02120nas a2200169 4500008004100000022001400041245009400055210006900149260001200218300001400230490000800244520157100252100001901823700002101842700002301863856006401886 2017 eng d a0360-132300aDaylight performance of a microstructured prismatic window film in deep open plan offices0 aDaylight performance of a microstructured prismatic window film  c02/2017 a280–2970 v1133 a

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.

1 aMcNeil, Andrew1 aLee, Eleanor, S.1 aJonsson, Jacob, C. uhttps://facades.lbl.gov/publications/daylight-performance-003492nas a2200253 4500008003900000245009000039210006900129260001200198300000700210520268100217653003002898653003102928653001602959653002002975653001202995100002403007700002103031700001903052700002303071700003103094700001803125700002103143856007403164 2014 d00aAngular selective window systems: Assessment of technical potential for energy saving0 aAngular selective window systems Assessment of technical potenti c01/2014 a363 a

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.

10aangular selective systems10aBuilding energy-efficiency10adaylighting10aShading Systems10awindows1 aFernandes, Luis, L.1 aLee, Eleanor, S.1 aMcNeil, Andrew1 aJonsson, Jacob, C.1 aNouidui, Thierry, Stephane1 aPang, Xiufeng1 aHoffmann, Sabine uhttps://facades.lbl.gov/publications/angular-selective-window-systems01223nas a2200133 4500008004100000245009400041210006900135260001200204520073200216100001900948700002100967700002300988856007801011 2013 eng d00aDaylight performance of a microstructured prismatic window film in deep open plan offices0 aDaylight performance of a microstructured prismatic window film  c09/20133 a

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.

1 aMcNeil, Andrew1 aLee, Eleanor, S.1 aJonsson, Jacob, C. uhttps://facades.lbl.gov/publications/daylight-performance-microstructured02423nas a2200301 4500008003900000245013000039210006900169260001200238520147600250653002201726653001601748653002701764653001901791653002201810653001801832653002301850653001801873653001101891100002101902700002401923700001801947700002301965700002401988700001802012700002902030700002102059856004102080 2013 d00aA Pilot Demonstration of Electrochromic and Thermochromic Windows in the Denver Federal Center, Building 41, Denver, Colorado0 aPilot Demonstration of Electrochromic and Thermochromic Windows  c07/20133 a

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.

10abuilding controls10adaylighting10aDemand Side Management10aelectrochromic10aenergy-efficiency10aSmart windows10aswitchable windows10aThermochromic10aWindow1 aLee, Eleanor, S.1 aFernandes, Luis, L.1 aGoudey, Howdy1 aJonsson, Jacob, C.1 aCurcija, Dragan, C.1 aPang, Xiufeng1 aDiBartolomeo, Dennis, L.1 aHoffmann, Sabine uhttp://gsa.gov/portal/content/18796701472nas a2200109 4500008004100000245011700041210006900158260002200227520101100249100002301260856007901283 2013 eng d00aTheory documentation for software to control the pgII phirot2 automated sample mount and analyzing data obtained0 aTheory documentation for software to control the pgII phirot2 au aBerkeleyc09/20133 a

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.

1 aJonsson, Jacob, C. uhttps://facades.lbl.gov/publications/theory-documentation-software-control02197nas a2200229 4500008003900000245013800039210006900177260001200246300001200258490000700270520138900277653005201666653003301718653001601751653002001767100001901787700002301806700002101829700002201850700002101872856007401893 2013 d00aA validation of a ray-tracing tool used to generate bi-directional scattering distribution functions for complex fenestration systems0 avalidation of a raytracing tool used to generate bidirectional s c12/2013 a404-4140 v983 a

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.

10aBi-directional scattering distribution function10aComplex fenestration systems10adaylighting10aSolar heat gain1 aMcNeil, Andrew1 aJonsson, Jacob, C.1 aAppelfeld, David1 aWard, Gregory, J.1 aLee, Eleanor, S. uhttps://facades.lbl.gov/publications/validation-ray-tracing-tool-used02582nas a2200265 4500008004100000245010000041210006900141260001200210300000900222490000700231520176600238653001702004653001002021653002302031653001702054653002302071653001902094100002602113700001702139700002102156700002502177700001802202700001702220856007902237 2012 eng d00aFenestration of Today and Tomorrow: A State-of-the-Art Review and Future Research Opportunities0 aFenestration of Today and Tomorrow A StateoftheArt Review and Fu c01/2012 a1-280 v963 a

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.

