@article {57039, title = {An empirical study of a full-scale polymer thermochromic window and its implications on material science development objectives}, journal = {Solar Energy Materials and Solar Cells}, volume = {116}, year = {2013}, month = {09/2013}, pages = {14-26}, chapter = {14}, abstract = {

Large-area polymer thermochromic (TC) laminated windows were evaluated in a full-scale testbed office. The TC interlayer film exhibited thermochromism through a ligand exchange process, producing a change in solar absorption primarily in the visible range while maintaining transparent, undistorted views through the material. The film had a broad switching temperature range and when combined to make an insulating window unit had center-of-glass properties of Tsol=0.12-0.03, Tvis=0.28-0.03 for a glass temperature range of 24-75{\textdegree}C. Field test measurements enabled characterization of switching as a function of incident solar irradiance and outdoor air temperature, illustrating how radiation influences glass temperature and thus effectively lowers the critical switching temperature of TC devices. This was further supported by EnergyPlus building energy simulations. Both empirical and simulation data were used to illustrate how the ideal critical switching temperature or temperature range for TC devices should be based on zone heat balance, not ambient air temperature. Annual energy use data are given to illustrate the energy savings potential of this type of thermochromic. Based on observations in the field,a broad switching temperature range was found to be useful in ensuring a uniform appearance when incident irradiance is non-uniform across the facade. As indicated in prior research, a high visible transmittance in both the switched and unswitched state is also desirable to enable reduction of lighting energy use and enhance indoor environmental quality.

}, keywords = {buildings energy efficiency, Solar control, Thermochromic, windows}, doi = {10.1016/j.solmat.2013.03.043}, author = {Eleanor S. Lee and Xiufeng Pang and Sabine Hoffmann and Howdy Goudey and Anothai Thanachareonkit} } @article {58230, title = {Near-Infrared Spectrally Selective Plasmonic Electrochromic Thin Films}, journal = {Advanced Optical Materials}, volume = {1}, year = {2013}, month = {03/2013}, pages = {215 - 220}, abstract = {

A plasmonic electrochromic effect in which electrochemical doping reversibly modulates near-infrared surface plasmon absorption of aluminium-doped zinc oxide and tin-doped indium oxide nanocrystals is reported. Optical performance, switching kinetics, and cycling durability point to high-performance NIR selective plasmonic electrochromic coatings based on earth-abundant materials.

}, keywords = {aluminum zinc oxide, indium tin oxide, nanocrystal, spectroelectrochemistry, surface plasmon}, doi = {10.1002/adom.201200051}, author = {Guillermo Garcia and Raffaella Buonsanti and Anna Llordes and Evan L. Runnerstrom and Amy Bergerud and Delia J. Milliron} } @techreport {60935, title = {A Pilot Demonstration of Electrochromic and Thermochromic Windows in the Denver Federal Center, Building 41, Denver, Colorado}, year = {2013}, note = {

Completed September 30, 2012, released March 30, 2014.

}, month = {07/2013}, abstract = {

Chromogenic glazing materials are emerging technologies that tint reversibly from a clear to dark tinted state either passively in response to environmental conditions or actively in response to a command from a switch or building automation system. Switchable coatings on glass manage solar radiation and visible light while enabling unobstructed views to the outdoors. Building energy simulations estimate that actively controlled, near-term chromogenic glazings can reduce perimeter zone heating, ventilation, and air- conditioning (HVAC) and lighting energy use by 10-20\% and reduce peak electricity demand by 20-30\%, achieving energy use levels that are lower than an opaque, insulated wall.

This project demonstrates the use of two types of chromogenic windows: thermochromic and electrochromic windows. By 2013, these windows will begin production in the U.S. by multiple vendors at high-volume manufacturing plants, enabling lower cost and larger area window products to be specified. Both technologies are in the late R\&D stage of development, where cost reductions and performance improvements are underway. Electrochromic windows have been installed in numerous buildings over the past four years, but monitored energy-efficiency performance has been independently evaluated in very limited applications. Thermochromic windows have been installed in one other building with an independent evaluation, but results have not yet been made public.

