsen %A Dariush K. Arasteh %A Bjørn Petter Jelle %A Dragan C. Curcija %A Christian Kohler %X

While window frames typically represent 20-30% of the overall window area, their impact on the total window heat transfer rates may be much larger. This effect is even greater in low-conductance (highly insulating) windows which incorporate very low conductance glazings. Developing low-conductance window frames requires accurate simulation tools for product research and development. Based on a literature review and an evaluation of current methods of modeling heat transfer through window frames, we conclude that current procedures specified in ISO standards are not sufficiently adequate for accurately evaluating heat transfer through the low-conductance frames.

We conclude that the near-term priorities for improving the modeling of heat transfer through low-conductance frames are:

  1. Add 2-D view-factor radiation to standard modeling and examine the current practice of averaging surface emissivity based on area weighting and the process of making an equivalent rectangular frame cavity.
  2. Assess 3-D radiation effects in frame cavities and develop recommendation for inclusion into the design fenestration tools.
  3. Assess existing correlations for convection in vertical cavities using CFD.
  4. Study 2-D and 3-D natural convection heat transfer in frame cavities for cavities that are proven to be deficient from item 3 above. Recommend improved correlations or full CFD modeling into ISO standards and design fenestration tools, if appropriate.
  5. Study 3 D hardware short-circuits and propose methods to ensure that these effects are incorporated into ratings.
  6. Study the heat transfer effects of ventilated frame cavities and propose updated correlations.
%B Journal of Building Physics %V 32 %P 131-153 %G eng %L LBNL-1022E %1

Windows and Daylighting Group

%2 LBNL-1022E %0 Conference Paper %B 2008 Annual ASHRAE Meeting %D 2008 %T Highly Insulating Glazing Systems using Non-Structural Center Glazing Layers %A Dariush K. Arasteh %A Howdy Goudey %A Christian Kohler %X

Three layer insulating glass units with two low-e coatings and an effective gas fill are known to be highly insulating, with center-of-glass U-factors as low as 0.57 W/m2-K (0.10 Btu/h-ft2-°F). Such units have historically been built with center layers of glass or plastic which extend all the way through the spacer system.

This paper shows that triple glazing systems with non-structural center layers which do not create a hermetic seal at the edge have the potential to be as thermally efficient as standard designs, while potentially removing some of the production and product integration issues that have discouraged the use of triples.

%B 2008 Annual ASHRAE Meeting %C Salt Lake City, UT %8 06/2008 %G eng %2 LBNL-611E %0 Report %D 2008 %T WINDOW 6.2/THERM 6.2 Research Version User Manual %A Robin Mitchell %A Christian Kohler %A Joseph H. Klems %A Michael D. Rubin %A Dariush K. Arasteh %A Charlie Huizenga %A Tiefeng Yu %A Dragan C. Curcija %X

WINDOW 6 and THERM 6 Research Versions are software programs developed at Lawrence Berkeley National Laboratory (LBNL) for use by manufacturers, engineers, educators, students, architects, and others to determine the thermal and solar optical properties of glazing and window systems.

WINDOW 6 and THERM 6 are significant updates to LBNL's WINDOW 5 and THERM 5 computer program because of the added capability to model complex glazing systems, such as windows with shading systems, in particular venetian blinds. Besides a specific model for venetian blinds and diffusing layers, WINDOW 6 also includes the generic ability to model any complex layer if the Transmittance and Reflectance are known as a function of incoming and outgoing angles.

The algorithms used in these versions of the programs to determine the properties of windows with shading layers are relatively new and should be considered as informative but not definitive.

As such, for windows with shading layers, the results are intended for research purposes only. Pending further validation efforts, results for windows with sh ading layers should not be used for NFRC certified calculations of design decisions in real buildings.

All calculations for products without shading layers are identical to those from WINDOW 5.2.

WINDOW 6 Research Version includes all of the WINDOW 5 capabilities with the addition of shading algorithms from ISO15099 which are incorporated into the program, as well as an extension of those algorithms with the matrix calculation method.

THERM 6 Research Version includes all of the THERM 5 capabilities with the addition of being able to import and model WINDOW 6 glazing systems with shading devices. Those THERM 6 files with shading devices can them be imported into the WINDOW 6 Frame Library and whole windows with shading devices can then be modeled in WINDOW 6.

%I Lawrence Berkeley National Laboratory %C Berkeley %P 1-126 %8 01/2008 %G eng %1

Windows and Daylighting Group

%2 LBNL-813E %0 Report %D 2007 %T State-of-the-Art Highly Insulating Window Frames - Research and Market Review %A Arlid Gustavsen %A Bjørn Petter Jelle %A Dariush K. Arasteh %A Christian Kohler %K energy use %K Passivhaus %K thermal transmittance %K U-value %K window frame %K windows %X

This document reports the findings of a market and research review related to state-of-the-art highly insulating window frames. The market review focuses on window frames that satisfy the Passivhaus requirements (window U-value less or equal to 0.8 W/m2K), while other examples are also given in order to show the variety of materials and solutions that may be used for constructing window frames with a low thermal transmittance (U-value). The market search shows that several combinations of materials are used in order to obtain window frames with a low U-value. The most common insulating material seems to be Polyurethane (PUR), which is used together with most of the common structural materials such as wood, aluminum, and PVC.

The frame research review also shows examples of window frames developed in order to increase the energy efficiency of the frames and the glazings which the frames are to be used together with. The authors find that two main tracks are used in searching for better solutions. The first one is to minimize the heat losses through the frame itself. The result is that conductive materials are replaced by highly thermal insulating materials and air cavities. The other option is to reduce the window frame area to a minimum, which is done by focusing on the net energy gain by the entire window (frame, spacer and glazing). Literature shows that a window with a higher U-value may give a net energy gain to a building that is higher than a window with a smaller U-value. The net energy gain is calculated by subtracting the transmission losses through the window from the solar energy passing through the windows. The net energy gain depends on frame versus glazing area, solar factor, solar irradiance, calculation period and U-value.

The frame research review also discusses heat transfer modeling issues related to window frames. Thermal performance increasing measures, surface modeling, and frame cavity modeling are among the topics discussed. The review shows that the current knowledge gives the basis for improving the calculation procedures in the calculation standards. At the same time it is room for improvement within some areas, e.g. to fully understand the natural convection effects inside irregular vertical frame cavities (jambs) and ventilated frame cavities.

%B SINTEF Building and Infrastructure %I INTEF Building and Infrastructure %C Olso %@ 978-82-536-0970-6 %G eng %1

Windows and Daylighting Group

%2 LBNL-1133E %0 Conference Paper %B 2007 ASHRAE Winter Meeting %D 2007 %T Two-Dimensional Computational Fluid Dynamics and Conduction Simulations of Heat Transfer in Horizontal Window Frames with Internal Cavities %A Arlid Gustavsen %A Christian Kohler %A Arvid Dalehaug %A Dariush K. Arasteh %X

This paper assesses the accuracy of the simplified frame cavity conduction/convection and radiation models presented in ISO 15099 and used in software for rating and labeling window products. Temperatures and U-factors for typical horizontal window frames with internal cavities are compared; results from Computational Fluid Dynamics (CFD) simulations with detailed radiation modeling are used as a reference.

Four different frames were studied. Two were made of polyvinyl chloride (PVC) and two of aluminum. For each frame, six different simulations were performed, two with a CFD code and four with a building-component thermal-simulation tool using the Finite Element Method (FEM). This FEM tool addresses convection using correlations from ISO 15099; it addressed radiation with either correlations from ISO 15099 or with a detailed, view-factor-based radiation model. Calculations were performed using the CFD code with and without fluid flow in the window frame cavities; the calculations without fluid flow were performed to verify that the CFD code and the building-component thermal-simulation tool produced consistent results. With the FEM-code, the practice of subdividing small frame cavities was examined, in some cases not subdividing, in some cases subdividing cavities with interconnections smaller than five millimeters (mm) (ISO 15099) and in some cases subdividing cavities with interconnections smaller than seven mm (a breakpoint that has been suggested in other studies). For the various frames, the calculated U-factors were found to be quite comparable (the maximum difference between the reference CFD simulation and the other simulations was found to be 13.2 percent). A maximum difference of 8.5 percent was found between the CFD simulation and the FEM simulation using ISO 15099 procedures. The ISO 15099 correlation works best for frames with high U-factors. For more efficient frames, the relative differences among various simulations are larger.

Temperature was also compared, at selected locations on the frames. Small differences was found in the results from model to model.

Finally, the effectiveness of the ISO cavity radiation algorithms was examined by comparing results from these algorithms to detailed radiation calculations (from both programs). Our results suggest that improvements in cavity heat transfer calculations can be obtained by using detailed radiation modeling (i.e. view-factor or ray-tracing models), and that incorporation of these strategies may be more important for improving the accuracy of results than the use of CFD modeling for horizontal cavities.

%B 2007 ASHRAE Winter Meeting %C Dallas, TX %8 01/2007 %G eng %1

Windows and Daylighting Group

%2 LBNL-1132E %0 Conference Paper %B SimBuild 2006: Building Sustainability and Performance Through Simulation %D 2006 %T Evaluating Fenestration Products for Zero-Energy Buildings: Issues for Discussion %A Dariush K. Arasteh %A Dragan C. Curcija %A Yu Joe Huang %A Charlie Huizenga %A Christian Kohler %X

Computer modeling to determine fenestration product energy properties (U-factor, SHGC, VT) has emerged as the most cost-effective and accurate means to quantify them. Fenestration product simulation tools have been effective in increasing the use of low-e coatings and gas fills in insulating glass and in the widespread use of insulating frame designs and materials. However, for more efficient fenestration products (low heat loss products, dynamic products, products with non-specular optical characteristics, light redirecting products) to achieve widespread use, fenestration modeling software needs to be improved.

This paper addresses the following questions:

1) Are the current properties (U, SHGC, VT) calculated sufficient to compare and distinguish between windows suitable for Zero Energy Buildings and conventional window products? If not, what data on the thermal and optical performance, on comfort, and on peak demand of windows is needed.

2) Are the algorithms in the tools sufficient to model the thermal and optical processes? Are specific heat transfer and optical effects not accounted for? Is the existing level of accuracy enough to distinguish between products designed for Zero Energy Buildings? Is the current input data adequate?

%B SimBuild 2006: Building Sustainability and Performance Through Simulation %C Cambridge, MA %8 08/2006 %G eng %L LBNL-61249 %1

Windows and Daylighting Group

%2 LBNL-61249 %0 Conference Paper %B 2007 ASHRAE Winter Meeting %D 2006 %T Performance Criteria for Residential Zero Energy Windows %A Dariush K. Arasteh %A Howdy Goudey %A Yu Joe Huang %A Christian Kohler %A Robin Mitchell %X

This paper shows that the energy requirements for today's typical efficient window products (i.e. ENERGY STAR products) are significant when compared to the needs of Zero Energy Homes (ZEHs). Through the use of whole house energy modeling, typical efficient products are evaluated in five US climates and compared against the requirements for ZEHs. Products which meet these needs are defined as a function of climate. In heating dominated climates, windows with U-factors of 0.10 Btu/hr-ft2-F (0.57 W/m2-K) will become energy neutral. In mixed heating/cooling climates a low U-factor is not as significant as the ability to modulate from high SHGCs (heating season) to low SHGCs (cooling season).

%B 2007 ASHRAE Winter Meeting %C Dallas, TX %8 01/2007 %G eng %L LBNL-59190 %1

Windows and Daylighting Group

%2 LBNL-59190 %0 Report %D 2006 %T Window-Related Energy Consumption in the US Residential and Commercial Building Stock %A Joshua S. Apte %A Dariush K. Arasteh %X

We present a simple spreadsheet-based tool for estimating window-related energy consumption in the United States. Using available data on the properties of the installed US window stock, we estimate that windows are responsible for 2.15 quadrillion Btu (Quads) of heating energy consumption and 1.48 Quads of cooling energy consumption annually. We develop estimates of average U-factor and SHGC for current window sales. We estimate that a complete replacement of the installed window stock with these products would result in energy savings of approximately 1.2 quads. We demonstrate that future window technologies offer energy savings potentials of up to 3.9 Quads.

