TY - JOUR T1 - Daylight performance of a microstructured prismatic window film in deep open plan offices JF - Building and Environment Y1 - 2017/02// SP - 280 EP - 297 A1 - Andrew McNeil A1 - Eleanor S. Lee A1 - Jacob C. Jonsson AB - Daylight redirecting systems with vertical windows have the potential to offset lighting energy use in deep perimeter zones. A microstructured prismatic film designed for such use was characterized using goniophotometric measurements and ray tracing simulations. The synthetically-generated bidirectional scattering distribution function (BSDF) data were shown to have good agreement with limited measured data for normal incident angles (0–60°). Measured data indicated that the prismatic film was most efficient when vertical angles of incidence were between 18 and 35° and within ±45° of normal incidence to the plane of the window so maximum energy savings across the full depth of the zone occurred over the equinox to winter solstice period. Annual lighting energy use and visual comfort in a deep open plan office zone were evaluated using the Radiance three-phase method in several climates and for south and east-facing window orientations. Lighting energy savings were 39–43% for a 12 m (40 ft) deep south-facing perimeter zone compared to the same zone with no lighting controls. The prismatic film with and without a diffuser controlled glare for views parallel to the window but produced glare for seated viewpoints looking toward the window. At mature market costs, the system was projected to have a simple payback of 2–6 years. Technical challenges encountered throughout the evaluation led to improvements in measurement and modeling tools and stressed the importance of having accurate input data for product development. VL - 113 U2 - LBNL-2001167 DO - 10.1016/j.buildenv.2016.07.019 ER - TY - RPRT T1 - Angular selective window systems: Assessment of technical potential for energy saving Y1 - 2014/01// SP - 36 A1 - Luis L. Fernandes A1 - Eleanor S. Lee A1 - Andrew McNeil A1 - Jacob C. Jonsson A1 - Thierry Stephane Nouidui A1 - Xiufeng Pang A1 - Sabine Hoffmann KW - angular selective systems KW - Building energy-efficiency KW - daylighting KW - Shading Systems KW - windows AB - Static angular selective shading systems block or filter direct sunlight and admit daylight within a specific range of incident solar angles. They can potentially deliver energy efficient performance within the typical 4.6-m (15-ft) deep perimeter zone of buildings when tailored to a specific façade orientation and latitude. The objective of this study is to quantify the technical potential of these systems to reduce energy use and peak demand in commercial buildings, specifically: a) achieve 30-50% reductions in perimeter zone energy use vs. ASHRAE 90.1-2004, b) constrain peak window loads to less than 43 W/m2-floor (4 W/ft2-floor), and c) to the extent possible, admit useful daylight in the perimeter zone without exceeding the peak solar load constraint. Three distinctly different commercial shading systems were evaluated: a micro-perforated screen, a tubular shading structure (double- and triple-paned configurations), and an expanded metal mesh. This evaluation was performed mainly through computer simulation for a multitude of scenarios, including multiple climates (Chicago, Illinois and Houston, Texas), window-to-wall ratios (0.15-0.60), building codes (ASHRAE 90.1-2004 and 2010) and lighting control configurations (with and without daylighting controls). Angular selective shading systems are optically complex and cannot be modeled accurately using conventional simulation tools, prompting the development of unique versions of the EnergyPlus, Radiance and Window simulation tools. Results show significant potential reductions in perimeter zone energy use, with the best commercially-available system reaching 28% and 47% savings, relative to ASHRAE 90.1- 2004 and respectively without and with daylighting controls, on south facades in Chicago with WWR=0.45, while constraining peak window heat gains to under 43 W/m2-floor, and enabling significant savings from daylighting controls. Results suggest that it is possible that existing systems can be improved to more consistently achieve 30-50% energy savings. Level of angular selectivity, spectral selectivity of low-e coatings and thermal conductance of the angle-selective layer were identified as critical factors for the performance of angular selective systems. Static, angular selective shading systems offer a potentially low-cost option to significantly reduce window heat gains and control glare from visibility of the sun orb, while permitting the admission of useful daylight and access to views to the outdoors. This type of system shows significant potential to contribute towards net-zero energy goals in both new and retrofit construction. N1 -