}, keywords = {building controls, daylighting, Demand Side Management, electrochromic, energy-efficiency, Smart windows, switchable windows, Thermochromic, Window}, url = {http://gsa.gov/portal/content/187967}, author = {Eleanor S. Lee and Luis L. Fernandes and Howdy Goudey and Jacob C. Jonsson and Dragan C. Curcija and Xiufeng Pang and Dennis L. DiBartolomeo and Sabine Hoffmann} } @article {58229, title = {Regional performance targets for transparent near-infrared switching electrochromic window glazings}, journal = {Building and Environment}, volume = {61}, year = {2013}, month = {03/2013}, pages = {160 - 168}, abstract = {

With building heating and cooling accounting for nearly 14\% of the national energy consumption, emerging technologies that improve building envelope performance have significant potential to reduce building energy consumption. Actual savings from these technologies will depend heavily upon their performance in diverse climate and operational conditions. In many cases, early-stage research can benefit from detailed investigation in order to develop performance thresholds and identify target markets. One example, a dynamic, highly transparent, near-infrared switching electrochromic (NEC) window glazing, is the focus of this investigation. Like conventional electrochromics, the NEC glazing can dynamically tune its optical properties with a small applied voltage. Consequently, the glazing can block or transmit solar heat to reduce cooling or heating loads, respectively. Unlike conventional electrochromics, NEC glazings remain transparent to visible light, causing no adverse effect to daylighting or building aesthetics. This study utilizes the software COMFEN to simulate a broad range of NEC performance levels, for commercial and residential buildings in 16 climate-representative reference cities. These simulations are the basis for identifying performance levels necessary to compete with existing static technologies. These results indicate that energy savings are strongly influenced by blocking-state performance. Additionally, residential applications have lower performance requirements due to their characteristic internal heat gains. Finally, the most dynamic NEC performance level is simulated in competition with high performing static alternatives. Here heating and cooling energy savings range from 5 to 11\ kWh/m2 yr for commercial and 8{\textendash}15\ kWh/m2 yr for residential, in many regions on the order of 10\%.

}, keywords = {Dynamic windows, Electrochromic glazings, NIR-switching, Performance targets, Solar heat gain}, issn = {03601323}, doi = {10.1016/j.buildenv.2012.12.004}, author = {Nicholas DeForest and Arman Shehabi and Guillermo Garcia and Jeffery B. Greenblatt and Eric R. Masanet and Eleanor S. Lee and Stephen E. Selkowitz and Delia J. Milliron} } @article {57807, title = {U.S. energy savings potential from dynamic daylighting control glazings}, journal = {Energy and Buildings}, volume = {66}, year = {2013}, month = {11/2013}, pages = {415-423}, chapter = {415}, abstract = {

Daylighting controls have the potential to reduce the substantial amount of electricity consumed for lighting in commercial buildings. Material science research is now pursuing the development of a dynamic prismatic optical element (dPOE) window coating that can continuously readjust incoming light to maximize the performance and energy savings available from daylighting controls. This study estimates the technical potential for energy savings available from vertical daylighting strategies and explores additional savings that may be available if current dPOE research culminates in a successful market-ready product. Radiance daylight simulations are conducted with a multi-shape prismatic window coating. Simulated lighting energy savings are then applied to perimeter floorspace estimates generated from U.S. commercial building stock data. Results indicate that fully functional dPOE coatings, when paired with conventional vertical daylight strategies, have the potential to reduce energy use associated with U.S. commercial electric lighting demand by as much as 930 TBtu. This reduction in electric lighting demand represents an approximately 85\% increase in the energy savings estimated from implementing conventional vertical daylight strategies alone. Results presented in this study provide insight into energy and cost performance targets for dPOE coatings, which can help accelerate the development process and establish a successful new daylighting technology.

}, keywords = {Clerestories, daylighting, Dynamic prismatic optical elements (dPOE), energy efficiency, Glare, indoor environmental quality, radiance, windows}, doi = {10.1016/j.enbuild.2013.07.013}, author = {Arman Shehabi and Nicholas DeForest and Andrew McNeil and Eric R. Masanet and Jeffery B. Greenblatt and Eleanor S. Lee and Georgeta Masson and Brett A. Helms and Delia J. Milliron} } @article {11869, title = {Fenestration of Today and Tomorrow: A State-of-the-Art Review and Future Research Opportunities}, journal = {Solar Energy Materials and Solar Cells}, volume = {96}, number = {2012}, year = {2012}, month = {01/2012}, pages = {1-28}, chapter = {1}, abstract = {

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.