10aFenestration10aLow-e10aMultilayer glazing10aSmart window10aSolar cell glazing10aVacuum glazing1 aJelle, Bjørn, Petter1 aHynd, Andrew1 aGustavsen, Arlid1 aArasteh, Dariush, K.1 aGoudey, Howdy1 aHart, Robert uhttps://facades.lbl.gov/publications/fenestration-today-and-tomorrow-state02202nas a2200253 4500008004100000245009000041210006900131260001200200300001400212490000700226520141000233653001701643653002701660653002401687653002601711653001301737653001801750100002101768700002201789700002501811700002601836700001801862856006801880 2011 eng d00aKey Elements of and Materials Performance Targets for Highly Insulating Window Frames0 aKey Elements of and Materials Performance Targets for Highly Ins c10/2011 a2583-25940 v433 a

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.

10aFenestration10aheat transfer modeling10athermal performance10athermal transmittance10au-factor10awindow frames1 aGustavsen, Arlid1 aGrynning, Steinar1 aArasteh, Dariush, K.1 aJelle, Bjørn, Petter1 aGoudey, Howdy uhttps://facades.lbl.gov/publications/key-elements-and-materials02267nas a2200229 4500008004100000245011200041210006900153260001200222300001200234490000700246520149000253653003501743653004001778653001601818653002301834653002701857100002201884700001801906700002001924700002101944856007201965 2011 eng d00aPerformance of Integrated Systems of Automated Roller Shade Systems and Daylight Responsive Dimming Systems0 aPerformance of Integrated Systems of Automated Roller Shade Syst c03/2011 a747-7570 v463 a

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.

10aautomated roller shade systems10adaylight responsive dimming systems10adaylighting10aIntegrated systems10aphotoelectric controls1 aPark, Byoung-Chul1 aChoi, An-Seop1 aJeong, Jae-Weon1 aLee, Eleanor, S. uhttps://facades.lbl.gov/publications/performance-integrated-systems01571nas a2200277 4500008004100000022001400041050001500055245014200070210006900212260001200281490000600293520063000299653005800929653003300987653002401020653001101044653002201055653002001077653001201097100002201109700002601131700002101157700001901178700002301197856007301220 2011 eng d a1550-2724 aLBNL-4414E00aSimulating the Daylight Performance of Complex Fenestration Systems Using Bidirectional Scattering Distribution Functions within Radiance0 aSimulating the Daylight Performance of Complex Fenestration Syst c04/20110 v73 a

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.

10abidirectional scattering distribution function (BSDF)10aComplex fenestration systems10adaylighting systems10aenergy10aRadiance software10aShading Systems10awindows1 aWard, Gregory, J.1 aMistrick, Richard, G.1 aLee, Eleanor, S.1 aMcNeil, Andrew1 aJonsson, Jacob, C. uhttps://facades.lbl.gov/publications/simulating-daylight-performance02589nas a2200289 4500008004100000245010600041210006900147260003400216520165800250653001701908653001701925653001701942653002701959653001201986653002801998653002602026653001202052653001802064100002102082700001602103700002502119700001802144700002202162700002102184700002602205856006802231 2010 eng d00aExperimental and Numerical Examination of the Thermal Transmittance of High Performance Window Frames0 aExperimental and Numerical Examination of the Thermal Transmitta aClearwater Beach, FLc09/20103 a

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.

10aexperimental10aFenestration10aframe cavity10aheat transfer modeling10ahot box10ainternational standards10athermal transmittance10aU-value10awindow frames1 aGustavsen, Arlid1 aTalev, Goce1 aArasteh, Dariush, K.1 aGoudey, Howdy1 aKohler, Christian1 aUvsløkk, Sivert1 aJelle, Bjørn, Petter uhttps://facades.lbl.gov/publications/experimental-and-numerical01863nas a2200205 4500008003900000022001300039245009100052210006900143260001200212300001600224490000700240520122700247653001401474653000901488653001501497653002001512100002401532700002301556856007801579 2010 d a0038092X00aLight-scattering properties of a Venetian blind slat used for daylighting applications0 aLightscattering properties of a Venetian blind slat used for day c12/2010 a2103 - 21110 v843 a

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.

10aABg-model10aBSDF10aRaytracing10aVenetian blinds1 aNilsson, Annica, M.1 aJonsson, Jacob, C. uhttps://facades.lbl.gov/publications/light-scattering-properties-venetian01580nas a2200253 4500008003900000022001300039245007700052210006900129260001100198300001400209490000700223520083600230653000901066653000901075653001801084653002301102653002101125100002301146700002301169700002401192700002101216700001501237856007401252 2009 d a0925346700aOptical characterization of fritted glass for architectural applications0 aOptical characterization of fritted glass for architectural appl c4/2009 a949 - 9580 v313 a

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.

10aBRDF10aBTDF10aFritted glass10aIntegrating sphere10alight scattering1 aJonsson, Jacob, C.1 aRubin, Michael, D.1 aNilsson, Annica, M.1 aJonsson, Andreas1 aRoos, Arne uhttps://facades.lbl.gov/publications/optical-characterization-fritted01238nas a2200133 4500008004100000245005400041210005400095260003300149520077800182100002500960700002300985700002101008856007501029 2009 eng d00aSimulating Complex Window Systems Using BSDF Data0 aSimulating Complex Window Systems Using BSDF Data aQuebec City, Canadac06/20093 a

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.