Submitted to Energy and Buildings, May 27, 2014

U2 - LBNL-187060 ER - TY - RPRT T1 - Daylight performance of a microstructured prismatic window film in deep open plan offices Y1 - 2013/09// A1 - Andrew McNeil A1 - Eleanor S. Lee A1 - Jacob C. Jonsson AB - Daylight redirecting systems with vertical windows have the potential to offset lighting energy use in deep perimeter zones. A microstructured prismatic film was designed and fabricated by a manufacturer to redirect sunlight to the ceiling plane when the film was installed in the upper portion of a window. Energy simulations based on the raytracing program, Radiance, were performed to evaluate the annual lighting energy use and discomfort glare in a deep open plan office zone in several climates and for south and east-facing window orientations. These simulations showed that when the prismatic film was combined with a light diffusing film, the system was able to deliver significant energy savings without glare. JF - DOE/ CEC PIER Technical Report ER - TY - RPRT T1 - A Pilot Demonstration of Electrochromic and Thermochromic Windows in the Denver Federal Center, Building 41, Denver, Colorado Y1 - 2013/07// A1 - Eleanor S. Lee A1 - Luis L. Fernandes A1 - Howdy Goudey A1 - Jacob C. Jonsson A1 - Dragan C. Curcija A1 - Xiufeng Pang A1 - Dennis L. DiBartolomeo A1 - Sabine Hoffmann KW - building controls KW - daylighting KW - Demand Side Management KW - electrochromic KW - energy-efficiency KW - Smart windows KW - switchable windows KW - Thermochromic KW - Window AB - 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. UR - http://gsa.gov/portal/content/187967 N1 -

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

U2 - LBNL-1005095 ER - TY - RPRT T1 - Theory documentation for software to control the pgII phirot2 automated sample mount and analyzing data obtained Y1 - 2013/09// A1 - Jacob C. Jonsson AB - The phirot2 sample holder is a device used for controlling the angle of incidence for anisotropic samples with the pgII photogoniometer.The first topic covered is how to control the instrument using the allmess command line tool which allows the measurement sequence to be more flexible than the pgc GUI tool usually used for control. A method to monitor drift over long measurement sessions is also covered. Tangential to this is several syntax examples of how bash shell script is used to call allmess. Code to generate bash scripts for samples with different degree of symmetry is discussed as well as how to modify a script to continue from a certain point if a measurement was aborted.The second half of the document describes how to access the data and compile the data into the Klems XML format. A path for future combination with the Radiance interpolation format is also given.Finally verification and visualization of BSDF data is discussed. CY - Berkeley ER - TY - JOUR T1 - A validation of a ray-tracing tool used to generate bi-directional scattering distribution functions for complex fenestration systems JF - Solar Energy Y1 - 2013/12// SP - 404 EP - 414 A1 - Andrew McNeil A1 - Jacob C. Jonsson A1 - Appelfeld, David A1 - Gregory J. Ward A1 - Eleanor S. Lee KW - Bi-directional scattering distribution function KW - Complex fenestration systems KW - daylighting KW - Solar heat gain AB - Fenestration attachments are anticipated to produce significant reductions in building energy use because they can be deployed quickly at low-cost. New software tools enable users to assess the building energy impacts of optically complex fenestration systems (CFS) such as shades, Venetian blinds, or daylighting systems. However, such tools require users to provide bi-directional scattering distribution function (BSDF) data that describe the solar-optical performance of the CFS. A free, open-source Radiance tool genBSDF enables users to generate BSDF data for arbitrary CFS. Prior to genBSDF, BSDF data for arbitrary fenestration systems could only be produced using either expensive software or with expensive equipment. genBSDF outputs CFS data in the Window 6 XML file format and so can be used with CFS-enabled software tools to model multi-layered window systems composed of glazing and shading layers.We explain the basis and use of the genBSDF tool and validate the tool by comparing results for four different cases to BSDF data produced via alternate methods. This validation demonstrates that BSDFs created with genBSDF are comparable to BSDFs generated analytically using TracePro and by measurement with a scanning goniophotometer. This tool is expected to support accelerated adoption of fenestration attachments and daylighting technologies. VL - 98 IS - C U2 - LBNL-6541E DO - 10.1016/j.solener.2013.09.032 ER - TY - JOUR T1 - Fenestration of Today and Tomorrow: A State-of-the-Art Review and Future Research Opportunities JF - Solar Energy Materials and Solar Cells Y1 - 2012/01// SP - 1 EP - 28 A1 - Bjørn Petter Jelle A1 - Andrew Hynd A1 - Arlid Gustavsen A1 - Dariush K. Arasteh A1 - Howdy Goudey A1 - Robert Hart KW - Fenestration KW - Low-e KW - Multilayer glazing KW - Smart window KW - Solar cell glazing KW - Vacuum glazing AB - 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. VL - 96 U1 -