}, keywords = {Fenestration, Low-e, Multilayer glazing, Smart window, Solar cell glazing, Vacuum glazing}, doi = {10.1016/j.solmat.2011.08.010}, author = {Bj{\o}rn Petter Jelle and Andrew Hynd and Arlid Gustavsen and Dariush K. Arasteh and Howdy Goudey and Robert Hart} } @article {58919, title = {Dynamically Modulating the Surface Plasmon Resonance of Doped Semiconductor Nanocrystals}, journal = {Nano Letters}, volume = {11}, year = {2011}, month = {10/2011}, pages = {4415 - 4420}, abstract = {

Localized surface plasmon absorption features arise at high doping levels in semiconductor nanocrystals, appearing in the near-infrared range. Here we show that the surface plasmons of tin-doped indium oxide nanocrystal films can be dynamically and reversibly tuned by postsynthetic electrochemical modulation of the electron concentration. Without ion intercalation and the associated material degradation, we induce a \> 1200 nm shift in the plasmon wavelength and a factor of nearly three change in the carrier density.

}, keywords = {doping, indium tin oxide, nanocrystal, spectroelectrochemistry, surface plasmon}, issn = {1530-6984}, doi = {10.1021/nl202597n}, author = {Guillermo Garcia and Raffaella Buonsanti and Evan L. Runnerstrom and Rueben J. Mendelsberg and Anna Llordes and Andr{\'e} Anders and Thomas J. Richardson and Delia J. Milliron} } @article {12005, title = {Key Elements of and Materials Performance Targets for Highly Insulating Window Frames}, journal = {Energy and Buildings}, volume = {43}, number = {10}, year = {2011}, month = {10/2011}, pages = {2583-2594}, chapter = {2583}, abstract = {

The thermal performance of windows is important for energy efficient buildings. Windows typically account for about 30{\textendash}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{\textendash}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.

}, keywords = {Fenestration, heat transfer modeling, thermal performance, thermal transmittance, u-factor, window frames}, doi = {10.1016/j.enbuild.2011.05.010}, author = {Arlid Gustavsen and Steinar Grynning and Dariush K. Arasteh and Bj{\o}rn Petter Jelle and Howdy Goudey} } @techreport {1218, title = {Using Helmholtz reciprocity in variable resolution BSDFs in Radiance}, year = {2011}, month = {11/2011}, institution = {Bartenbach L-chtLabor}, author = {David Geisler-Moroder} } @techreport {1219, title = {Validation of variable resolution BSDFs in Radiance}, year = {2011}, month = {11/2011}, institution = {Bartenbach L-chtLabor}, abstract = {

In this document results of the validation of the "Variable Resolution BSDF" approach as presented at the 10th International Radiance Workshop (G.Ward, A.McNeil, "A Variable-resolution BSDF Implementation") are presented.

Variable-resolution BSDFs are generated with genBSDF for the RADIANCE native materials plastic, trans, and glass (isotropic) and plastic2 and trans2 (anisotropic). Both, the maximum resolution (1024 x 1024 patches or 4096 x 4096 patches) as well as the number of specular samples (16 or 64) are varied.

The resulting data is reduced with rttree_reduce at various degrees (0\%, i.e. no reduction, 95\%, i.e. reduction by approximately 95\%, and 99\%, i.e. only about 1\% of data left).

}, author = {David Geisler-Moroder} } @conference {1408, title = {Experimental and Numerical Examination of the Thermal Transmittance of High Performance Window Frames}, booktitle = {Thermal Performance of the Exterior Envelopes of Whole Buildings XI International Conference, December 5-9, 2010}, year = {2010}, month = {09/2010}, address = {Clearwater Beach, FL}, abstract = {

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.

}, keywords = {experimental, Fenestration, frame cavity, heat transfer modeling, hot box, international standards, thermal transmittance, U-value, window frames}, author = {Arlid Gustavsen and Goce Talev and Dariush K. Arasteh and Howdy Goudey and Christian Kohler and Sivert Uvsl{\o}kk and Bj{\o}rn Petter Jelle} } @techreport {1631, title = {Modeling Windows in Energy Plus with Simple Performance Indices}, year = {2009}, month = {10/2009}, abstract = {

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.