%G eng %L LBNL-60146 %1

Windows and Daylighting Group

%2 LBNL-60146 %0 Conference Paper %B 2006 ACEEE Summer Study on Energy Efficiency in Buildings %D 2006 %T Zero Energy Windows %A Dariush K. Arasteh %A Stephen E. Selkowitz %A Joshua S. Apte %A Marc LaFrance %X

Windows in the U.S. consume 30 percent of building heating and cooling energy, representing an annual impact of 4.1 quadrillion BTU (quads) of primary energy. Windows have an even larger impact on peak energy demand and on occupant comfort. An additional 1 quad of lighting energy could be saved if buildings employed effective daylighting strategies.

The ENERGY STAR(r) program has made standard windows significantly more efficient. However, even if all windows in the stock were replaced with today's efficient products, window energy consumption would still be approximately 2 quads. However, windows can be "net energy gainers" or "zero-energy" products. Highly insulating products in heating applications can admit more useful solar gain than the conductive energy lost through them. Dynamic glazings can modulate solar gains to minimize cooling energy needs and, in commercial buildings, allow daylighting to offset lighting requirements. The needed solutions vary with building type and climate. Developing this next generation of zero-energy windows will provide products for both existing buildings undergoing window replacements and products which are expected to be contributors to zero-energy buildings.

This paper defines the requirements for zero-energy windows. The technical potentials in terms of national energy savings and the research and development (R&D) status of the following technologies are presented:

Market transformation policies to promote these technologies as they emerge into the marketplace are then described.

%B 2006 ACEEE Summer Study on Energy Efficiency in Buildings %C Pacific Grove, CA %8 08/2006 %G eng %L LBNL-60049 %1

Windows and Daylighting Group

%2 LBNL-60049 %0 Report %D 2005 %T RESFEN5: Program Description %A Robin Mitchell %A Yu Joe Huang %A Dariush K. Arasteh %A Charlie Huizenga %A Steve Glendenning %X

A computer tool such as RESFEN can help consumers and builders pick the most energy-efficient and cost-effective window for a given application, whether it is a new home, an addition, or a window replacement. It calculates heating and cooling energy use and associated costs as well as peak heating and cooling demand for specific window products. Users define a specific scenario by specifying house type (single-story or two-story), geographic location, orientation, electricity and gas cost, and building configuration details (such as wall, floor, and HVAC system type). Users also specify size, shading, and thermal properties of the window they wish to investigate. The thermal properties that RESFEN requires are: U-factor, Solar Heat Gain Coefficient, and air leakage rate. RESFEN calculates the energy and cost implications of the window compared to an insulated wall. The relative energy and cost impacts of two different windows can be compared.

RESFEN 3.0 was a major improvement over previous versions because it performs hourly calculations using a version of the DOE 2.1E (LBL 1980, Winkelmann et al. 1993) energy analysis simulation program. RESFEN 3.1 incorporates additional improvements including input assumptions for the base case buildings taken from the National Fenestration Rating Council (NFRC) Annual Energy Subcommittee's efforts.

%I Lawrence Berkeley National Laboratory %8 05/2005 %G eng %1

Windows and Daylighting Group

%2 LBNL-812E %0 Conference Paper %B 2005 ASHRAE Winter Meeting %D 2005 %T Two-Dimension Conduction and CFD Simulations for Heat Transfer in Horizontal Window Frame Cavities %A Arlid Gustavsen %A Dariush K. Arasteh %A Christian Kohler %A Dragan C. Curcija %X

Accurately analyzing heat transfer in window frames and glazings is important for developing and characterizing the performance of highly insulating window products. This paper uses computational fluid dynamics (CFD) modeling to assess the accuracy of the simplified frame cavity conduction/convection models presented in ISO 15099 and used in software for rating and labeling window products. Three representative complex cavity cross-section profiles with varying dimensions and aspect ratios are examined. The results presented support the ISO 15099 rule that complex cavities with small throats should be subdivided; however, our data suggest that cavities with throats smaller than 7 mm should be subdivided, in contrast to the ISO 15099 rule, which places the break point at 5 mm. The agreement between CFD modeling results and the results of the simplified models is moderate for the heat transfer rates through the cavities. The differences may be a result of the underlying ISO 15099 Nusselt number correlations being based on studies where cavity height/length aspect ratios were smaller than 0.5 and greater than 5 (with linear interpolation assumed in between). The results presented here are for horizontal frame members because convection in vertical jambs involves very different aspect ratios that require three-dimensional CFD simulations.

%B 2005 ASHRAE Winter Meeting %C Orlando, FL %V 111 %8 02/2005 %G eng %L LBNL-61250 %1

Windows and Daylighting Group

%2 LBNL-61250 %0 Conference Paper %B SimBuild 2004 %D 2004 %T Development of Trade-Off Equations for EnergyStar Windows %A Yu Joe Huang %A Robin Mitchell %A Stephen E. Selkowitz %A Dariush K. Arasteh %A Robert D. Clear %X

The authors explore the feasibility of adding a performance option to DOE's EnergyStar© Windows program whereby windows of differing U-factors and SHGCs can qualify so long as they have equivalent annual energy performance. An iterative simulation procedure is used to calculate trade-off equations giving the change in SHGC needed to compensate for a change in U-factor. Of the four EnergyStar© Window climate zones, trade-off equations are possible only in the Northern and Southern zones. In the North/Central and South/Central zones, equations are not possible either because of large intrazone climate variations or the current SHGC requirements are already near optimum.

%B SimBuild 2004 %C Boulder, CO %8 08/2004 %G eng %L LBNL-55517 %1

Windows and Daylighting Group

%2 LBNL-55517 %0 Report %D 2004 %T A First-Generation Prototype Dynamic Residential Window %A Christian Kohler %A Howdy Goudey %A Dariush K. Arasteh %X

We present the concept for a "smart" highly efficient dynamic window that maximizes solar heat gain during the heating season and minimizes solar heat gain during the cooling season in residential buildings. We describe a prototype dynamic window that relies on an internal shade, which deploys automatically in response to solar radiation and temperature. This prototype was built at Lawrence Berkeley National Laboratory from commercially available "off-the-shelf" components. It is a stand-alone, standard-size product, so it can be easily installed in place of standard window products. Our design shows promise for near-term commercialization. Improving thermal performance of this prototype by incorporating commercially available highly efficient glazing technologies could result in the first window that could be suitable for use in zero-energy homes. The units predictable deployment of shading could help capture energy savings that are not possible with manual shading. Installation of dynamically shaded windows in the field will allow researchers to better quantify the energy effects of shades, which could lead to increased efficiency in the sizing of heating, ventilation, and air conditioning equipment for residences.

%P 11 %8 10/2004 %G eng %L LBNL-56075 %1

Windows and Daylighting Group

%2 LBNL-56075 %0 Book %D 2004 %T Window Systems for High-Performance Buildings %A John Carmody %A Stephen E. Selkowitz %A Eleanor S. Lee %A Dariush K. Arasteh %X

A guide to essential window design issues, technologies, and applications for designers, specifiers, and builders.

The challenge in designing facades and selecting windows in commercial buildings is balancing many issues and criteria. This fact-packed guide outlines the basics of glazing selection and provides critical information and performance data on the energy efficiency, interior environment, technical, and life-cycle-cost considerations that drive window design decisions in commercial buildings.

%I W. W. Norton & Company, Inc., %C New York, NY %P 400 %8 04/2004 %@ 978-0-393-73121-7 %0 Report %D 2003 %T THERM 5/WINDOW 5 NFRC Simulation Manual %A Robin Mitchell %A Christian Kohler %A Dariush K. Arasteh %A John Carmody %A Charlie Huizenga %A Dragan C. Curcija %X

This document, the THERM 5 / WINDOW 5 NFRC Simulation Manual, discusses how to use the THERM and WINDOW programs to model products for NFRC certified simulations and assumes that the user is already familiar with those programs. In order to learn how to use these programs, it is necessary to become familiar with the material in both the THERM Users Manual and the WINDOW Users Manual. In general, this manual references the Users Manuals rather than repeating the information.

If there is a conflict between either of the User Manual and this THERM 5 / WINDOW 5 NFRC Simulation Manual, the THERM 5 / WINDOW 5 NFRC Simulation Manual takes precedence. In addition, if this manual is in conflict with any NFRC standards, the standards take precedence. For example, if samples in this manual do not follow the current taping and testing NFRC standards, the standards not the samples in this manual, take precedence.

%G eng %L LBNL-48255 %1

Windows and Daylighting Group

%2 LBNL-48255 %0 Conference Paper %B ASHRAE Winter Meeting %D 2003 %T Two-Dimensional Computational Fluid Dynamics and Conduction Simulations of Heat Transfer in Window Frames with Internal Cavities - Part 1: Cavities Only %A Arlid Gustavsen %A Christian Kohler %A Dariush K. Arasteh %A Dragan C. Curcija %X

Accurately analyzing heat transfer in window frame cavities is essential for developing and characterizing the performance of highly insulating window products. Window frame thermal performance strongly influences overall product thermal performance because framing materials generally perform much more poorly than glazing materials. This paper uses Computational Fluid Dynamics (CFD) modeling to assess the accuracy of the simplified frame cavity conduction/convection models presented in ISO 15099 and used in software for rating and labeling window products. (We do not address radiation heat-transfer effects.) We examine three representative complex cavity cross-section profiles with varying dimensions and aspect ratios. Our results support the ISO 15099 rule that complex cavities with small throats should be subdivided; however, our data suggest that cavities with throats smaller than seven millimeters (mm) should be subdivided, in contrast to the ISO 15099 rule, which places the break point at five mm. The agreement between CFD modeling results and the results of the simplified models is moderate. The differences in results may be a result of the underlying ISO correlations being based on studies where cavity height/length (H/L) aspect ratios were smaller than 0.5 and greater than five (with linear interpolation assumed in between). The results presented here are for horizontal frame members because convection in vertical jambs involves very different aspect ratios that require three-dimensional CFD simulations. Ongoing work focuses on quantifying the exact effect on window thermal performance indicators of using the ISO 15099 approximations in typical real window frames.

%B ASHRAE Winter Meeting %C Orlando, FL %8 02/2005 %G eng %L LBNL-52509 %1

Windows and Daylighting Group

%2 LBNL-52509 %0 Report %D 2002 %T A Characterization of the Nonresidential Fenestration Market %A Arman Shehabi %A Charles N. Eley %A Dariush K. Arasteh %A Phil Degens %X

The purpose of this report is to characterize the nonresidential fenestration market in order to better understand market barriers to, and opportunities for, energy-efficient fenestration products. In particular, the goal is to:

The U.S. glass industry is a $27 billion enterprise with both large producers and small firms playing pivotal roles in the industry. While most sectors of the glass industry have restructured and consolidated in the past 20 years, the industry still employs 150,000 workers. Nonresidential glazing accounts for approximately 18% of overall U.S. glass production. In 1999, nonresidential glazing was supplied to approximately 2.2 billion ft2 of new construction and additions. That same year, nonresidential glazing was also supplied to approximately 1.1 billion ft2 of remodeling construction. With an industry this large and complex, it is to be expected that many market participants can influence fenestration selection. If market barriers to the selection of high performance fenestration products are better understood, then the U. S. Department of Energy (USDOE), the Northwest Energy Efficiency Alliance (NEEA), and others can develop programs and policies that promote greater energy efficiency in commercial glazing products.