Windows and Daylighting Group

U2 - LBNL-5304E DO - 10.1016/j.solmat.2011.08.010 ER - TY - JOUR T1 - Key Elements of and Materials Performance Targets for Highly Insulating Window Frames JF - Energy and Buildings Y1 - 2011/10// SP - 2583 EP - 2594 A1 - Arlid Gustavsen A1 - Steinar Grynning A1 - Dariush K. Arasteh A1 - Bjørn Petter Jelle A1 - Howdy Goudey KW - Fenestration KW - heat transfer modeling KW - thermal performance KW - thermal transmittance KW - u-factor KW - window frames AB - 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. VL - 43 IS - 10 U1 -

Windows and Daylighting Group

U2 - LBNL-5099E DO - 10.1016/j.enbuild.2011.05.010 ER - TY - JOUR T1 - Performance of Integrated Systems of Automated Roller Shade Systems and Daylight Responsive Dimming Systems JF - Building and Environment Y1 - 2011/03// SP - 747 EP - 757 A1 - Byoung-Chul Park A1 - An-Seop Choi A1 - Jae-Weon Jeong A1 - Eleanor S. Lee KW - automated roller shade systems KW - daylight responsive dimming systems KW - daylighting KW - Integrated systems KW - photoelectric controls AB - Daylight responsive dimming systems have been used in few buildings to date because they require improvements to improve reliability. The key underlying factor contributing to poor performance is the variability of the ratio of the photosensor signal to daylight workplane illuminance in accordance with sun position, sky condition, and fenestration condition. Therefore, this paper describes the integrated systems between automated roller shade systems and daylight responsive dimming systems with an improved closed-loop proportional control algorithm, and the relative performance of the integrated systems and single systems. The concept of the improved closed-loop proportional control algorithm for the integrated systems is to predict the varying correlation of photosensor signal to daylight workplane illuminance according to roller shade height and sky conditions for improvement of the system accuracy. In this study, the performance of the integrated systems with two improved closed-loop proportional control algorithms was compared with that of the current (modified) closed-loop proportional control algorithm. In the results, the average maintenance percentage and the average discrepancies of the target illuminance, as well as the average time under 90% of target illuminance for the integrated systems significantly improved in comparison with the current closed-loop proportional control algorithm for daylight responsive dimming systems as a single system. VL - 46 IS - 3 U1 -

Windows and Daylighting Group

U2 - LBNL-4418E DO - 10.1016/j.buildenv.2010.10.007 ER - TY - JOUR T1 - Simulating the Daylight Performance of Complex Fenestration Systems Using Bidirectional Scattering Distribution Functions within Radiance JF - Leukos, The Journal of the Illuminating Engineering Society Y1 - 2011/04// A1 - Gregory J. Ward A1 - Richard G. Mistrick A1 - Eleanor S. Lee A1 - Andrew McNeil A1 - Jacob C. Jonsson KW - bidirectional scattering distribution function (BSDF) KW - Complex fenestration systems KW - daylighting systems KW - energy KW - Radiance software KW - Shading Systems KW - windows AB - We describe two methods which rely on bidirectional scattering distribution functions (BSDFs) to model the daylighting performance of complex fenestration systems (CFS), enabling greater flexibility and accuracy in evaluating arbitrary assemblies of glazing, shading, and other optically-complex coplanar window systems. Two tools within Radiance enable a) efficient annual performance evaluations of CFS, and b) accurate renderings of CFS despite the loss of spatial resolution associated with low-resolution BSDF datasets for inhomogeneous systems. Validation, accuracy, and limitations of the methods are discussed. VL - 7 IS - 4 U1 -

Windows and Daylighting Group

U2 - LBNL-4414E DO - 10.1080/15502724.2011.10732150 ER - TY - CONF T1 - Experimental and Numerical Examination of the Thermal Transmittance of High Performance Window Frames T2 - Thermal Performance of the Exterior Envelopes of Whole Buildings XI International Conference, December 5-9, 2010 Y1 - 2010/09// A1 - Arlid Gustavsen A1 - Goce Talev A1 - Dariush K. Arasteh A1 - Howdy Goudey A1 - Christian Kohler A1 - Sivert Uvsløkk A1 - Bjørn Petter Jelle KW - experimental KW - Fenestration KW - frame cavity KW - heat transfer modeling KW - hot box KW - international standards KW - thermal transmittance KW - U-value KW - window frames AB - 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. JF - Thermal Performance of the Exterior Envelopes of Whole Buildings XI International Conference, December 5-9, 2010 CY - Clearwater Beach, FL U1 -