}, author = {Dariush K. Arasteh and Christian Kohler and Brent T. Griffith} } @article {11733, title = {Developing Low-Conductance Window Frames: Capabilities and Limitations of Current Window Heat Transfer Design Tools}, journal = {Journal of Building Physics}, volume = {32}, number = {2}, year = {2008}, pages = {131-153}, abstract = {

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.
}, author = {Arlid Gustavsen and Dariush K. Arasteh and Bj{\o}rn Petter Jelle and Dragan C. Curcija and Christian Kohler} } @conference {11927, title = {Highly Insulating Glazing Systems using Non-Structural Center Glazing Layers}, booktitle = {2008 Annual ASHRAE Meeting}, year = {2008}, month = {06/2008}, address = {Salt Lake City, UT}, abstract = {

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-{\textdegree}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.

}, author = {Dariush K. Arasteh and Howdy Goudey and Christian Kohler} } @techreport {1846, title = {State-of-the-Art Highly Insulating Window Frames - Research and Market Review}, number = {Project report 6}, year = {2007}, institution = {INTEF Building and Infrastructure}, address = {Olso}, abstract = {

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.

}, keywords = {energy use, Passivhaus, thermal transmittance, U-value, window frame, windows}, isbn = {978-82-536-0970-6}, author = {Arlid Gustavsen and Bj{\o}rn Petter Jelle and Dariush K. Arasteh and Christian Kohler} } @conference {1935, title = {Two-Dimensional Computational Fluid Dynamics and Conduction Simulations of Heat Transfer in Horizontal Window Frames with Internal Cavities}, booktitle = {2007 ASHRAE Winter Meeting}, year = {2007}, month = {01/2007}, address = {Dallas, TX}, abstract = {

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.

}, author = {Arlid Gustavsen and Christian Kohler and Arvid Dalehaug and Dariush K. Arasteh} } @techreport {58258, title = {Experimental Validation of Daylighting Simulation Methods for Complex Fenestration Systems}, year = {2006}, month = {05/2006}, abstract = {

The objective of this paper is to assess the capability of existing lighting simulation methods to predict the performance of complex fenestration systems, which are becoming a commonly used component in buildings construction domain. A specific experimental protocol was conducted to collect reliable reference data based on illuminance measurements inside a black box with (and without) one complex glazing sample facing a measured external luminance distribution. Two types of simulation methods were tested and compared: The first is based on modeling the glazing sample in a ray-tracing simulation program and the second is based on use of the samples{\textquoteright} BTDF data. The BTDF data sets were combined with the external luminance distribution to predict the flux distribution inside the room and the resulting illuminance values at the reference points. The comparison between the experimental reference data and the simulation results showed that the influence of the CFS could be predicted with good accuracy.

}, author = {Fawaz Maamari and Marilyn Andersen and Jan de Boer and William L. Carroll and Dominique Dumortier and Phillip Greenup} } @conference {12166, title = {Performance Criteria for Residential Zero Energy Windows}, booktitle = {2007 ASHRAE Winter Meeting}, year = {2006}, month = {01/2007}, address = {Dallas, TX}, abstract = {

This paper shows that the energy requirements for today{\textquoteright}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).

}, author = {Dariush K. Arasteh and Howdy Goudey and Yu Joe Huang and Christian Kohler and Robin Mitchell} } @techreport {1768, title = {RESFEN5: Program Description}, year = {2005}, month = {05/2005}, institution = {Lawrence Berkeley National Laboratory}, abstract = {

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{\textquoteright}s efforts.

}, author = {Robin Mitchell and Yu Joe Huang and Dariush K. Arasteh and Charlie Huizenga and Steve Glendenning} } @conference {1934, title = {Two-Dimension Conduction and CFD Simulations for Heat Transfer in Horizontal Window Frame Cavities}, booktitle = {2005 ASHRAE Winter Meeting}, volume = {111}, year = {2005}, month = {02/2005}, address = {Orlando, FL}, abstract = {

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.

}, author = {Arlid Gustavsen and Dariush K. Arasteh and Christian Kohler and Dragan C. Curcija} } @techreport {1400, title = {Evaluation of High Dynamic Range Photography as a Luminance Mapping Technique}, year = {2004}, abstract = {

The potential, limitations, and applicability of the High Dynamic Range (HDR) photography technique is evaluated as a luminance mapping tool. Multiple exposure photographs of static scenes are taken with a Nikon 5400 digital camera to capture the wide luminance variation within the scenes. The camera response function is computationally derived using the Photosphere software, and is used to fuse the multiple photographs into HDR images. The vignetting effect and point spread function of the camera and lens system is determined. Laboratory and field studies have shown that the pixel values in the HDR photographs can correspond to the physical quantity of luminance with reasonable precision and repeatability.