%G eng %L LBNL-52699 %1

Windows and Daylighting Group

%2 LBNL-52699 %0 Conference Paper %B 2002 ACEEE Summer Study on Energy Efficiency in Buildings %D 2002 %T Energy Efficient Windows in the Southern Residential Windows Market %A Alison Tribble %A Kate Offringa %A Bill Prindle %A Dariush K. Arasteh %A Jay Zarnikau %A Arlene Stewart %A Ken Nittler %X

The greatest potential in the U.S. for cost-effective energy savings from currently available energy efficient residential windows and skylights exists in the southern market. Prindle and Arasteh recently reported that ten southern states could save over 400 million kwh and 233 MW of peak electricity generating capacity annually by adopting the International Energy Conservation Code (IECC) standard of 0.40 (or less) solar heat gain coefficient (SHGC) for new construction (Prindle & Arasteh 2001). In 2000, Anello et al. demonstrated savings of 14.7 percent in reduced cooling load with high-performance windows (Anello et al. 2000). In 2002, Wilcox demonstrated savings of 20 percent while simulation analysis estimates cooling energy savings in the 30 percent range (Wilcox 2002).

In the southern market, there is significant opportunity for reducing cooling energy use with low solar gain low-E windows. Yet, the southern market has been slow to embrace this new technology. Market research shows that while low-E products have achieved up to 70 percent of the market share in some colder climates (Jennings, Degens & Curtis 2002), they have gained less than 10 percent of the southern windows market (Prindle & Arasteh 2001).

This paper will explore the residential windows market by considering the following: market barriers unique to the southern market; distribution channels in the South; the roles of utilities, codes officials, and other organizations; and other indirect factors that influence this market. This paper will profile current market transformation efforts with case studies of the Florida Windows Initiative, sponsored by the Efficient Windows Collaborative at the Alliance to Save Energy, and the Texas Windows Initiative, sponsored by the American Electric Power Company. Finally, this paper will identify the next steps that will be critical to transforming the southern residential windows market to more efficient window and skylight products.

%B 2002 ACEEE Summer Study on Energy Efficiency in Buildings %C Pacific Grove, CA %8 08/2002 %G eng %L LBNL-51425 %1

Windows and Daylighting Group

%2 LBNL-51425 %0 Report %D 2002 %T Energy Savings and Pollution Prevention Benefits of Solar Heat Gain Standards in the International Energy Conservation Code %A Bill Prindle %A Dariush K. Arasteh %X

The International Energy Conservation Code (IECC), published by the International Code Council, the code development orgalization of building code officials, contains new provisions that save energy and reduce air pollution emissions. Its most significant new provision is a prescriptive standard for solar heat gain control in windows in wanner climate zones. Because solar heat gain through windows is one of the largest components of residential cooling loads, this standard reduces cooling loads dramatically, which in turn reduces electricity consumption, utility bills, and powerplant pollution emissions. It can also reduce the size of cooling equipment, a capital cost saving that can offset increased costs for the higher performance windows needed to meet the standard.

This paper documents the potential energy efficiency, dollar, and pollution reduction benefits of the IECCs solar heat gain standard. Using the RESFEN model developed at Lawrence Berkeley National Laboratory, we simulated a typical new home in ten southern states that would be affected the new IECC solar heat gain standard. Our analysis found that in these ten states, adoption of the IECC in its first year could save 400 million kWh, $38 million in electric bills, and 233 MW of peak electricity generating capacity. The cumulative savings from these homes in year 20 would rise to 80 billion kwh, $7.6 billion in electricity bills, and 4,660 Megawatts of generating capacity. In year twenty, the electric energy savings would also prevent the emission of 20,000 tons of NOx and over 1.5 million tons of carbon equivalent.

Extrapolating the calculations in this paper to include other states with significant cooling load reduction from the IECC leads us to believe peak savings from new construction will total 300MW annually. Given that the window replacement and remodeling market is slightly larger than the new construction market (and here the baseline is poorer performing single glazing), leads to the conclusion that savings which include the remodeling and replacement market should exceed 600MW annually. This would eliminate the need to build two average sized 300MW power plants every year. Additional, similar savings could also be expected from applying this technology to windows in commercial buildings, although we have not accounted for these savings in these estimates.

%G eng %L LBNL-51426 %1

Windows and Daylighting Group

%2 LBNL-51426 %0 Report %D 2002 %T An Evaluation of Alternative Qualifying Criteria for Energy Star Windows %A Ed Barbour %A Dariush K. Arasteh %X

Energy Star is a voluntaly partnership between the U.S. Department of Energy (DOE), the U.S. Environmental Protection Agency (EPA), and industry. Energy Star, at both DOE andsEPA, is based on legislative mandates to implement voluntary, non-regulatory programs to promote products that are substantially more efficient than required by Federal standards (the DOE Energy Star program originated with Section 127 of the Energy Policy Act of 1992 (EPACT), and the EPA Energy Star program originated with Section 103 of the CleansAir Act amendments of 1990). The base criteria under EPACT requires DOE to establish voluntary energy efficiency product programs that serve to increase the technical energy performance potential of products, are cost-effective for the consumer, save energy and thus reduce green house gas emissions. Criteria used by EPA under the Clean Air Act are similar but reflect a greater emphasis on reducing green house gas emissions.

The primary objective of the partnership is to expand the market for energy-efficient products. EPA and DOE use the Energy Star label to recognize and promlote the most energy-efficient subset of the market. The label is a simple mechanism that allows consumers to easily identify the most energy-efficient products in the marketplace. In developing specifications for the Energy Star label, EPA and DOE consider several key factors, including:

%8 05/2002 %G eng %1

Windows and Daylighting Group

%2 LBNL-51427 %0 Conference Paper %B ASHRAE Transactions %D 2002 %T Future Advanced Windows for Zero-Energy Homes %A Joshua S. Apte %A Dariush K. Arasteh %A Yu Joe Huang %X

Over the past 15 years, low-emissivity and other technological improvements have significantly improved the energy efficiency of windows sold in the United States. However, as interest increases in the concept of zero-energy homes—buildings that do not consume any nonrenewable or net energy from the utility grid—even today's highest-performance window products will not be sufficient. This simulation study compares today's typical residential windows, today's most efficient residential windows, and several options for advanced window technologies, including products with improved fixed or static properties and products with dynamic solar heat gain properties. Nine representative window products are examined in eight representative U.S. climates. Annual energy and peak demand impacts are investigated. We conclude that a new generation of window products is necessary for zero-energy homes if windows are not to be an energy drain on these homes. Windows with dynamic solar heat gain properties are found to offer significant potential in reducing energy use and peak demands in northern and central climates, while windows with very low (static) solar heat gain properties offer the most potential in southern climates.

%B ASHRAE Transactions %C Kansas City, MO %V 109, pt 2 %P 871-888 %8 06/2003 %G eng %L LBNL-51913 %1

Windows and Daylighting Group

%2 LBNL-51913 %0 Conference Paper %B Performance of Exterior Envelopes of Whole Buildings VIII %D 2001 %T Improving Information Technology to Maximize Fenestration Energy Efficiency %A Dariush K. Arasteh %A Robin Mitchell %A Christian Kohler %A Charlie Huizenga %A Dragan C. Curcija %X

Annual heating and cooling energy loads through fenestration products in both residential and commercial buildings are a significant fraction of national energy requirements. In the residential sector, 1.34 and 0.37 quads are required for heating and cooling respectively (DOE Core Data Book, 2000). In commercial buildings, cooling energy use to compensate for fenestration product solar heat gain is estimated at 0.39 quads; heating energy use to compensate for heat loss through fenestration products is estimated at 0.19 quads. Advanced products offer the potential to reduce these energy uses by at least 50% (Frost et. al. 1993). Potential electric lighting savings from fenestration products are estimated at 0.4 quads if daylight can be used effectively so that electric lighting in commercial building perimeter zones can be reduced.

Software has begun to make an impact on the design and deployment of efficient fenestration products by making fenestration product performance ratings widely available. These ratings, which are determined in part using software programs such as WINDOW/THERM/Optics, VISION/FRAME, and WIS, can now easily be used by architects, engineers, professional fenestration product specifiers, and consumers. Information on the properties of fenestration products has also influenced state and national codes (IECC, ASHRAE 90.1) and aided voluntary market transformation programs, such as the Efficient Windows Collaborative and the Energy Star Windows program, which promote efficient fenestration products.

%B Performance of Exterior Envelopes of Whole Buildings VIII %C Clearwater Beach, FL %8 12/2001 %G eng %L LBNL-48147 %1

Windows and Daylighting Group

%2 LBNL-48147 %0 Conference Paper %B ASHRAE Seminar %D 2001 %T Infrared Thermography Measurements of Window Thermal Test Specimen: Surface Temperatures %A Brent T. Griffith %A Howdy Goudey %A Dariush K. Arasteh %X

Temperature distribution data are presented for the warm-side surface of three different window specimens. The specimens were placed between warm and cold environmental chambers that were operated in steady state at two different standard design conditions for winter heating. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) temperature conditions were 21.1 deg. C (70 deg. F) and -17.8 deg. C (0 deg. F) on the warm and cold sides, respectively. The International Standards Organization (ISO) temperature conditions were 20.0 deg. C (68.0 deg. F) and 0.0 deg. C (32.0 deg. F) on the warm and cold sides, respectively. Surface temperature maps were compiled using an infrared thermographic system with an external referencing technique, a traversing point infrared thermometer and thermocouples. The infrared techniques allow detailed, non-intrusive mapping of surface temperatures. Surface temperature data are plotted for the vertical distribution along the centerline of the window specimen. This paper is part of larger round-robin collaborative effort that studied this same set of window specimens. These studies were conducted to improve and check the accuracy of computer simulations for predicting the condensation resistance of window products. Data collected for a Calibrated Transfer Standard showed that convective effects outside the window gap are important for predicting surface temperatures.

%B ASHRAE Seminar %C Atlantic City, NJ %8 01/2002 %G eng %L LBNL-47373 %1

Windows and Daylighting Group

%2 LBNL-47373 %0 Report %D 2001 %T The Integrated Energy-Efficiency Window-Wall System %A Michael Arney %A James Fairman %A John Carmody %A Dariush K. Arasteh %G eng %1

Windows and Daylighting Group

%2 LBNL-51466 %0 Journal Article %J ASHRAE Transactions %D 2001 %T THERM Simulations of Window Indoor Surface Temperatures for Predicting Condensation %A Christian Kohler %A Dariush K. Arasteh %A Robin Mitchell %X

As part of a round robin project, the performance of two wood windows and a Calibrated Transfer Standard was modeled using the THERM heat-transfer simulation program. The resulting interior surface temperatures can be used as input to condensation resistance rating procedures. The Radiation and Condensation Index features within THERM were used to refine the accuracy of simulation results. Differences in surface temperatures between the Basic calculations and those incorporating the Radiation and/or Condensation Index features are demonstrated and explained.