Windows and Daylighting Group

U2 - LBNL-3886E ER - TY - JOUR T1 - Light-scattering properties of a Venetian blind slat used for daylighting applications JF - Solar Energy Y1 - 2010/12// SP - 2103 EP - 2111 A1 - Annica M. Nilsson A1 - Jacob C. Jonsson KW - ABg-model KW - BSDF KW - Raytracing KW - Venetian blinds AB - The low cost, simplicity, and aesthetic appearance of external and internal shading devices, make them commonly used for daylighting and glare-control applications. Shading devices, such as Venetian blinds, screens, and roller shades, generally exhibit light scattering and/or light redirecting properties. This requires the bi-directional scattering distribution function (BSDF) of the material to be known in order to accurately predict the daylight distribution and energy flow through the fenestration system. Acquiring the complete BSDF is not a straightforward task, and to complete the process it is often required that a model is used to complement the measured data. In this project, a Venetian blind slat with a white top surface and a brushed aluminum bottom surface was optically characterized. A goniophotometer and an integrating sphere spectrophotometer were used to determine the angle resolved and hemispherical reflectance of the sample, respectively. The acquired data were fitted to a scattering model providing one Lambertian and one angle dependent description of the surface properties. These were used in combination with raytracing to obtain the complete BSDFs of the Venetian blind system. VL - 84 IS - 12 JO - Solar Energy DO - 10.1016/j.solener.2010.09.005 ER - TY - JOUR T1 - Optical characterization of fritted glass for architectural applications JF - Optical Materials Y1 - 2009/ SP - 949 EP - 958 A1 - Jacob C. Jonsson A1 - Michael D. Rubin A1 - Annica M. Nilsson A1 - Andreas Jonsson A1 - Arne Roos KW - BRDF KW - BTDF KW - Fritted glass KW - Integrating sphere KW - light scattering AB - Fritted glass is commonly used as a light diffusing element in modern buildings. Traditionally it has been used for aesthetic purposes but it can also be used for energy savings by incorporating it in novel daylighting systems? To answer such questions the light scattering properties must be properly characterized.This paper contains measurements of different varieties of fritted glass, ranging from the simplest direct-hemispherical measurements to angle-resolved goniometer measurements. Modeling the light scattering to obtain the full bidirectional scattering distribution function (BSDF) extends the measured data, making it useful in simulation programs such as Window 6 and Radiance. Surface profilometry results and SEM micrographs are included to demonstrate the surface properties of the samples studied. VL - 31 IS - 6 JO - Optical Materials DO - 10.1016/j.optmat.2008.10.050 ER - TY - CONF T1 - Simulating Complex Window Systems Using BSDF Data T2 - 26th Conference on Passive and Low Energy Architecture (PLEA), June-22-24 Y1 - 2009/06// A1 - Maria Konstantoglou A1 - Jacob C. Jonsson A1 - Eleanor S. Lee AB - Nowadays, virtual models are commonly used to evaluate the performance of conventional window systems. Complex fenestration systems can be difficult to simulate accurately not only because of their geometry but also because of their optical properties that scatter light in an unpredictable manner. Bi-directional Scattering Distribution Functions (BSDF) have recently been developed based on a mixture of measurements and modelling to characterize the optics of such systems. This paper describes the workflow needed to create then use these BSDF datasets in the Radiance lighting simulation software. Limited comparisons are made between visualizations produced using the standard ray-tracing method, the BSDF method, and that taken in a full-scale outdoor mockup. JF - 26th Conference on Passive and Low Energy Architecture (PLEA), June-22-24 CY - Quebec City, Canada U1 -