}, author = {Mehlika Inanici and Jim Galvin} } @techreport {1428, title = {A First-Generation Prototype Dynamic Residential Window}, year = {2004}, month = {10/2004}, pages = {11}, abstract = {

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.

}, author = {Christian Kohler and Howdy Goudey and Dariush K. Arasteh} } @conference {1936, title = {Two-Dimensional Computational Fluid Dynamics and Conduction Simulations of Heat Transfer in Window Frames with Internal Cavities - Part 1: Cavities Only}, booktitle = {ASHRAE Winter Meeting}, year = {2003}, month = {02/2005}, address = {Orlando, FL}, abstract = {

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.

}, author = {Arlid Gustavsen and Christian Kohler and Dariush K. Arasteh and Dragan C. Curcija} } @article {11955, title = {In Situ X-Ray Absorption Spectroscopy Study of Hydrogen Absorption by Nickel-Magnesium Thin Films}, journal = {Physical Review B}, volume = {67}, number = {8}, year = {2002}, month = {02/2003}, abstract = {

Structural and electronic properties of co-sputtered Ni-Mg thin films with varying Ni to Mg ratio were studied by in situ x-ray absorption spectroscopy in the Ni L-edge and Mg K-edge regions. Codeposition of the metals led to increased disorder and decreased coordination around Ni and Mg compared to pure metal films. Exposure of the metallic films to hydrogen resulted in formation of hydrides and increased disorder. The presence of hydrogen as a near neighbor around Mg caused a drastic reduction in the intensities of multiple scattering resonances at higher energies. The optical switching behavior and changes in the x-ray spectra varied with Ni to Mg atomic ratio. Pure Mg films with Pd overlayers were converted to MgH2: The H atoms occupy regular sites as in bulk MgH2. Although optical switching was slow in the absence of Ni, the amount of H2 absorption was large. Incorporation of Ni in Mg films led to an increase in the speed of optical switching but decreased maximum transparency. Significant shifts in the Ni L3 and L2 peaks are consistent with strong interaction with hydrogen in the mixed films.

}, doi = {10.1103/PhysRevB.67.085106}, author = {Baker Farangis and Ponnusamy Nachimuthu and Thomas J. Richardson and Jonathan L. Slack and Rupert C.C. Perera and Eric M. Gullikson and Dennis W. Lindle and Michael D. Rubin} } @conference {11970, title = {Infrared Thermography Measurements of Window Thermal Test Specimen: Surface Temperatures}, booktitle = {ASHRAE Seminar}, year = {2001}, month = {01/2002}, address = {Atlantic City, NJ}, abstract = {

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.

}, author = {Brent T. Griffith and Howdy Goudey and Dariush K. Arasteh} } @techreport {1893, title = {THERM 5.0 User{\textquoteright}s Manual}, year = {2001}, author = {Windows and Daylighting Group} } @article {12093, title = {Natural Convection Effects in Three-Dimensional Window Frames with Internal Cavities}, journal = {ASHRAE Transactions}, volume = {107, Part 2}, year = {2000}, month = {06/2001}, address = {Cincinnati, Ohio}, abstract = {

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.

}, author = {Arlid Gustavsen and Brent T. Griffith and Dariush K. Arasteh} } @article {1911, title = {Three-Dimensional Conjugate Computational Fluid Dynamics Simulations of Internal Window Frame Cavities Validated Using IR Thermography}, journal = {ASHRAE Transactions}, volume = {107}, year = {2000}, month = {06/2001}, pages = {538-549}, address = {Cincinnati, Ohio}, abstract = {

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 {\textdegree}C and 20 {\textdegree}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 {\textdegree}C and 3 mm and an estimated uncertainty of +/-0.5 {\textdegree}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.

}, author = {Arlid Gustavsen and Brent T. Griffith and Dariush K. Arasteh} } @conference {1890, title = {THERM 2.0: A Building Component Model for Steady-State Two-Dimensional Heat Transfer}, booktitle = {Building Simulation 99, International Building Performance Simulation Association (IBPSA)}, year = {1999}, month = {09/1999}, address = {Kyoto, Japan}, abstract = {

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.