%B ASHRAE Transactions %C Atlantic City, NJ %V 109, Part 1 %P 593-599 %8 01/ 2002 %G eng %1

Windows and Daylighting Group

%2 LBNL-47962 %0 Report %D 2001 %T WINDOW 5.0 User Manual for Analyzing Window Thermal Performance %A Robin Mitchell %A Christian Kohler %A Dariush K. Arasteh %A Charlie Huizenga %A Dragan C. Curcija %G eng %1

Windows and Daylighting Group

%2 LBNL-44789 %0 Journal Article %J ASHRAE Transactions %D 2000 %T Natural Convection Effects in Three-Dimensional Window Frames with Internal Cavities %A Arlid Gustavsen %A Brent T. Griffith %A Dariush K. Arasteh %X

This paper studies three-dimensional natural convection effects in window frames with internal cavities. Infrared (IR) thermography experiments, computational fluid dynamics (CFD) simulations, and calculations with traditional software for simulating two-dimensional heat conduction were conducted. The IR thermography experiments mapped surface temperatures during steady-state thermal tests between ambi-ent thermal chambers set at 0 deg. C and 20 deg. C. Using anon-contact infrared scanning radiometer and an external referencing technique, we were able to obtain surface temperature maps with a resolution of 0.1 deg. C and 3 mm and an estimated uncertainty of 0.5 deg. C and +/-3 mm. The conjugate CFD simulations modeled the enclosed air cavities, frame section walls, and foam board surround panel. With the two-dimensional heat conduction simulation software, weusedcorrelations to model heat transfer in the air cavities. For both the CFD simulations and the conduction simulation software, boundary conditions at the external air/solid interface were modeled using constant surface heat-transfer coefficients with fixed ambient air temperatures.

Different cases were studied, including simple, four-sided frame sections (with one open internal cavity), simple vertical sections with a single internal cavity, and horizontal sections with a single internal cavity. The sections tested in the Infrared Thermography Laboratory (IR lab) were made of PVC. Both PVC and thermally broken aluminum sections were modeled. Based on the current investigations, it appears that the thermal transmittance or U-factor of a four-sided section can be found by calculating the average of the thermal transmittance of the respective single horizontal and vertical sections. In addition, we conclude that two-dimensional heat transfer simulation software agrees well with CFD simulations if the natural convection correlations used for the internal cavities are correct.

%B ASHRAE Transactions %C Cincinnati, Ohio %V 107, Part 2 %8 06/2001 %G eng %1

Windows and Daylighting Group

%2 LBNL-47073 %0 Report %D 2000 %T THERM 2.1 NFRC Simulation Manual %A Robin Mitchell %A Christian Kohler %A Dariush K. Arasteh %A Elizabeth U. Finlayson %A Charlie Huizenga %A Dragan C. Curcija %A John Carmody %X

This document, the THERM 2.1 NFRC Simulation Manual, discusses how to use THERM to model products for NFRC certified simulations and assumes that the user is already familiar with the THERM program. In order to learn how to use THERM, it is necessary to become familiar with the material in the THERM User's Manual.

In general, this manual references the THERM User's Manual rather than repeating the information.

If there is a conflict between the THERM User's Manual and the THERM 2.1 NFRC Simulation Manual, the THERM 2.1 NFRC Simulation Manual takes precedence.

%P 260 %8 07/2000 %G eng %1

Windows and Daylighting Group

%2 PUB-3147 %0 Journal Article %J ASHRAE Transactions %D 2000 %T Three-Dimensional Conjugate Computational Fluid Dynamics Simulations of Internal Window Frame Cavities Validated Using IR Thermography %A Arlid Gustavsen %A Brent T. Griffith %A Dariush K. Arasteh %X

This paper studies the effectiveness of one commercial computational fluid dynamics (CFD) program for simulating combined natural convection and heat transfer in three dimensions for air-filled cavities similar to those found in the extruded frame sections of windows. The accuracy of the conjugate CFD simulations is evaluated by comparing results for surface temperature on the warm side of the specimens to results from experiments that use infrared (IR) thermography to map surface temperatures during steady-state thermal tests between ambient thermal chambers set at 0 °C and 20 °C. Validations using surface temperatures have been used in previous studies of two-dimensional simulations of glazing cavities with generally good results. Using the techniques presented and a noncontact infrared scanning radiometer we obtained surface temperature maps with a resolution of 0.1 °C and 3 mm and an estimated uncertainty of +/-0.5 °C and +/-3mm. Simulation results are compared to temperature line and contour plots for the warm side of the specimen. Six different cases were studied, including a simple square section in a single vertical cavity and two four-sided frame cavities as well as more complex H- and U-shaped sections. The conjugate CFD simulations modeled the enclosed air cavities, the frame section walls, and the foam board surround panel. Boundary conditions at the indoor and outdoor air/solid interface were modeled using constant surface heat-transfer coefficients with fixed ambient-air temperatures. In general, there was good agreement between the simulations and experiments, although the accuracy of the simulations is not explicitly quantified. We conclude that such simulations are useful for future evaluations of natural convection heat transfer in frame cavities.

%B ASHRAE Transactions %C Cincinnati, Ohio %V 107 %P 538-549 %8 06/2001 %G eng %N 2 %L LBNL-46825 %1

Windows and Daylighting Group

%2 LBNL-46825 %0 Conference Paper %B 2000 ASHRAE Winter Meeting %D 1999 %T A Database of Window Annual Energy Use in Typical North American Residences %A Dariush K. Arasteh %A Yu Joe Huang %A Robin Mitchell %A Robert D. Clear %A Christian Kohler %X

This paper documents efforts by the National Fenestration Rating Council to develop a database on annual energy impacts of windows in a typical new, single family, single story residence in various U.S. and Canadian climates. The result is a database of space heating and space cooling energies for 14 typical windows in 52 North American climates. (Future efforts will address the effects of skylights.) This paper describes how this database was created, documents the assumptions used in creating this database, elaborates on assumptions, which need further research, examines the results, and describes the possible uses of the database.

%B 2000 ASHRAE Winter Meeting %C Dallas, Texas %8 02/2000 %G eng %L LBNL-44020 %1

Windows and Daylighting Group

%2 LBNL-44020 %0 Report %D 1999 %T RESFEN 3.1: A PC Program for Calculating the Heating and Cooling Energy Use of Windows in Residential Buildings %A Robin Mitchell %A Yu Joe Huang %A Dariush K. Arasteh %A Robert Sullivan %A Santosh Phillip %X

A computer tool such as RESFEN can help consumers and builders pick the most energy-efficient and cost-effective window for a given application, whether it is a new home, an addition, or a window replacement. It calculates heating and cooling energy use and associated costs as well as peak heating and cooling demand for specific window products. Users define a specific scenario by specifying house type (single-story or two-story), geographic location, orientation, electricity and gas cost, and building configuration details (such as wall, floor, and HVAC system type). Users also specify size, shading, and thermal properties of the window they wish to investigate. The thermal properties that RESFEN requires are: U-factor, Solar Heat Gain Coefficient, and air leakage rate. RESFEN calculates the energy and cost implications of the window compared to an insulated wall. The relative energy and cost impacts of two different windows can be compared.

RESFEN 3.0 was a major improvement over previous versions because it performs hourly calculations using a version of the DOE 2.1E (LBL 1980, Winkelmann et al. 1993) energy analysis simulation program. RESFEN 3.1 incorporates additional improvements including input assumptions for the base case buildings taken from the National Fenestration Rating Council (NFRC) Annual Energy Subcommittee's efforts.

%I Lawrence Berkeley National Laboratory %C Berkeley %8 08/1999 %G eng %1

Windows and Daylighting Group

%2 LBNL-40682 Rev. %0 Conference Paper %B Thermal Performance of the Exterior Envelopes of Buildings VII %D 1999 %T Residential Fenestration Performance Analysis Using RESFEN 3.1 %A Yu Joe Huang %A Robin Mitchell %A Dariush K. Arasteh %A Stephen E. Selkowitz %X

This paper describes the development efforts of RESFEN 3.1, a PC-based computer program for calculating the heating and cooling energy performance and cost of residential fenestration systems. The development of RESFEN has been coordinated with ongoing efforts by the National Fenestration Rating Council (NFRC) to develop an energy rating system for windows and skylights to maintain maximum consistency between RESFEN and NFRCs planned energy rating system. Unlike previous versions of RESFEN, that used regression equations to replicate a large data base of computer simulations, Version 3.1 produces results based on actual hour-by-hour simulations. This approach has been facilitated by the exponential increase in the speed of personal computers in recent years. RESFEN 3.1 has the capability of analyzing the energy performance of windows in new residential buildings in 52 North American locations. The user describes the physical, thermal and optical properties of the windows in each orientation, solar heat gain reductions due to obstructions, overhangs, or shades, and the location of the house. The RESFEN program then models a prototypical house for that location and calculates the energy use of the house using the DOE-2 program. The user can vary the HVAC system, foundation type, and utility costs. Results are presented for the annual heating and cooling energy use, energy cost, and peak energy demand of the house, and the incremental energy use or peak demand attributable to the windows in each orientation. This paper describes the capabilities of RESFEN 3.1, its usefulness in analyzing the energy performance of residential windows and its development effort and gives insight into the structure of the computer program. It also discusses the rationale and benefits of the approach taken in RESFEN in combining a simple-to-use graphical front-end with a detailed hour-by-hour simulation engine to produce an energy analysis tool for the general public that is user-friendly yet highly accurate.

%B Thermal Performance of the Exterior Envelopes of Buildings VII %C Clearwater Beach, FL %8 12/1998 %G eng %L LBNL-42871 %1

Simulation Research Group

%2 LBNL-42871 %0 Conference Paper %B Building Simulation 99, International Building Performance Simulation Association (IBPSA) %D 1999 %T THERM 2.0: A Building Component Model for Steady-State Two-Dimensional Heat Transfer %A Charlie Huizenga %A Dariush K. Arasteh %A Elizabeth U. Finlayson %A Robin Mitchell %A Brent T. Griffith %A Dragan C. Curcija %X

THERM 2.0 is a state-of-the-art software program, available without cost, that uses the finite-element method to model steady-state, two-dimensional heat-transfer problems. It includes a powerful simulation engine combined with a simple, interactive interface and graphic results. Although it was developed primarily to model thermal properties of windows, it is appropriate for other building components such as walls, doors, roofs, and foundations, and is useful for modeling thermal bridges in many other contexts, such as the design of equipment.

%B Building Simulation 99, International Building Performance Simulation Association (IBPSA) %C Kyoto, Japan %8 09/1999 %G eng %L LBNL-43991 %1

Windows and Daylighting Group

%2 LBNL-43991 %0 Conference Paper %B Thermal Performance of the Exterior Envelopes of Buildings VII %D 1998 %T Experimental Techniques for Measuring Temperature and Velocity Fields to Improve the Use and Validation of Building Heat Transfer Models %A Brent T. Griffith %A Daniel Turler %A Howdy Goudey %A Dariush K. Arasteh %X

When modeling thermal performance of building components and envelopes, researchers have traditionally relied on average surface heat-transfer coefficients that often do not accurately represent surface heat-transfer phenomena at any specific point on the component being evaluated. The authors have developed new experimental techniques that measure localized surface heat-flow phenomena resulting from convection. The data gathered using these new experimental procedures can be used to calculate local film coefficients and validate complex models of room and building envelope heat flows. These new techniques use a computer controlled traversing system to measure both temperatures and air velocities in the boundary layer near the surface of a building component, in conjunction with current methods that rely on infrared (IR) thermography to measure surface temperatures. Measured data gathered using these new experimental procedures are presented here for two specimens: (1) a Calibrated Transfer Standard (CTS) that approximates a constant-heat-flux, flat plate; and (2) a dual-glazed, low-emittance (low-e), wood-frame window. The specimens were tested under steady-state heat flow conditions in laboratory thermal chambers. Air temperature and mean velocity data are presented with high spatial resolution (0.25- to 25-mm density). Local surface heat-transfer film coefficients are derived from the experimental data by means of a method that calculates heat flux using a linear equation for air temperature in the inner region of the boundary layer. Local values for convection surface heat-transfer rate vary from 1 to 4.5 W/m2K. Data for air velocity show that convection in the warm-side thermal chamber is mixed forced/natural, but local velocity maximums occur from 4 to 8 mm from the window glazing.