Windows and Daylighting Group

U2 - LBNL-4416E ER - TY - JOUR T1 - Developing Low-Conductance Window Frames: Capabilities and Limitations of Current Window Heat Transfer Design Tools JF - Journal of Building Physics Y1 - 2008/ SP - 131 EP - 153 A1 - Arlid Gustavsen A1 - Dariush K. Arasteh A1 - Bjørn Petter Jelle A1 - Dragan C. Curcija A1 - Christian Kohler AB - 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: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.Assess 3-D radiation effects in frame cavities and develop recommendation for inclusion into the design fenestration tools.Assess existing correlations for convection in vertical cavities using CFD.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.Study 3 D hardware short-circuits and propose methods to ensure that these effects are incorporated into ratings.Study the heat transfer effects of ventilated frame cavities and propose updated correlations. VL - 32 U1 -

Windows and Daylighting Group

U2 - LBNL-1022E ER - TY - CONF T1 - Light-scattering properties of a woven shade-screen material used for daylighting and solar heat-gain control T2 - SPIE Optics+Photonics Y1 - 2008/08// A1 - Jacob C. Jonsson A1 - Eleanor S. Lee A1 - Michael D. Rubin AB - Shade-screens are widely used in commercial buildings as a way to limit the amount of direct sunlight that can disturb people in the building. The shade screens also reduce the solar heat-gain through glazing the system. Modern energy and daylighting analysis software such as EnergyPlus and Radiance require complete scattering properties of the scattering materials in the system.In this paper a shade screen used in the LBNL daylighting testbed is characterized using a photogoniometer and a normal angle of incidence integrating sphere. The data is used to create a complete bi-directional scattering distribution function (BDSF) that used in simulation programs.The resulting BDSF is compared to a model's BDSF, both directly and by calculating the solar heat-gain coefficient for a dual-pane system using Window 6. JF - SPIE Optics+Photonics CY - San Diego, CA U1 -

Windows and Daylighting Group

U2 - LBNL-828E ER - TY - CONF T1 - NFRC Interlaboratory Comparison on Optical Properties T2 - NFRC Conference Y1 - 2006/03// A1 - Jacob C. Jonsson A1 - Michael D. Rubin AB - As part of the NFRC rating process, optical data on glazing materials is combined with other information to calculate various properties of a window product. The administrative procedure for gathering such optical data is governed by NFRC 3021, which in turn refers to NFRC 3002 and NFRC 3013 for the technical procedures by which the optical properties are determined in the solar and infrared ranges, respectively. In practice, the data is compiled by the Lawrence Berkeley National Laboratory (LBNL) and becomes part of the International Glazing Database (IGDB).NFRC 302 specifies that submitters of optical data or their representatives must participate in a 'round robin' or ILC. Often, manufacturers of glazing materials have the optical equipment necessary to perform their own measurements. NFRC 302 allows manufacturers to submit their own measured data subject to a set of checks including peer review to ensure the accuracy of such data. In some cases the glazing manufacturer does not have the required equipment and so may choose to send the samples to a test laboratory. In other cases the manufacturer of the final product such as a laminate may ask a component supplier, often a glass manufacturer, to perform the measurements for them. In such cases the "representative" must have qualified by participating in the ILC. An ILC is only required every four years and it would be unfair to expect new product submitters to wait so long. Therefore, two interpretations are made on occasion: (1) a new data submitter does not have to wait for the next ILC if they submit a set of samples with their first dataset for comparison at LBNL (a mini ILC), or (2) if they have participated in an ILC conducted by some other reputable independent organization. JF - NFRC Conference CY - San Diego, CA U1 -

Windows and Daylighting Group

U2 - LBNL-501E ER - TY - JOUR T1 - Obtaining the Bidirectional Transfer Distribution Function of Isotropically Scattering Materials Using an Integrating Sphere JF - Optics Communications Y1 - 2007/ SP - 228 EP - 236 A1 - Jacob C. Jonsson A1 - Henrik Branden AB - This paper demonstrates a method to determine the bidirectional transfer distribution function (BTDF) using an integrating sphere. Information about the sample's angle dependent scattering is obtained by making transmittance measurements with the sample at different distances from the integrating sphere. Knowledge about the illuminated area of the sample and the geometry of the sphere port in combination with the measured data combines to an system of equations that includes the angle dependent transmittance. The resulting system of equations is an ill-posed problem which rarely gives a physical solution. A solvable system is obtained by using Tikhonov regularization on the ill-posed problem. The solution to this system can then be used to obtain the BTDF. Four bulk-scattering samples were characterised using both two goniophotometers and the described method to verify the validity of the new method. The agreement shown is great for the more diffuse samples. The solution to the low-scattering samples contains unphysical oscillations, but still gives the correct shape of the solution. The origin of the oscillations and why they are more prominent in low-scattering samples are discussed. VL - 277 U1 -