}, author = {Charlie Huizenga and Dariush K. Arasteh and Elizabeth U. Finlayson and Robin Mitchell and Brent T. Griffith and Dragan C. Curcija} } @article {11805, title = {Ellipsometry on Sputter Deposited Tin Oxide Films: Optical Constants Versus Stoichiometry Hydrogen Content, and Amount of Electrochemically Intercalated Lithium}, journal = {Applied Optics}, volume = {37}, number = {31}, year = {1998}, pages = {7734-7741}, abstract = {

Tin oxide thin films were deposited by reactive radio-frequency magnetron sputtering onto In2O3:Sn coated and bare glass substrates. Optical constants in the 300-2500 nm wavelength range were determined by a combination of variable-angle spectroscopic ellipsometry and spectrophotometric transmittance measurements. Surface roughness was modeled from optical measurements and compared with atomic-force microscopy. The two techniques gave consistent results. The fit between experimental optical data and model results could be significantly improved when it was assumed that the refractive index of the Sn oxide varied across the film thickness. Varying the oxygen partial pressure during deposition made it possible to obtain films whose complex refractive index changed at the transition from SnO to SnO2. An addition of hydrogen gas during sputtering led to lower optical constants in the full spectral range in connection with a blue shift of the band gap. Electrochemical intercalation of lithium ions into the Sn oxide films raised their refractive index and enhanced their refractive-index gradient.

}, author = {Jan Isidorsson and Claes G. Granqvist and Klaus von Rottkay and Michael D. Rubin} } @conference {11866, title = {Experimental Techniques for Measuring Temperature and Velocity Fields to Improve the Use and Validation of Building Heat Transfer Models}, booktitle = {Thermal Performance of the Exterior Envelopes of Buildings VII}, year = {1998}, month = {12/1998}, address = {Clearwater Beach, FL}, abstract = {

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.

}, author = {Brent T. Griffith and Daniel Turler and Howdy Goudey and Dariush K. Arasteh} } @article {12144, title = {Optical Constants of Sputter-Deposited Ti-Ce Oxide and Zr-Ce Oxide Films}, journal = {Applied Optics}, volume = {37}, number = {25}, year = {1998}, month = {09/1998}, pages = {5993-6001}, chapter = {5993}, abstract = {

Films of Ti oxide, Zr oxide, Ce oxide, Ti-Ce oxide, and Zr-Ce oxide were made by means of reactive dc magnetron sputtering in a multitarget arrangement. The films were characterized by x-ray diffraction and electrochemical measurements, both techniques being firmly connected to stoichiometric information. The optical constants n and k were evalued from spectrophotometry and from variable-angle spectroscopic ellipsometry. The two analyses gave consistent results. It was found that n for the mixed-oxide films varied smoothly between the values for the pure oxides, whereas k in the band-gap range showed characteristic differences between Ti-Ce oxide and Zr-Ce oxide. It is speculated that this difference is associated with structural effects.

}, doi = {10.1364/AO.37.005993}, author = {Monica Veszelei and Lisen Kullman and Claes G. Granqvist and Klaus von Rottkay and Michael D. Rubin} } @conference {12207, title = {Rapid field testing of low-emittance coated glazings for product verification}, booktitle = {ASHRAE/DOE/BTECC Conference, Thermal Performance of the Exterior Envelopes of Buildings VII}, year = {1998}, month = {12/1998}, address = {Clearwater Beach, Florida}, abstract = {

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.

}, author = {Brent T. Griffith and Christian Kohler and Howdy Goudey and Daniel Turler and Dariush K. Arasteh} } @article {1880, title = {Teaching Students about Two-Dimensional Heat Transfer Effects in Buildings, Building Components, Equipment, and Appliances Using THERM 2.0}, journal = {ASHRAE Transactions}, volume = {105, Part 1}, year = {1998}, month = {01/1999}, address = {Chicago, IL}, abstract = {

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.

}, author = {Charlie Huizenga and Dariush K. Arasteh and Elizabeth U. Finlayson and Robin Mitchell and Brent T. Griffith} } @article {11949, title = {Improving Computer Simulations of Heat Transfer for Projecting Fenestration products: Using Radiation View-Factor Models}, journal = {ASHRAE Transactions}, volume = {104, Part 1}, number = {Part 1}, year = {1997}, abstract = {

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.