%B Thermal Performance of the Exterior Envelopes of Buildings VII %C Clearwater Beach, FL %8 12/1998 %G eng %L LBNL-41772 %1

Windows and Daylighting Group

%2 LBNL-41772 %0 Conference Paper %B ASHRAE/DOE/BTECC Conference, Thermal Performance of the Exterior Envelopes of Buildings VII %D 1998 %T Rapid field testing of low-emittance coated glazings for product verification %A Brent T. Griffith %A Christian Kohler %A Howdy Goudey %A Daniel Turler %A Dariush K. Arasteh %X

This paper analyzes prospects for developing a test device suitable for field verification of the types of low-emittance (low-e) coatings present on high-performance window products. Test devices are currently available that can simply detect the presence of low-e coatings and that can measure other important characteristics of high-performance windows, such as the thickness of glazing layers or the gap in dual glazings. However, no devices have yet been developed that can measure gas concentrations or distinguish among types of coatings. This paper presents two optical methods for verification of low-e coatings. The first method uses a portable, fiber-optic spectrometer to characterize spectral reflectances from 650 to 1,100 nm for selected surfaces within an insulated glazing unit (IGU). The second method uses an infrared-light-emitting diode and a phototransistor to evaluate the aggregate normal reflectance of an IGU at 940 nm. Both methods measure reflectance in the near (solar) infrared spectrum and are useful for distinguishing between regular and spectrally selective low-e coatings. The infrared-diode/phototransistor method appears promising for use in a low-cost, hand-held field test device.

%B ASHRAE/DOE/BTECC Conference, Thermal Performance of the Exterior Envelopes of Buildings VII %C Clearwater Beach, Florida %8 12/1998 %G eng %L LBNL-41352 %1

Windows and Daylighting Group

%2 LBNL-41352 %0 Conference Paper %B ACEEE 1998 Summer Study on Energy Efficiency in Buildings %D 1998 %T State-of-the-Art Software for Window Energy-Efficiency Rating and Labeling %A Dariush K. Arasteh %A Elizabeth U. Finlayson %A Yu Joe Huang %A Charlie Huizenga %A Robin Mitchell %A Michael D. Rubin %X

Measuring the thermal performance of windows in typical residential buildings is an expensive proposition. Not only is laboratory testing expensive, but each window manufacturer typically offers hundreds of individual products, each of which has different thermal performance properties. With over a thousand window manufacturers nationally, a testing-based rating system would be prohibitively expensive to the industry and to consumers.

Beginning in the early 1990s, simulation software began to be used as part of a national program for rating window U-values. The rating program has since been expanded to include Solar Hear Gain Coefficients and is now being extended to annual energy performance.

This paper describes four software packages available to the public from Lawrence Berkeley National Laboratory (LBNL). These software packages are used to evaluate window thermal performance: RESFEN (for evaluating annual energy costs), WINDOW (for calculating a products thermal performance properties), THERM (a preprocessor for WINDOW that determines two-dimensional heat-transfer effects), and Optics (a preprocessor for WINDOWs glass database).

Software not only offers a less expensive means than testing to evaluate window performance, it can also be used during the design process to help manufacturers produce windows that will meet target specifications. In addition, software can show small improvements in window performance that might not be detected in actual testing because of large uncertainties in test procedures.

%B ACEEE 1998 Summer Study on Energy Efficiency in Buildings %C Pacific Grove, CA %8 08/1998 %G eng %L LBNL-42151 %1

Windows and Daylighting Group

%2 LBNL-42151 %0 Journal Article %J ASHRAE Transactions %D 1998 %T Teaching Students about Two-Dimensional Heat Transfer Effects in Buildings, Building Components, Equipment, and Appliances Using THERM 2.0 %A Charlie Huizenga %A Dariush K. Arasteh %A Elizabeth U. Finlayson %A Robin Mitchell %A Brent T. Griffith %X

THERM 2.0 is a state-of-the-art software program, available for free, that uses the finite-element method to model steady-state, two-dimensional heat-transfer effects. It is being used internationally in graduate and undergraduate laboratories and classes as an interactive educational tool to help students gain a better understanding of heat transfer. THERM offers students a powerful simulation engine combined with a simple, interactive interface and graphic results. Although it was developed to model thermal properties of building components such as windows, walls, doors, roofs, and foundations, it is useful for modeling thermal bridges in many other contexts, such as the design of equipment. These capabilities make THERM a useful teaching tool in classes on: heating, ventilation, and air-conditioning (HVAC); energy conservation; building design; and other subjects where heat-transfer theory and applications are important. THERMs state-of-the-art interface and graphic presentation allow students to see heat-transfer paths and to learn how changes in materials affect heat transfer. THERM is an excellent tool for helping students understand the practical application of heat-transfer theory.

%B ASHRAE Transactions %C Chicago, IL %V 105, Part 1 %8 01/1999 %G eng %L LBNL-42102 %1

Windows and Daylighting Group

%2 LBNL-42102 %0 Report %D 1998 %T THERM 2.0: a PC Program for Analyzing Two-Dimensional Heat Transfer through Building products %A Elizabeth U. Finlayson %A Robin Mitchell %A Dariush K. Arasteh %A Charlie Huizenga %A Dragan C. Curcija %X

THERM is a state-of-the-art, Microsoft Windows?-based computer program developed at Lawrence Berkeley National Laboratory (LBNL) for use by building component manufacturers, engineers, educators, students, architects, and others interested in heat transfer. Using THERM, you can model two-dimensional heat-transfer effects in building components such as windows, walls, foundations, roofs, and doors; appliances; and other products where thermal bridges are of concern. THERM's heat-transfer analysis allows you to evaluate a product?s energy efficiency and local temperature patterns, which may relate directly to problems with condensation, moisture damage, and structural integrity.

This version of THERM includes several new technical and user interface features; the most significant is a radiation view-factor algorithm. This feature increases the accuracy of calculations in situations where you are analyzing non-planar surfaces that have different temperatures and exchange energy through radiation heat transfer. This heat-transfer mechanism is important in greenhouse windows, hollow cavities, and some aluminum frames.

%G eng %L LBL-37371 Rev. 2 %1

Windows and Daylighting Group

%2 LBL-37371R %0 Journal Article %J ASHRAE Transactions %D 1997 %T Guidelines for Modeling Projecting Fenestration Products %A Dariush K. Arasteh %A Elizabeth U. Finlayson %A Dragan C. Curcija %A Jeff Baker %A Charlie Huizenga %X

Heat transfer patterns in projecting fenestration products (greenhouse windows, skylights, etc.) are different than those with typical planar window products. The projecting surfaces often radiate to each other, thereby invalidating the commonly used assumption that fenestration product interior surfaces radiate to a uniform room air temperature. The convective portion of the surface heat transfer coefficient is also significantly different from the one used with planar geometries, and is even more dependent on geometry and location. Projecting fenestration product profiles must therefore be modeled in their entirety. This paper presents the results of complete cross section, variable film-coefficient, 2-D heat transfer modeling of two greenhouse windows using the next generation of window specific heat transfer modeling tools. The use of variable film-coefficient models is shown to increase the accuracy with which simulation tools can compute U-factors. Simulated U-factors are also determined using conventional constant film coefficient algorithms. The results from both sets of simulations are compared with measured values.

%B ASHRAE Transactions %C San Francisco, CA %V 104, Part 1 %8 01/1998 %G eng %1

Windows and Daylighting Group

%2 LBNL-40707 %0 Journal Article %J ASHRAE Transactions %D 1997 %T Improving Computer Simulations of Heat Transfer for Projecting Fenestration products: Using Radiation View-Factor Models %A Brent T. Griffith %A Dragan C. Curcija %A Daniel Turler %A Dariush K. Arasteh %X

The window well formed by the concave surface on the warm side of skylights and garden windows can cause surface heat-flow rates to be different for these projecting types of fenestration products than for normal planar windows. Current methods of simulating fenestration thermal conductance (U-value) use constant boundary condition values for overall surface heat transfer. Simulations that account for local variations in surface heat transfer rates (radiation and convection) may be more accurate for rating and labeling window products whose surfaces project outside a building envelope. This paper, which presents simulation and experimental results for one projecting geometry, is the first step in documenting the importance of these local effects.

A generic specimen, called the foam garden window, was used in simulations and experiments to investigate heat transfer of projecting surfaces. Experiments focused on a vertical cross section (measurement plane) located at the middle of the window well on the warm side of the specimen. The specimen was placed between laboratory thermal chambers that were operated at American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) winter heating design conditions. Infrared thermography was used to map surface temperatures. Air temperature and velocity were mapped throughout the measurement plane using a mechanical traversing system. Finite-element computer simulations that directly modeled element-to-element radiation were better able to match experimental data than simulations that used fixed coefficients for total surface heat transfer. Air conditions observed in the window well suggest that localized convective effects were the reason for the difference between actual and modeled surface temperatures. U-value simulation results were 5 to 10% lower when radiation was modeled directly.

%B ASHRAE Transactions %V 104, Part 1 %G eng %1

Windows and Daylighting Group

%2 LBNL-40706 %0 Report %D 1997 %T RESFEN 3.0: A PC Program for Calculating the Heating and Cooling Energy Use of Windows in Residential Buildings %A Yu Joe Huang %A Robert Sullivan %A Dariush K. Arasteh %A Robin Mitchell %X

Today's energy-efficient windows can dramatically lower the heating and cooling costs associated with windows while increasing occupant comfort and minimizing window surface condensation problems. However, consumers are often confused about how to pick the most efficient window for their residence. They are typically given window properties such as U-factors or R-values, Solar Heat Gain Coefficients or Shading Coefficients, and air leakage rates. However, the relative importance of these properties depends on the site and building specific conditions. Furthermore, these properties are based on static evaluation conditions that are very different from the real situation the window will be used in. Knowing the energy and associated cost implications of different windows will help consumers and builders make the best decision for their particular application, whether it is a new home, an addition, or a window replacement.

A computer tool such as RESFEN can help consumers and builders pick the most energy-efficient and cost-effective window for a given application. It calculates the heating and cooling energy use and associated costs as well as the peak heating and cooling demand for specific window products. Users define a problem by specifying the house type (single story or two story), geographic location, orientation, electricity and gas cost, and building configuration details (such as wall type, floor type, and HVAC systems). Window options are defined by specifying the window`s size, shading, and thermal properties: U-factor, Solar Heat Gain Coefficient, and air leakage rate. RESFEN calculates the energy and cost implications of the windows compared to insulated walls. The relative energy and cost impacts of two different windows can be compared against each other.

RESFEN 3.0 is a major improvement over previous versions of RESFEN because it performs hourly calculations using a version of the DOE 2.1E energy analysis simulation program.

%I Lawrence Berkeley National Laboratory %P 38 %8 12/1997 %2 LBNL-40682 %0 Journal Article %J ASHRAE Transactions %D 1997 %T The Significance of Bolts in the Thermal Performance of Curtain-Wall Frames for Glazed Façades %A Brent T. Griffith %A Elizabeth U. Finlayson %A Mehry Yazdanian %A Dariush K. Arasteh %X

Curtain walls are assemblies of glazings and metal frames that commonly form the exterior glass façades of commercial buildings. Evaluating the thermal performance of the bolts that hold curtain wall glazings in place is necessary to accurately rate the overall thermal performance of curtain walls. Using laboratory tests and computer simulations, we assessed the thermal performance of several different configurations of bolts and glazings. Curtain-wall samples were tested in the infrared thermography laboratory at the Lawrence Berkeley National Laboratory (LBNL) in Berkeley, California. Experimental results were compared to two-dimensional simulations approximating the thermal effect of the bolts using the parallel path and the isothermal planes calculation methods. We conclude that stainless steel bolts minimally affect curtain-wall thermal performance (approximately 18%) when spaced at least nine inches apart, which is the industry standard. Performance is increasingly compromised when there is less than nine inches between bolts or when steel bolts are used. We also show that the isothermal planes method of approximating curtain wall thermal performance can be used with 2-D heat transfer software typical of that used in the window industry to give conservative results for the thermal bridging effect caused by bolts.