Windows and Daylighting Group

U2 - LBNL-61826 ER - TY - RPRT T1 - State-of-the-Art Highly Insulating Window Frames - Research and Market Review Y1 - 2007/ A1 - Arlid Gustavsen A1 - Bjørn Petter Jelle A1 - Dariush K. Arasteh A1 - Christian Kohler KW - energy use KW - Passivhaus KW - thermal transmittance KW - U-value KW - window frame KW - windows AB - 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. JF - SINTEF Building and Infrastructure PB - INTEF Building and Infrastructure CY - Olso SN - 978-82-536-0970-6 U1 -

Windows and Daylighting Group

U2 - LBNL-1133E ER - TY - BOOK T1 - Daylight in Buildings. A Source Book on Daylighting Systems and Components Y1 - 2001/ A1 - Nancy Ruck A1 - Øyvind Aschehoug A1 - Sirri Aydinli A1 - Jens Christoffersen A1 - Gilles Courret A1 - Ian Edmonds A1 - Roman Jakobiak A1 - Martin Kischkoweit-Lopin A1 - Martin Klinger A1 - Eleanor S. Lee A1 - Laurent Michel A1 - Jean-Louis Scartezzini A1 - Stephen E. Selkowitz UR - https://facades.lbl.gov/daylight-buildings-source-book-daylighting-systems N1 -

Download: Daylight in Buildings
A hard copy of the book may be obtained by sending a request to Ellen Thomas at EllenThomas@lbl.govOnly one copy per individual, U.S. or Canadians only.  If you reside elsewhere, go to http://task21.iea-shc.org/ to find out how to obtain a copy in your country. 

U1 -

Windows and Daylighting Group

U2 - LBNL-47493 ER - TY - JOUR T1 - Strain Related Phenomena in GaN Thin Films JF - Physical Review B Y1 - 1996/12// SP - 17745 EP - 17753 A1 - Christian F. Kisielowski A1 - Joachim Krüger A1 - Sergei Ruvimov A1 - Tadeusz Suski A1 - Joel W. Ager III A1 - Erin C. Jones A1 - Zuzanna Liliental-Weber A1 - Michael D. Rubin A1 - Eicke R. Weber A1 - Michael D. Bremser A1 - Robert F. Davis ED - Joachim Krüger AB - Photoluminescence (PL), Raman spectroscopy, and x-ray diffraction are employed to demonstrate the co-existence of a biaxial and a hydrostatic strain that can be present in GaN thin films. The biaxial strain originates from growth on lattice-mismatched substrates and from post-growth cooling. An additional hydrostatic strain is shown to be introduced by the presence of point defects. A consistent description of the experimental results is derived within the limits of the linear and isotropic elastic theory using a Poisson ratio nu =0.23+/-0.06 and a bulk modulus B=200+/-20 GPa. These isotropic elastic constants help to judge the validity of published anisotropic elastic constants that vary greatly. Calibration constants for strain-induced shifts of the near-band-edge PL lines with respect to the E2 Raman mode are given for strain-free, biaxially strained, and hydrostatically contracted or expanded thin films. They allow us to extract differences between hydrostatic and biaxial stress components if present. In particular, we determine that a biaxial stress of one GPa would shift the near-band-edge PL lines by 27+/-2 meV and the E2 Raman mode by 4.2+/-0.3 cm-1 by use of the listed isotropic elastic constants. It is expected from the analyses that stoichiometric variations in the GaN thin films together with the design of specific buffer layers can be utilized to strain engineer the material to an extent that greatly exceeds the possibilities known from other semiconductor systems because of the largely different covalent radii of the Ga and the N atom. VL - 54 IS - 24 U1 -