}, author = {Brent T. Griffith and Dragan C. Curcija and Daniel Turler and Dariush K. Arasteh} } @article {1794, title = {The Significance of Bolts in the Thermal Performance of Curtain-Wall Frames for Glazed Fa{\c c}ades}, journal = {ASHRAE Transactions}, volume = {104, Part 1}, year = {1997}, month = {01/1998}, address = {San Francisco, CA}, abstract = {

Curtain walls are assemblies of glazings and metal frames that commonly form the exterior glass fa{\c c}ades 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.

}, author = {Brent T. Griffith and Elizabeth U. Finlayson and Mehry Yazdanian and Dariush K. Arasteh} } @conference {11894, title = {Gas Filled Panels: An Update on Applications in the Building Thermal Envelope}, booktitle = {BETEC Fall Symposium, Superinsulations and the Building Envelope}, year = {1995}, month = {11/1995}, address = {Washington, DC}, abstract = {

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.

}, author = {Brent T. Griffith and Dariush K. Arasteh and Daniel Turler} } @techreport {58588, title = {An Infrared Thermography-Based Window Surface Temperature Database for the Validation of Computer Heat Transfer Models}, year = {1995}, month = {03/1995}, abstract = {

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 {\textquoteright}an absolute measurement accuracy of {\textpm}O.5{\textdegree}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.

}, author = {Fredric A. Beck and Brent T. Griffith and Daniel Turler and Dariush K. Arasteh} } @conference {12004, title = {Issues Associated with the Use of Infrared Thermography for Experimental Testing of Insulated Systems}, booktitle = {Thermal Performance of the Exterior Envelopes of Buildings VI Conference }, year = {1995}, month = {12/1995}, address = {Clearwater Beach, FL}, abstract = {

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 {\textdegree}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 {\textpm}0.5 {\textdegree}C for ambient air and background radiation at 21.1 {\textdegree}C and surface temperatures from 0 {\textdegree}C to 21 {\textdegree}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.

}, author = {Brent T. Griffith and Fredric A. Beck and Dariush K. Arasteh and Daniel Turler} } @article {1872, title = {Surface Temperatures of Insulated Glazing Units: Infrared Thermography Laboratory Measurements}, journal = {ASHRAE Transactions}, volume = {102}, year = {1995}, month = {12/1995}, abstract = {

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 {\textdegree}C (70 {\textdegree}F) and -17.8 {\textdegree}C (0 {\textdegree}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 {\textdegree}F) for the warm-side and 28.9 W/m2 K (5.1 Btu/h ft2 {\textdegree}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.

}, author = {Brent T. Griffith and Daniel Turler and Dariush K. Arasteh} } @article {1900, title = {Thermal Annealing Characteristics of Si and Mg-implanted GaN Thin Films}, journal = {Applied Physics Letters}, volume = {68}, number = {19}, year = {1995}, month = {03/1996}, pages = {2702-2704}, chapter = {2702}, abstract = {

In this letter, we report the results of ion implantation of GaN using 28Si and 23Mg species. Structural and electrical characterizations of the GaN thin films after thermal annealing show that native defects in the GaN films dominate over implant doping effects. The formation energies of the annealing induced defects are estimated to range from 1.4 to 3.6 eV. A 30 keV10^14 cm-2 Mg implant results in the decrease of the free-carrier concentration by three orders of magnitude compared to unimplanted GaN up to an annealing temperature of 690 {\textdegree}C. Furthermore, we have observed the correlation between these annealing-induced defects to both improved optical and electrical properties.

}, keywords = {annealing, crystal doping, defect states, electrical properties, gallium nitrides, ion implantation, magnesium additions, microstructure, silicon additions}, issn = {0003-6951}, doi = {10.1063/1.116314}, author = {James S. Chan and Nathan W. Cheung and Lawrence F. Schloss and Erin C. Jones and William S. Wong and Nathan Newman and Xiaohong Liu and Eicke R. Weber and A. Gassman and Michael D. Rubin} } @conference {1946, title = {Using Infrared Thermography for the Creation of a Window Surface Temperature Database to Validate Computer Heat Transfer Models}, booktitle = {Windows Innovations Conference 95}, year = {1995}, month = {06/1995}, address = {Toronto, Canada}, abstract = {

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.