%B ASHRAE Transactions %C San Francisco, CA %V 104, Part 1 %8 01/1998 %G eng %L LBNL-40690 %1

Windows and Daylighting Group

%2 LBNL-40690 %0 Conference Paper %B ASHRAE 1996 Summer Meeting, June 22-26, 1996 %D 1996 %T Energy Performance of Evacuated Glazings in Residential Buildings %A Robert Sullivan %A Fredric A. Beck %A Dariush K. Arasteh %A Stephen E. Selkowitz %X

This paper presents the results of a study investigating the energy performance of evacuated glazings or glazings which maintain a vacuum between two panes of glass. Their performance is measured by comparing results to prototype highly insulated superwindows as well as a more conventional insulating glass unit with a low-E coating and argon gas fill. We used the DOE-2.1E energy analysis simulation program to analyze the annual and hourly heating energy use due to the windows of a prototypical single-story house located in Madison, Wisconsin. Cooling energy performance was also investigated. Our results show that for highly insulating windows, the solar heat gain coefficient is as important as the windows U-factor in determining heating performance for window orientations facing west-south-east. For other orientations in which there is not much direct solar radiation, the windows U-factor primarily governs performance. The vacuum glazings had lower heating requirements than the superwindows for most window orientations. The conventional low-E window outperformed the superwindows for southwest-south-southeast orientations. These performance differences are directly related to the solar heat gain coefficients of the various windows analyzed. The cooling performance of the windows was inversely related to the heating performance. The low solar heat gain coefficients of the superwindows resulted in the best cooling performance. However, we were able to mitigate the cooling differences of the windows by using an interior shading device that reduced the amount of solar gain.

%B ASHRAE 1996 Summer Meeting, June 22-26, 1996 %C San Antonio, TX %V 102, Part 2 %8 06/1996 %G eng %1

Windows and Daylighting Group

%2 LBL-37130 %0 Conference Paper %B ACEEE 1996 Summer Study on Energy Efficiency in Buildings: Profiting from Energy Efficiency %D 1996 %T The National Energy Requirements of Residential Windows in the U.S.: Today and Tomorrow %A Karl J. Frost %A Joseph H. Eto %A Dariush K. Arasteh %A Mehry Yazdanian %X

This paper describes an end-use analysis of the national energy requirements of U.S. residential window technologies. We estimate that the current U.S. stock of 19 billion square feet of residential windows is responsible for 1.7 quadrillion BTUs (or quads) per year of energy use - 1.3 quads of heating and 0.4 quads of cooling energy - which represents about 2% of total U.S. energy consumption. We show that national energy use due to windows could be reduced by 25% by the year 2010 through accelerated adoption of currently available, advanced window technologies such as low-e and solar control low-e coatings, vinyl and wood frames, and superwindows. We evaluate the economics of the technologies regionally, considering both climatic and energy price variations, and find that the technologies would be cost effective for most consumers.

%B ACEEE 1996 Summer Study on Energy Efficiency in Buildings: Profiting from Energy Efficiency %C Pacific Grove, CA %8 08/1996 %G eng %U http://aceee.org/files/proceedings/1996/data/papers/SS96_Panel10_Paper07.pdf#page=1 %L LBNL-39692 %1

Windows and Daylighting Group

%2 LBNL-39692 %0 Conference Paper %B 1996 ACEEE Summer Study on Energy Efficiency in Buildings %D 1996 %T Transforming the Market for Residential Windows: Design Considerations for DOE's Efficient Window Collaborative %A Joseph H. Eto %A Dariush K. Arasteh %A Stephen E. Selkowitz %X

Market adoption of recent, commercially available technological advances that improve the energy performance of windows will lead to immediate economic and energy savings benefits to the nation. This paper is a scoping study intended to inform the design of a major DOE initiative to accelerate market adoption of these windows in the residential sector. We describe the structure of the U.S. residential window market and the interests of the various market players. We then briefly review five recent market transformation initiatives. Finally, we summarize our findings in a list of considerations we believe will be important for the DOE's initiative to transform the U.S. residential window market.

%B 1996 ACEEE Summer Study on Energy Efficiency in Buildings %I ACEEE %C Pacific Grove, CA %8 08/1996 %G eng %U http://aceee.org/files/proceedings/1996/data/papers/SS96_Panel10_Paper05.pdf#page=1 %L LBNL-42254 %1

Windows and Daylighting Group

%2 LBNL-42254 %0 Conference Paper %B Thermal Performance of the Exterior Envelopes of Buildings VI Conference %D 1995 %T Advances in Thermal and Optical Simulations of Fenestration Systems: The Development of WINDOW 5 %A Elizabeth U. Finlayson %A Dariush K. Arasteh %A Michael D. Rubin %A John Sadlier %A Robert Sullivan %A Charlie Huizenga %A Dragan C. Curcija %A Mark Beall %X

WINDOW is a personal-computer-based computer program used by manufacturers, researchers, and consumers to evaluate the thermal performance properties (U-factors, solar heat gain and shading coefficients, and visible transmittances) of complete windows and other fenestration systems. While WINDOW is used by thousands of users in the United States and internationally and is at the foundation of the National Fenestration Rating Council's U-factor and solar heat gain property procedures, improvements to the program are still necessary for it to meet user needs. Version 5, intended for release in late 1995, is being developed to meet these needs for increased accuracy, a flexible and state-of-the-art user interface, and the capabilities to handle more product types.

WINDOW 5 includes the capabilities to define and model the thermal performance of frames/dividers and their associated edge effects. Currently, such an analysis must be performed outside of WINDOW and requires simplifications to be made to frame profiles or is based on the use of generic frame and edge correlations. WINDOW's two-dimensional thermal model is composed of four sections: a graphical input, automatic grid generation, an finite-element analysis (FEA) solution, and the display of results. In the graphical input section, users are able to directly import a computer-aided design (CAD) drawing or a scanned image of a window profile, replicate its exact geometry, and assign material types and boundary conditions. The automatic grid generation is transparent to the user, with the exception of the requirement that complex shapes (i.e., an aluminum extrusion) be broken down into simpler polyshapes. Inclusion of an automatic grid generation makes detailed "true geometry" frame-and-edge heat-transfer analysis accessible to users without extensive knowledge of numerical methods of heat-transfer analysis. After the cross section is meshed it is sent to the FEA engine for solution and the results are returned. A postprocessor allows for the visual display of temperature and heat flux plots. Note that while this two-dimensional heat-transfer tool is being developed specifically for fenestration products, it also can be used to analyze other building envelope components.

WINDOW 5 also will include a built-in version of a national laboratory's program that allows the user to estimate the orientation-dependent annual energy impacts of a given window in a typical residence in various U.S. climates. This program is based on regressions to a database of DOE2.1 runs. Future versions will include a similar feature for commercial buildings.

Other technical additions include an improved angular/ spectral model for coated and uncoated glazings, the ability to analyze the optical properties of nonhomogeneous layers, and the ability to model the effects of laminated glazing layers. A door module permits the user to compute the total U-factors of exterior doors based on component U-factors calculated using the two-dimensional FEA module.

%B Thermal Performance of the Exterior Envelopes of Buildings VI Conference %C Clearwater Beach, FL %8 12/1995 %G eng %1

Windows and Daylighting Group

%2 LBL-37283 %0 Book Section %B Advances in Solar Energy, An Annual Review of Research and Development %D 1995 %T Advances in Window Technology: 1973-1993 %A Dariush K. Arasteh %X

Until the 1970s, the thermal performance of windows and other fenestration technologies was rarely of interest to manufacturers, designers, and scientists. Since then, however, a significant research and industry effort has focused on better understanding window thermal and optical behavior, how windows influence building energy patterns, and on the development of advanced products. This chapter explains how fenestration technologies can make a positive impact on building energy flows, what physical phenomena govern window heat and light transfer, what new products have been developed, and what new products are currently the subject of international research efforts.

%B Advances in Solar Energy, An Annual Review of Research and Development %P 339-382 %G eng %L LBL-36891 %1

Windows and Daylighting Group

%2 LBL-36891 %0 Conference Paper %B Thermal Performance of the Exterior Envelopes of Buildings VI Conference %D 1995 %T Edge Conduction in Vacuum Glazing %A Tom M. Simko %A Richard E. Collins %A Fredric A. Beck %A Dariush K. Arasteh %X

Vacuum glazing is a form of low-conductance double glazing using an internal vacuum between the two glass sheets to eliminate heat transport by gas conduction and convection. An array of small support pillars separates the sheets; fused solder glass forms the edge seal. Heat transfer through the glazing occurs by radiation across the vacuum gap, conduction through the support pillars, and conduction through the bonded edge seal. Edge conduction is problematic because it affects stresses in the edge region, leading to possible failure of the glazing; in addition, excessive heat transfer because of thermal bridging in the edge region can lower overall window thermal performance and decrease resistance to condensation.

Infrared thermography was used to analyze the thermal performance of prototype vacuum glazings, and, for comparison, atmospheric pressure superwindows. Research focused on mitigating the edge effects of vacuum glazings through the use of insulating trim, recessed edges, and framing materials. Experimentally validated finite-element and finite-difference modeling tools were used for thermal analysis of prototype vacuum glazing units and complete windows. Experimental measurements of edge conduction using infrared imaging were found to be in good agreement with finite-element modeling results for a given set of conditions. Finite-element modeling validates an analytic model developed for edge conduction.

%B Thermal Performance of the Exterior Envelopes of Buildings VI Conference %C Clearwater Beach, FL %8 03/1995 %G eng %1

Windows and Daylighting Group

%2 LBL-36958 %0 Conference Paper %B BETEC Fall Symposium, Superinsulations and the Building Envelope %D 1995 %T Gas Filled Panels: An Update on Applications in the Building Thermal Envelope %A Brent T. Griffith %A Dariush K. Arasteh %A Daniel Turler %X

This paper discusses the application of Gas-Filled Panels to the building thermal envelope. Gas-Filled Panels, or GFPs, are thermal insulating devices that retain a high concentration of a low-conductivity gas, at atmospheric pressure, within a multilayer infrared reflective baffle. The thermal performance of the panel depends on the type of gas fill and the baffle configuration. We present computer simulation results showing the improvement in thermal resistance resulting from using an argon-GFP in place of glass fiber batt insulation in wood-frame construction. This report also presents estimates of the quantity and cost of material components needed to manufacture GFPs using current prototype designs.

%B BETEC Fall Symposium, Superinsulations and the Building Envelope %C Washington, DC %8 11/1995 %G eng %L LBL-38093 %1

Windows and Daylighting Group

%2 LBL-38093 %0 Report %D 1995 %T An Infrared Thermography-Based Window Surface Temperature Database for the Validation of Computer Heat Transfer Models %A Fredric A. Beck %A Brent T. Griffith %A Daniel Turler %A Dariush K. Arasteh %X

Fenestration heat transfer simulation codes are used in energy performance rating and labeling procedures to model heat transfer through window systems and to calculate window U-values and condensation resistance factors. Experimental measurements of window thermal performance can direct the development of these codes, identify their strengths and weaknesses, set research priorities, and validate finished modeling tools. Infrared (IR) thermography is a measurement technique that is well suited to this task. IR thermography is a relatively fast, non-invasive, non-destructive technique that can resolve thermal performance differences between window components and window systems to a higher degree than a conventional hot box test. Infrared thermography provides spatial resolution of system performance by generating surface temperature maps of windows under controlled and characterized environmental conditions.