1 aKonstantoglou, Maria1 aJonsson, Jacob, C.1 aLee, Eleanor, S. uhttps://facades.lbl.gov/publications/simulating-complex-window-systems02372nas a2200181 4500008004100000050001500041245012000056210006900176300001200245490000700257520173300264100002101997700002502018700002602043700002402069700002202093856007502115 2008 eng d aLBNL-1022E00aDeveloping Low-Conductance Window Frames: Capabilities and Limitations of Current Window Heat Transfer Design Tools0 aDeveloping LowConductance Window Frames Capabilities and Limitat a131-1530 v323 a

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.
1 aGustavsen, Arlid1 aArasteh, Dariush, K.1 aJelle, Bjørn, Petter1 aCurcija, Dragan, C.1 aKohler, Christian uhttps://facades.lbl.gov/publications/developing-low-conductance-window01399nas a2200145 4500008004100000050001400041245011400055210006900169260002700238520084600265100002301111700002101134700002301155856007501178 2008 eng d aLBNL-828E00aLight-scattering properties of a woven shade-screen material used for daylighting and solar heat-gain control0 aLightscattering properties of a woven shadescreen material used  aSan Diego, CAc08/20083 a

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.

1 aJonsson, Jacob, C.1 aLee, Eleanor, S.1 aRubin, Michael, D. uhttps://facades.lbl.gov/publications/light-scattering-properties-woven02234nas a2200133 4500008004100000050001400041245005800055210005800113260002700171520178300198100002301981700002302004856007302027 2007 eng d aLBNL-501E00aNFRC Interlaboratory Comparison on Optical Properties0 aNFRC Interlaboratory Comparison on Optical Properties aSan Diego, CAc03/20063 a

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.

1 aJonsson, Jacob, C.1 aRubin, Michael, D. uhttps://facades.lbl.gov/publications/nfrc-interlaboratory-comparison01753nas a2200145 4500008004100000050001500041245012900056210006900185300001200254490000800266520121600274100002301490700002001513856007401533 2007 eng d aLBNL-6182600aObtaining the Bidirectional Transfer Distribution Function of Isotropically Scattering Materials Using an Integrating Sphere0 aObtaining the Bidirectional Transfer Distribution Function of Is a228-2360 v2773 a

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.

1 aJonsson, Jacob, C.1 aBranden, Henrik uhttps://facades.lbl.gov/publications/obtaining-bidirectional-transfer03102nas a2200229 4500008004100000020002200041245008200063210006900145260004400214520234700258653001502605653001502620653002602635653001202661653001702673653001202690100002102702700002602723700002502749700002202774856007602796 2007 eng d a978-82-536-0970-600aState-of-the-Art Highly Insulating Window Frames - Research and Market Review0 aStateoftheArt Highly Insulating Window Frames Research and Marke aOlsobINTEF Building and Infrastructure3 a

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.

10aenergy use10aPassivhaus10athermal transmittance10aU-value10awindow frame10awindows1 aGustavsen, Arlid1 aJelle, Bjørn, Petter1 aArasteh, Dariush, K.1 aKohler, Christian uhttps://facades.lbl.gov/publications/state-art-highly-insulating-window00811nam a2200241 4500008004100000050001500041245007900056210006900135100001600204700002300220700001900243700002500262700002000287700001700307700002000324700003000344700002000374700002100394700002000415700002800435700002700463856007900490 2001 eng d aLBNL-4749300aDaylight in Buildings. A Source Book on Daylighting Systems and Components0 aDaylight in Buildings A Source Book on Daylighting Systems and C1 aRuck, Nancy1 aAschehoug, Øyvind1 aAydinli, Sirri1 aChristoffersen, Jens1 aCourret, Gilles1 aEdmonds, Ian1 aJakobiak, Roman1 aKischkoweit-Lopin, Martin1 aKlinger, Martin1 aLee, Eleanor, S.1 aMichel, Laurent1 aScartezzini, Jean-Louis1 aSelkowitz, Stephen, E. uhttps://facades.lbl.gov/daylight-buildings-source-book-daylighting-systems02402nas a2200265 4500008004100000245004700041210004700088260001200135300001600147490000700163520162000170100003101790700002101821700002001842700001901862700001901881700002001900700002901920700002301949700002101972700002501993700002202018700002102040856007502061 1996 eng d00aStrain Related Phenomena in GaN Thin Films0 aStrain Related Phenomena in GaN Thin Films c12/1996 a17745-177530 v543 a

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.