}, author = {Fredric A. Beck and Brent T. Griffith and Daniel Turler and Dariush K. Arasteh} } @techreport {1447, title = {Glazing Material for Solar and Architectural Applications}, year = {1994}, month = {09/1994}, abstract = {

This report summarizes five collaborative research projects on glazings performed by participants in Subtask C of IEA Solar Heating and Cooling Programme (SHC) Task 10, Materials Research and Testing. The projects include materials characterization, optical and thermal measurements, and durability testing of several types of new glazings. Three studies were completed on electrochromic and dispersed liquid crystals for smart windows, and two were completed for low-E coatings and transparent insulation materials for more conventional window and wall applications. In the area of optical switching materials for smart windows, the group developed more uniform characterization parameters that are useful to determine lifetime and performance of electrochromics. The detailed optical properties of an Asahi (Japan) prototype electrochromic window were measured in several laboratories. A one square meter array of prototype devices was tested outdoors and demonstrated significant cooling savings compared to tinted static glazing. Three dispersed liquid crystal window devices from Taliq (USA) were evaluated. In the off state, these liquid crystal windows scatter light greatly. When a voltage of about 100 V ac is applied, these windows become transparent. Undyed devices reduce total visible light transmittance by only .25 when switched, but this can be increased to .50 with the use of dyed liquid crystals. A wide range of solar-optical and emittance measurements were made on low-E coated glass and plastic. Samples of pyrolytic tin oxide from Ford glass (USA) and multilayer metal-dielectric coatings from Interpane (Germany) and Southwall (USA) were evaluated. In addition to optical characterization, the samples were exposure-tested in Switzerland. The thermal and optical properties of two different types of transparent insulation materials were measured. Samples of the polycarbonate honeycomb (supplied by Arel in Israel) and monolithic aerogel (supplied by Airglass in Sweden) were evaluated. Discrepancies in the round robin thermal measurements for the honeycomb material pointed out some measurement problems due to different equipment and procedures used. Overall, these glazing studies were successful in improving the understanding and use of advanced glazings. Follow-on work on most of these glazings will be continued in the new IEA SHC Task 18, Advanced Glazing Materials.

}, author = {Windows and Daylighting Group}, editor = {Carl M Lampert} } @conference {11987, title = {Integrated Window Systems: An Advanced Energy-Efficient Residential Fenestration Product}, booktitle = {19th National Passive Solar Conference}, year = {1994}, month = {06/1994}, address = {San Jose, CA}, abstract = {

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.

}, author = {Dariush K. Arasteh and Brent T. Griffith and Paul LaBerge} } @conference {11610, title = {Characteristics of Laminated Electrochromic Devices Using Polyorganodisulfate Electrodes}, booktitle = {SPIE Proceedings 2017}, year = {1993}, pages = {143}, abstract = {

The use of polyorganodisulfides as optically passive counterelectrodes in a variety of electrochromic devices are discussed. Characteristic data is presented for electrochmmic devices using proton, and lithium coloration ions with polyethylene oxide electrolyte and polydimercaptothiadiazole positive electrodes. Solid state devices consisting of molybdenum doped W03, amorphous polyethylene oxide electrolyte (a-PEO), and a polyorganodisulfide counter-electrode colored rapidly from a pale yellow to a deep blue-green, upon application of 1.2 V d.c. The photopic transmittance changed from 61 to 98, and the solar transmittance from 45 to 5\% during the coloration process. Also, our experiments with polyimidazole are detailed. This family of compounds due to its unique electrical and ion conduction properties allow a single composite ion storage and ion conductor electrode to be made, simplifying the device construction. Devices rnade from this family of compounds color to deep blue-gray upon application of 1.2-1.5 V. Bleaching occurs at -0.4 to -0.5 s. The photopic transmittance changed from 55 to 9\%. and the solar transmittance from 34 to 4\% during coloration. Both coloration and bleaching are quite rapid.

}, author = {Carl M Lampert and Steven J. Visco and Marca M. Doeff and Yan Ping Ma and Yongxiang He and Jean-Christophe Giron} } @conference {12156, title = {Optimizing the Effective Conductivity and Cost of Gas-Filled Panel Thermal Insulations}, booktitle = {22nd International Thermal Conductivity Conference}, year = {1993}, month = {11/1993}, address = {Tempe, AZ}, abstract = {

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.

}, author = {Brent T. Griffith and Daniel Turler and Dariush K. Arasteh} }