This paper summarizes basic theory and techniques for maximizing the accuracy and utility of infrared thermographic temperature measurements of window systems and components in a controlled laboratory setting. The physical setup of a complete infrared thermographic test facility at a major U.S. national research laboratory is described. Temperature measurement issues, and accuracy limits, for quantitative laboratory infrared thermography are discussed. An external reference emitter allows test-specific correction of absolute temperatures measured with an infrared scanner, resulting in 'an absolute measurement accuracy of ±O.5°C. Quantitative IR thermography is used to form a database of window surface temperature profiles for the validation of finite-element and finite-difference fenestration heat transfer modeling tools. An IR window surface temperature database with complete technical drawings of the windows tested; specification of all test window dimensions, materials, and thermal conductivities; environmental conditions of the tests with associated measurement errors; and two-dimensional surface temperature maps and selected cross sectional temperature profiles in a spreadsheet database format on an electronic media are presented.

%8 03/1995 %2 LBL-36957 Abs. %0 Conference Paper %B Thermal Performance of the Exterior Envelopes of Buildings VI Conference %D 1995 %T Issues Associated with the Use of Infrared Thermography for Experimental Testing of Insulated Systems %A Brent T. Griffith %A Fredric A. Beck %A Dariush K. Arasteh %A Daniel Turler %X

Infrared scanning radiometers are used to generate temperature maps of building envelope components, including windows and insulation. These temperature maps may assist in evaluating components thermal performance. Although infrared imaging has long been used for field evaluations, controlled laboratory conditions allow improvements in quantitative measurements of surface temperature using reference emitter techniques.

This paper discusses issues associated with the accuracy of using infrared scanning radiometers to generate temperature maps of building envelope components under steady-state, controlled laboratory conditions. Preliminary experimental data are presented for the accuracy and uniformity of response of one commercial infrared scanner. The specified accuracy of this scanner for temperature measurements is 2 °C or 2% of the total range of values (span) being measured. A technique is described for improving this accuracy using a temperature-controlled external reference emitter. Minimum temperature measurement accuracy with a reference emitter is estimated at ±0.5 °C for ambient air and background radiation at 21.1 °C and surface temperatures from 0 °C to 21 °C.

Infrared imaging, with a reference emitter technique, is being used to create a database of temperature maps for a range of window systems, varying in physical complexity, material properties, and thermal performance. The database is to be distributed to developers of fenestration heat transfer simulation programs to help validate their models. Representative data are included for two insulated glazing units with different spacer systems.

%B Thermal Performance of the Exterior Envelopes of Buildings VI Conference %C Clearwater Beach, FL %8 12/1995 %G eng %1

Windows and Daylighting Group

%2 LBL-36734 %0 Conference Paper %B Window Innovations Conference 1995 %D 1995 %T NFRC Efforts to Develop a Residential Fenestration Annual Energy Rating Methodology %A Brian Crooks %A James Larsen %A Robert Sullivan %A Dariush K. Arasteh %A Stephen E. Selkowitz %X

This paper documents efforts currently being undertaken by the National Fenestration Rating Councils Annual Energy Rating Subcommittee to develop procedures to quantify the energy impacts of fenestration products in typical residential buildings throughout the United States. Parallel paths focus on (1) the development of simplified heating and cooling indices and (2) the development of a more detailed methodology to calculate the cost and energy impacts of specific products in a variety of housing types. These procedures are currently under discussion by NFRCs Technical Committee; future efforts will also address commercial buildings.

%B Window Innovations Conference 1995 %C Toronto, Canada %8 06/1995 %G eng %1

Windows and Daylighting Group

%2 LBL-36896 %0 Conference Paper %B Window Innovations 95 %D 1995 %T Recent Technical Improvements to the WINDOW Computer Program %A Dariush K. Arasteh %A Elizabeth U. Finlayson %A Michael D. Rubin %A John Sadlier %X

The WINDOW series of computer programs has been used since 1985 to model the thermal and optical properties of windows. Each succeeding version of WINDOW has brought its user base new technical capabilities, improvements to the user interface, and greater accuracy. Technical improvements to the current version, which will be released as version 5, are at first being released as stand-alone programs. This paper summarizes the capabilities and algorithms of two of these programs, THERM and LAMINATE. A third stand alone program, RESFEN, which calculates the annual energy effects of specific windows in a typical house throughout the US, will also be incorporated into WINDOW 5; because this program is already in use and documented, it is not discussed in this paper. THERM allows the user to evaluate two dimensional (2-D) heat transfer effects through the solid elements of a window while LAMINATE determines the optical properties of an individual glazing layer with an applied film. Both of these programs are undergoing final development at the time of this writing and will be released as separate programs before they are incorporated into WINDOW 5.

%B Window Innovations 95 %C Toronto, Canada %8 06/1995 %G eng %L LBNL-41680 %1

Windows and Daylighting Group

%2 LBNL-41680 %0 Journal Article %J ASHRAE Transactions %D 1995 %T Surface Temperatures of Insulated Glazing Units: Infrared Thermography Laboratory Measurements %A Brent T. Griffith %A Daniel Turler %A Dariush K. Arasteh %X

Data are presented for the distribution of surface temperatures on the warm-side surface of seven different insulated glazing units. Surface temperatures are measured using infrared thermography and an external referencing technique. This technique allows detailed mapping of surface temperatures that is non-intrusive. The glazings were placed between warm and cold environmental chambers that were operated at conditions corresponding to standard design conditions for winter heating. The temperatures conditions are 21.1 °C (70 °F) and -17.8 °C (0 °F) on the warm and cold sides, respectively. Film coefficients varied somewhat with average conditions of about 7.6 W/m2 K (1.34 Btu/h ft2 °F) for the warm-side and 28.9 W/m2 K (5.1 Btu/h ft2 °F) for the cold-side. Surface temperature data are plotted for the vertical distribution along the centerline of the IG and for the horizontal distribution along the centerline. This paper is part of larger collaborative effort that studied the same set of glazings.

%B ASHRAE Transactions %V 102 %8 12/1995 %G eng %N 2 %1

Windows and Daylighting Group

%2 LBL-38117 %0 Conference Paper %B Windows Innovations Conference 95 %D 1995 %T Using Infrared Thermography for the Creation of a Window Surface Temperature Database to Validate Computer Heat Transfer Models %A Fredric A. Beck %A Brent T. Griffith %A Daniel Turler %A Dariush K. Arasteh %X

Infrared thermography is a non-invasive, non-destructive technique for measuring surface temperatures of an object. These surface temperatures can be used to understand the thermal performance of window components and complete window systems. Infrared (IR) thermography has long been used for qualitative field assessment of window thermal performance, and is now being used in the laboratory for quantitative assessments of window thermal performance. As windows become better and better, more refined test methods and/or simulation tools are required to accurately detect performance changes and make comparisons between products. While hot box calorimetery has worked well to characterize the thermal performance of conventional insulating products, differences in the thermal performance of new highly insulating systems are often less than the resolution of conventional hot box calorimeters. Infrared imaging techniques offer the opportunity to resolve small differences in the thermal performance of components of highly insulating window systems that hot box measurements are not able to identify.

Lawrence Berkeley Laboratory (LBL), a U.S. national research laboratory, is currently using infrared thermography to develop a database of measured surface temperature profiles for a number of different fenestration products for use in validating both basic and advanced two- and three-dimensional finite element method (FEM) and finite difference method (FDM) fenestration heat transfer simulation programs. IR surface temperature data, when taken under controlled laboratory conditions, can be used to direct the development of these simulation codes, identify their strengths and weaknesses, set research priorities, and validate finished modeling tools. Simulation of fenestration heat transfer is faster and less expensive than hot box testing of fenestration products, and forms the basis of window energy codes being implemented, developed, or considered in the US, Canada, the Former Soviet Union, Europe, and Australia. The National Fenestration Rating Council (U. S.) has developed a simulation-based standard which is used to rate and label window U-values for a published directory of over 10,000 different window products.

%B Windows Innovations Conference 95 %C Toronto, Canada %8 06/1995 %G eng %L LBL-36975 %1

Windows and Daylighting Group

%2 LBL-36975 %0 Conference Paper %B 19th National Passive Solar Conference %D 1994 %T Integrated Window Systems: An Advanced Energy-Efficient Residential Fenestration Product %A Dariush K. Arasteh %A Brent T. Griffith %A Paul LaBerge %X

The last several years have produced a wide variety of new window products aimed at reducing the energy impacts associated with residential windows. Improvements have focused on reducing the rate at which heat flows through the total window product by conduction/convection and thermal radiation (quantified by the U-factor) as well as in controlling solar heat gain (measured by the Solar Heat Gain Coefficient (SHGC) or Shading Coefficient (SC).

Significant improvements in window performance have been made with low-E coated glazings, gas fills in multiple pane windows and with changes in spacer and frame materials and designs. These improvements have been changes to existing design concepts. They have pushed the limits of the individual features and revealed weaknesses. The next generation of windows will have to incorporate new materials and ideas, like recessed night insulation, seasonal sun shades and structural window frames, into the design, manufacturing and construction process, to produce an integrated window system that will be an energy and comfort asset.

%B 19th National Passive Solar Conference %C San Jose, CA %8 06/1994 %G eng %L LBL-35417 %1

Windows and Daylighting Group

%2 LBL-35417 %0 Conference Paper %B Thermal Performance of the Exterior Envelopes of Buildings V Conference %D 1994 %T Modeling Windows in DOE 2.1E %A M. Susan Reilly %A Frederick C. Winkelmann %A Dariush K. Arasteh %A William L. Carroll %X

The most recent version of the DOE-2 building energy simulation program, DOE-2.1E, provides for more detailed modeling of the thermal and optical properties of windows. The window calculations account for the temperature effects on U-value, and update the incident angle correlations for the solar heat gain properties and visible transmittance. Initial studies show up to a 30% difference in calculating peak solar heat gain between the detailed approach and a constant shading-coefficient approach. The modeling approach is adapted from Lawrence Berkeley Laboratorys WINDOW 4 computer program, which is used in the National Fenestration Rating Council (NFRC) U-value rating procedure 100-91. This gives DOE-2.1E the capability to assess the annual and peak energy performance of windows consistent with the NFRC procedure. The program has an extensive window library and algorithms for simulating switchable glazings. The program also accounts for the influence of framing elements on the heat transfer and solar heat gain through the window.

%B Thermal Performance of the Exterior Envelopes of Buildings V Conference %C Clearwater Beach, FL %8 12/1992 %G eng %L LBL-33192 %1

Windows and Daylighting Group

%2 LBL-33192 %0 Journal Article %J ASHRAE Transactions %D 1994 %T Spectrally Selective Glazings for Residential Retrofits in Cooling-Dominated Climates %A Eleanor S. Lee %A Deborah Hopkins %A Michael D. Rubin %A Dariush K. Arasteh %A Stephen E. Selkowitz %K deserts %K domestic %K energy conservation %K Glazing %K housing %K modernising %K subtropics %K usa %K windows %X

Spectrally selective glazings can substantially reduce energy consumption and peak demand in residences by significantly reducing solar gains with minimal loss of illumination and view. In cooling-dominated climates, solar gains contribute 24–31% to electricity consumption and 40–43% to peak demand in homes with single pane clear glazing—standard practice for residential construction built before the implementation of building energy efficiency standards. The existing residential housing stock therefore offers a prime opportunity for significant demand-side management (DSM),but the energy and cost savings must be weighed against retrofit first costs in order for the technology to achieve full market penetration. Using DOE-2.1D for numerical simulation of building energy performance, we quantify the energy and peak demand reductions, cost savings, and HVAC capacity reductions using spectrally selective glazings for five cooling-dominated climates in California. The cost-effectiveness of various material and installation retrofit options is discussed. Glazing material improvements for retrofit applications that are needed to achieve a prescribed cost savings are also given.