Windows and Daylighting Group

U2 - LBNL-39079 DO - 10.1103/PhysRevB.54.17745 ER - TY - JOUR T1 - The Influence of Nitrogen Ion Energy on the Quality of GaN Films Grown with Molecular Beam Epitaxy JF - Journal of Electronic Materials Y1 - 1995/04// SP - 249 EP - 255 A1 - T.C. Fu A1 - Nathan Newman A1 - Erin C. Jones A1 - James S. Chan A1 - Xiaohong Liu A1 - Michael D. Rubin A1 - Nathan W. Cheung A1 - Eicke R. Weber KW - Activated nitrogen KW - GaN KW - molecular beam epitaxy (MBE) KW - nitrogen ion energy AB - Since the growth of GaN using molecular beam epitaxy (MBE) occurs under metastable growth conditions, activated nitrogen is required to drive the forward synthesis reaction. In the process of exciting the nitrogen using a plasma or ion-beam source, species with large kinetic energies are generated. Impingement on the growth surface by these species can result in subsurface damage to the growing film, as well as an enhancement of the reverse decomposition reaction rate. In this study, we investigate the effect of the kinetic energy of the impinging nitrogen ions during growth on the resulting optical and structural properties of GaN films. Strong band-edge photoluminescence and cathodoluminescence are found when a kinetic energy of ~10 eV are used, while luminescence is not detectable when the kinetic energies exceeds 18 eV. Also, we find that the use of conductive SiC substrates results in more homogeneous luminescence than the use of insulating sapphire substrates. This is attributed to sample surface charging in the case of sapphire substrates and subsequent variation in the incident ion flux and kinetic energy across the growth surface.This study clearly shows that the quality of GaN films grown by MBE are presently limited by damage from the impingement of high energy species on the growth surface. VL - 24 IS - 4 U1 -

Windows and Daylighting Group

U2 - LBL-37223 DO - 10.1007/BF02659683 ER - TY - JOUR T1 - Thermal Annealing Characteristics of Si and Mg-implanted GaN Thin Films JF - Applied Physics Letters Y1 - 1996/03// SP - 2702 EP - 2704 A1 - James S. Chan A1 - Nathan W. Cheung A1 - Lawrence F. Schloss A1 - Erin C. Jones A1 - William S. Wong A1 - Nathan Newman A1 - Xiaohong Liu A1 - Eicke R. Weber A1 - A. Gassman A1 - Michael D. Rubin KW - annealing KW - crystal doping KW - defect states KW - electrical properties KW - gallium nitrides KW - ion implantation KW - magnesium additions KW - microstructure KW - silicon additions AB - 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 °C. Furthermore, we have observed the correlation between these annealing-induced defects to both improved optical and electrical properties. VL - 68 IS - 19 U1 -

Windows and Daylighting Group

U2 - LBL-37372 DO - 10.1063/1.116314 ER - TY - CONF T1 - Fundamental Materials-Issues Involved in the Growth of GaN by Molecular Beam Epitaxy Y1 - 1994/ A1 - Nathan Newman A1 - T.C. Fu A1 - Z. Liu A1 - Zuzanna Liliental-Weber A1 - Michael D. Rubin A1 - James S. Chan A1 - Erin C. Jones A1 - Jennifer T. Ross A1 - Ian M. Tidswell A1 - Kin Man Yu A1 - Nathan W. Cheung A1 - Eicke R. Weber AB - Gallium nitride is one of the most promising materials for ultraviolet and blue light-emitting diodes and lasers. Both Molecular Beam Epitaxy (MBE) and Metal-Organic Chemical Vapor Deposition (MOCVD) have recently made strong progress in fabricating high-quality epitaxial GaN thin films. In this paper, we review materials-related issues involved in MBE growth. We show that a strong understanding of the unique meta-stable growth process allows us to correctly predict the optimum conditions for epitaxial GaN growth. The resulting structural, electronic and optical properties of the GaN films are described in detail. U2 - LBL-37296 ER - TY - RPRT T1 - The Effects of Skylight Parameters on Daylighting Energy Savings Y1 - 1985/ A1 - Dariush K. Arasteh A1 - Russell Johnson A1 - Stephen E. Selkowitz AB - 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. U1 -

Windows and Daylighting Group

U2 - LBL-17456 ER - TY - JOUR T1 - Energy Performance and Savings Potentials with Skylights JF - ASHRAE Transactions Y1 - 1985/ SP - 154 EP - 179 A1 - Dariush K. Arasteh A1 - Russell Johnson A1 - Stephen E. Selkowitz A1 - Robert Sullivan AB - 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. VL - 91 U1 -

Windows and Daylighting Group

U2 - LBL-17457 ER - TY - CONF T1 - Skylight Energy Performance and Design Optimization T2 - Windows in Building Design and Maintanence Y1 - 1984/06// A1 - Dariush K. Arasteh A1 - Russell Johnson A1 - Robert Sullivan AB - 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. JF - Windows in Building Design and Maintanence CY - Gothenburg, Sweden U1 -

Windows and Daylighting Group

U2 - LBL-17476 ER -