1 aKisielowski, Christian, F.1 aKrüger, Joachim1 aRuvimov, Sergei1 aSuski, Tadeusz1 aAger, Joel, W.1 aJones, Erin, C.1 aLiliental-Weber, Zuzanna1 aRubin, Michael, D.1 aWeber, Eicke, R.1 aBremser, Michael, D.1 aDavis, Robert, F.1 aKrüger, Joachim uhttps://facades.lbl.gov/publications/strain-related-phenomena-gan-thin02195nas a2200277 4500008004100000022001400041245010300055210006900158260001200227300001200239490000700251520133500258653002301593653000801616653003301624653002401657100001301681700001901694700002001713700002001733700001801753700002301771700002301794700002101817856007901838 1995 eng d a0361-523500aThe Influence of Nitrogen Ion Energy on the Quality of GaN Films Grown with Molecular Beam Epitaxy0 aInfluence of Nitrogen Ion Energy on the Quality of GaN Films Gro c04/1995 a249-2550 v243 a

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.

10aActivated nitrogen10aGaN10amolecular beam epitaxy (MBE)10anitrogen ion energy1 aFu, T.C.1 aNewman, Nathan1 aJones, Erin, C.1 aChan, James, S.1 aLiu, Xiaohong1 aRubin, Michael, D.1 aCheung, Nathan, W.1 aWeber, Eicke, R. uhttps://facades.lbl.gov/publications/influence-nitrogen-ion-energy-quality01809nas a2200361 4500008004100000022001400041245007600055210006900131260001200200300001400212490000700226520074400233653001400977653001900991653001801010653002601028653002101054653002101075653002401096653001901120653002201139100002001161700002301181700002601204700002001230700002201250700001901272700001801291700002101309700001601330700002301346856007801369 1995 eng d a0003-695100aThermal Annealing Characteristics of Si and Mg-implanted GaN Thin Films0 aThermal Annealing Characteristics of Si and Mgimplanted GaN Thin c03/1996 a2702-27040 v683 a

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.

10aannealing10acrystal doping10adefect states10aelectrical properties10agallium nitrides10aion implantation10amagnesium additions10amicrostructure10asilicon additions1 aChan, James, S.1 aCheung, Nathan, W.1 aSchloss, Lawrence, F.1 aJones, Erin, C.1 aWong, William, S.1 aNewman, Nathan1 aLiu, Xiaohong1 aWeber, Eicke, R.1 aGassman, A.1 aRubin, Michael, D. uhttps://facades.lbl.gov/publications/thermal-annealing-characteristics-si01409nas a2200241 4500008004100000050001400041245008900055210006900144520063300213100001900846700001300865700001200878700002900890700002300919700002000942700002000962700002300982700002201005700001701027700002301044700002101067856007901088 1994 eng d aLBL-3729600aFundamental Materials-Issues Involved in the Growth of GaN by Molecular Beam Epitaxy0 aFundamental MaterialsIssues Involved in the Growth of GaN by Mol3 a

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.

1 aNewman, Nathan1 aFu, T.C.1 aLiu, Z.1 aLiliental-Weber, Zuzanna1 aRubin, Michael, D.1 aChan, James, S.1 aJones, Erin, C.1 aRoss, Jennifer, T.1 aTidswell, Ian, M.1 aYu, Kin, Man1 aCheung, Nathan, W.1 aWeber, Eicke, R. uhttps://facades.lbl.gov/publications/fundamental-materials-issues-involved01040nas a2200133 4500008004100000050001400041245006900055210006500124520057500189100002500764700002100789700002700810856006900837 1985 eng d aLBL-1745600aThe Effects of Skylight Parameters on Daylighting Energy Savings0 aEffects of Skylight Parameters on Daylighting Energy Savings3 a

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.

1 aArasteh, Dariush, K.1 aJohnson, Russell1 aSelkowitz, Stephen, E. uhttps://facades.lbl.gov/publications/effects-skylight-parameters01779nas a2200169 4500008004100000050001400041245006100055210006100116300001200177490000700189520124700196100002501443700002101468700002701489700002101516856007201537 1985 eng d aLBL-1745700aEnergy Performance and Savings Potentials with Skylights0 aEnergy Performance and Savings Potentials with Skylights a154-1790 v913 a

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.

1 aArasteh, Dariush, K.1 aJohnson, Russell1 aSelkowitz, Stephen, E.1 aSullivan, Robert uhttps://facades.lbl.gov/publications/energy-performance-and-savings01348nas a2200145 4500008004100000050001400041245005600055210005600111260003200167520086300199100002501062700002101087700002101108856007301129 1984 eng d aLBL-1747600aSkylight Energy Performance and Design Optimization0 aSkylight Energy Performance and Design Optimization aGothenburg, Swedenc06/19843 a

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.

1 aArasteh, Dariush, K.1 aJohnson, Russell1 aSullivan, Robert uhttps://facades.lbl.gov/publications/skylight-energy-performance-and