%B ASHRAE Transactions %V 100 %G eng %N 1 %1

Windows and Daylighting Group

%2 LBL-34455 %! ASHRAE Trans. %0 Report %D 1994 %T WINDOW 4.1: Program Description %A Dariush K. Arasteh %A Elizabeth U. Finlayson %A Charlie Huizenga %X

WINDOW 4.1 is a publicly available IBM PC compatible computer program developed by the Windows and Daylighting Group at Lawrence Berkeley Laboratory for calculating total window thermal performance indices (i.e. U-values, solar heat gain coefficients, shading coefficients, and visible transmittances). WINDOW 4.1 provides a versatile heat transfer analysis method consistent with the rating procedure developed by the National Fenestration Rating Council (NFRC). The program can be used to design and develop new products, to rate and compare performance characteristics of all types of window products, to assist educators in teaching heat transfer through windows, and to help public officials in developing building energy codes.

WINDOW 4.1 is an update to WINDOW 4.0. The WINDOW 4 series is a major revision to previous versions of WINDOW. We strongly urge all users to read this manual before using the program. Users who need professional assistance with the WINDOW 4.1 program or other window performance simulation issues are encouraged to contact one or more of the NFRC-accredited Simulation Laboratories.

%G eng %L LBL-35298 %1

Windows and Daylighting Group

%2 LBL-35298 %0 Conference Paper %B 22nd International Thermal Conductivity Conference %D 1993 %T Optimizing the Effective Conductivity and Cost of Gas-Filled Panel Thermal Insulations %A Brent T. Griffith %A Daniel Turler %A Dariush K. Arasteh %X

Gas-Filled Panels, or GFPs, are an advanced theimal insulation that employ a low-conductivity, inert gas, at atmospheiic pressure, within a multilayer reflective baffle. The thermal performance of GFPs varies with gas conductivity, overall panel thickness, and baffle construction. Design parameters of baffle constructions that have a strong effect on GFP thermal resistance are (1) cavities per thickness, (2) cavity surface emittance, and (3) conductance of the baffle materials. GFP thermal performances, where the above parameters were varied, were modeled on a spreadsheet by iterative calculation of one-dimensional energy balances. Heat flow meter apparatus measurements of prototype GFP effective conductivities have been made and are compared to results of the calculations. The costs associated with varying baffle constructions are estimated based on the prices of commercial material components. Results are presented in terms of cost per area per unit thermal resistance ($/Area*R-Value) and are usefid for optimizing GFP designs forsair, argon, or krypton gas fills and a desired effective conductivity and thickness.

%B 22nd International Thermal Conductivity Conference %C Tempe, AZ %8 11/1993 %G eng %L LBL-36134 %1

Windows and Daylighting Group

%2 LBL-36134 %0 Journal Article %J ASHRAE Transactions %D 1993 %T Phase I Results of the NFRC U-Value Procedure Validation Project %A Dariush K. Arasteh %A Fredric A. Beck %A Nehemiah Stone %A William DuPont %A R. Christophe Mathis %A Michael Koenig %X

The NFRC U-Value Procedure Validation Project was undertaken by a collaborative group of industry, public utility, trade associations, and government researchers in order to validate the testing and calculational methods of the NFRC 100-91: Procedure for Determining Fenestration Product Thermal Properties (Currently Limited to U-Values). This paper summarizes the validation projects goals and test methodology, the results of the data analysis, and the recommendations following completion of Phase I of the project. Simulations performed according to NFRC 100-91 are shown to agree with each other, to within the NFRC tolerance, in 100% of the cases. Window test results with perpendicular wind performed according to NFRC 100-91 are shown to agree with each other, to within the NFRC tolerance, in 84% of the cases. Simulations and perpendicular wind window test results are shown to agree with each other, to within the NFRC tolerance, in 80% of the cases. Testing of skylights was shown to be problematic under the procedure as written at the time. Agreement between tests and simulations will improve as a result of a strong NFRC education and accreditation program.

%B ASHRAE Transactions %V 100, Pt. 1 %8 08/1993 %G eng %1

Windows and Daylighting Group

%2 LBL-34270 %0 Report %D 1993 %T Savings from Energy Efficient Windows: Current and Future Savings from New Fenestration Technologies in the Residential Market %A Karl J. Frost %A Dariush K. Arasteh %A Joseph H. Eto %X

Heating and cooling energy lost through windows in the residential sector (estimated at two-thirds of the energy lost through windows in all sectors) currently accounts for 3 percent (or 2.8 quads) of total US energy use, costing over $26 billion annually in energy bills. Installation of energy-efficient windows is acting to reduce the amount of energy lost per unit window area. Installation of more energy efficient windows since 1970 has resulted in an annual savings of approximately 0.6 quads. If all windows utilized existing cost effective energy conserving technologies, then residential window energy losses would amount to less than 0.8 quads, directly saving $18 billion per year in avoided energy costs. The nationwide installation of windows that are now being developed could actually turn this energy loss into a net energy gain. Considering only natural replacement of windows and new construction, appropriate fenestration policies could help realize this potential by reducing annual residential window energy losses to 2.2 quads by the year 2012, despite a growing housing stock.

%G eng %L LBNL-33956 %1

Windows and Daylighting Group

%2 LBL-33956 %0 Journal Article %J ASHRAE Transactions %D 1993 %T A Validation of the WINDOW4/FRAME3 Linear Interpolation Methodology %A Fredric A. Beck %A Dariush K. Arasteh %X

The validity of a method to reduce the total number of computer simulations which must be run to determine the U-values of a window product line with multiple glazing options is examined. The accuracy and limits of this method, which uses the WINDOW4 and FRAME simulation programs, is evaluated by comparing the edge, frame, and total window U-values calculated on the basis of single point FRAME simulations to those U-values as calculated on the basis of four point FRAME simulations combined with linear interpolation of frame and edge U-values by WINDOW4. The accuracy of this procedure is examined for two frame types, a low thermal conductivity wood-framed casement and a high thermal conductivity aluminum-framed casement, using both aluminum spacers and insulating spacers over a wide range of glazing types. The effect of center-of-glass U-value, overall glazing thickness and spacer type on frame and edge-of-glass U-values is discussed. It is shown that the agreement between total window U-values as calculated by the single point and four point simulation methods is better than 1% for double and triple-glazed windows with aluminum spacers, better than 1% for double-glazed windows with insulating spacers, and better than 2% for triple-glazed windows with insulating spacers.

%B ASHRAE Transactions %V 100, Part 1 %G eng %L LBL-34271 %1

Windows and Daylighting Group

%2 LBL-34271 %0 Report %D 1993 %T Window 4.0: Documentation of Calculation Procedures %A Elizabeth U. Finlayson %A Dariush K. Arasteh %A Charlie Huizenga %A Michael D. Rubin %A M. Susan Reilly %X

WINDOW 4.0 is a publicly available IBM PC compatible computer program developed by the Building Technologies Group at the Lawrence Berkeley Laboratory for calculating the thermal and optical properties necessary for heat transfer analyses of fenestration products. This report explains the calculation methods used in WINDOW 4.0 and is meant as a tool for those interested in understanding the procedures contained in WINDOW 4.0. All the calculations are discussed in the International System of units (SI).

%G eng %L LBL-33943 %1

Windows and Daylighting Group

%2 LBL-33943 %0 Report %D 1993 %T Window U-Value Effects on Residential Cooling Load %A Robert Sullivan %A Karl J. Frost %A Dariush K. Arasteh %A Stephen E. Selkowitz %X

This paper presents the results of a study investigating the effects of window U-value changes on residential cooling loads. We used the DOE-2.1D energy analysis simulation program to analyze the hourly, daily, monthly, and annual cooling loads as a function of window U-value. The performance of a prototypical single-story house was examined in three locations: hot and humid, Miami FL; hot and dry, Phoenix AZ; and a heating-dominated location with a mildly hot and humid summer, Madison WI. Our results show that when comparing windows with identical orientation, size, and shading coefficient, higher U-value windows often yield lower annual cooling loads, but lower U-value windows yield lower peak cooling loads. This occurs because the window with the higher U-value conducts more heat from inside the residence to the outside during morning and evening hours when the outside air temperature is often lower than the inside air temperature; and, a lower U-value window conducts less heat from outside to inside during summer afternoon peak cooling hours. The absolute effects are relatively small when compared to total annual cooling which is typically dominated by window solar heat gain effects, latent loads, and internal loads. The U-value effect on cooling is also small when compared to both the effects of U-value and solar heat gain on heating load. Our modeling assumed that U-value and solar heat gain could be independently controlled. In fact, reducing window conductance to the levels used in this study implies adding a second glazing layer which always reduces solar heat gain, thus reducing annual cooling. Thus, when we compare realistic options, e.g., single pane clear to double pane clear, or single pane tinted to double pane tinted, the double pane unit shows lower annual cooling, as well as lower peak loads.

%G eng %L LBL-34648 %1

Windows and Daylighting Group

%2 LBL-34648 %0 Report %D 1985 %T The Effects of Skylight Parameters on Daylighting Energy Savings %A Dariush K. Arasteh %A Russell Johnson %A Stephen E. Selkowitz %X

Skylight parameters that affect lighting, cooling, heating, fan, and total energy use in office buildings are examined using the state-of-the-art building energy analysis computer code, DOE-2.1B. The lighting effects of skylight spatial distribution, skylight area, skylight visible transmission, well factor, illumination setpoint, interior partitions, ceiling height, and glazing characteristics are discussed. This study serves as the foundation for the creation of a DOE-2.1B database and design tools for estimating daylighting energy savings from skylights.

%G eng %L LBL-17456 %1

Windows and Daylighting Group

%2 LBL-17456 %0 Journal Article %J ASHRAE Transactions %D 1985 %T Energy Performance and Savings Potentials with Skylights %A Dariush K. Arasteh %A Russell Johnson %A Stephen E. Selkowitz %A Robert Sullivan %X

This study systematically explores the energy effects of skylight systems in a prototypical office building module and examines the savings from daylighting. For specific climates, roof/skylight characteristics are identified that minimize total energy or peak electrical demand. Simplified techniques for energy performance calculation are also presented based on a multiple regression analysis of our data base so that one may easily evaluate daylightings effects on total and component energy loads and electrical peaks. This provides additional insights into the influence of skylight parameters on energy consumption and electrical peaks. We use the DOE-2.15 energy analysis program with newly incorporated daylighting algorithms to determine hourly, monthly, and annual impacts of daylighting strategies on electrical lighting consumption, cooling, heating, fan power, peak electrical demands, and total energy use. A database of more than 2000 parametric simulations for 14 U.S. climates has been generated. Parameters varied include skylight-to-roof ratio, shading coefficient, visible transmittance, skylight well light loss, electric lighting power density, roof heat transfer coefficient, and electric lighting control type.

%B ASHRAE Transactions %V 91 %P 154-179 %G eng %L LBL-17457 %1

Windows and Daylighting Group

%2 LBL-17457 %0 Conference Paper %B Windows in Building Design and Maintanence %D 1984 %T Skylight Energy Performance and Design Optimization %A Dariush K. Arasteh %A Russell Johnson %A Robert Sullivan %X

Proper skylight utilization can significantly lower energy requirements and peak electrical loads for space conditioning and lighting in commercial buildings. In this study we systematically explore the energy effects of skylight systems in a prototypical officesbuilding and examine the savings from daylighting. We used the DOE-2.1B energy analysis computer program with its newly incorporated daylighting algorithims to generate more than 2000 parametric simulations for seven U.S. climates. The parameters varied include skylight-to-roof ratio, shading coefficient, visible transmittance, skylight well light loss, electric lighting powersdensity, roof heat transfer coefficient, and type of electric lighting control. For specific climates we identify roof/skylight characteristics that minimize total energy or peak electrical load requirements.

%B Windows in Building Design and Maintanence %C Gothenburg, Sweden %8 06/1984 %G eng %L LBL-17476 %1

Windows and Daylighting Group

%2 LBL-17476