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-002275nas a2200277 4500008003900000245015300039210006900192260001200261300001200273490000800285520134500293653003301638653002101671653001601692653002501708653002001733653001801753653001301771100002101784700002101805700001901826700002401845700002201869700002901891856007701920 2016 d00aBalancing daylight, glare, and energy-efficiency goals: An evaluation of exterior coplanar shading systems using complex fenestration modeling tools0 aBalancing daylight glare and energyefficiency goals An evaluatio c01/2016 a279-2980 v1123 a

Exterior shades are the most effective way to control solar load in buildings. Twelve different coplanar shades with different geometry, material properties and cut-off angles were investigated for two California climates: the moderate San Francisco Bay Area climate and a hot and dry Southern California climate. The presented results distinguish themselves from other simulation studies by a newly developed method that combines three research-grade software programs (Radiance, EnergyPlus and Window 7) to calculate heat transfer, daylight, and glare resulting from optically-complex fenestration systems more accurately. Simulations were run for a case with constant electric lighting and a case with daylighting controls for a prototypical, internal load dominated office building.

In the case of daylighting controls, the choice of slat angle and solar cut-off angle of a fixed exterior slat shading system is non trivial. An optimum slat angle was identified for the considered cases. Material properties (e.g., solar and visible reflectance) did not affect energy use if constant electric lighting was assumed, but they did have a significant influence on energy use intensity (EUI) when daylighting controls were assumed. Energy use increased substantially when an additional interior shade was used for glare control.

10aComplex fenestration systems10aDiscomfort Glare10aEnergy Plus10aEnergy Use Intensity10aExterior shades10aGlare Control10aradiance1 aHoffmann, Sabine1 aLee, Eleanor, S.1 aMcNeil, Andrew1 aFernandes, Luis, L.1 aVidanovic, Dragan1 aThanachareonkit, Anothai uhttps://facades.lbl.gov/publications/balancing-daylight-glare-and-energy00763nas a2200205 4500008003900000245011500039210006900154260003100223653002400254653003300278653002400311653002100335653002500356653001300381100002100394700001900415700002100434700002300455856007900478 2015 d00aDiscomfort glare with complex fenestration systems and the impact on energy use when using daylighting control0 aDiscomfort glare with complex fenestration systems and the impac aBern, Switzerlandc11/201510abuilding simulation10aComplex fenestration systems10adaylighting control10aDiscomfort Glare10aEnergy Use Intensity10aradiance1 aHoffmann, Sabine1 aMcNeil, Andrew1 aLee, Eleanor, S.1 aKalyanam, Raghuram uhttps://facades.lbl.gov/publications/discomfort-glare-complex-fenestration03492nas 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-systems03205nas a2200421 4500008003900000245005700039210005600096260001200152520188100164653002202045653002502067653005202092653003702144653003302181653001602214653003302230653002002263653002102283653002002304653001802324653002502342653003002367653002202397653001202419653002902431653002302460653001902483653002402502653002502526100002102551700002202572700002402594700002102618700001902639700002902658700002202687856007402709 2014 d00aHigh Performance Building Façade Solutions-Phase II0 aHigh Performance Building Façade SolutionsPhase II c03/20143 a

The High Performance Building Façade Solutions–Phase II project was initiated through the California Energy Commission’s Public Interest Energy Research (PIER) program in July 2010 to support industry’s development and deployment of both incremental and breakthrough façade technologies in partnership with the U.S. Department of Energy (DOE). The objective of this three-year project was to develop, or support the development and deployment of, promising near-term and emerging zero net energy building façade technologies for solar control and daylighting, addressing two of the largest end uses in California commercial buildings: cooling and lighting. In partnership with industry (such as manufacturers), three classes of technologies were investigated: daylighting systems, angular-selective shading systems, and dynamic façade systems. Commercially available and emerging prototype technologies were developed and evaluated using laboratory tests. Simulations, full-scale outdoor tests in the Advanced Window Testbed, and demonstration projects quantified energy and peak electric demand reductions and occupant satisfaction, acceptance, and comfort associated with the resultant indoor environment. Several new technologies were developed using virtual prototyping tools. Integrated control systems were developed using model predictive controls. Simulation tools were developed to model operable complex fenestration systems such as shades and microprismatic films. A schematic design tool called COMFEN was developed to facilitate evaluation of these advanced technologies in the early design phase. All three classes of technologies resulted in significant reductions in perimeter zone energy use and peak electric demand, providing viable options that can support California’s long-term goal of achieving zero net energy use in the next decade.

10aautomated shading10abetween-pane shading10abidirectional scattering distribution functions10abuilding energy simulation tools10aComplex fenestration systems10adaylighting10adaylighting simulation tools10aelectrochromics10aexterior shading10agoniophotometer10alight shelves10amicroprismatic films10amodel predictive controls10amotorized shading10ashading10asolar-optical properties10aswitchable windows10athermochromics10avirtual prototyping10awindow heat transfer1 aLee, Eleanor, S.1 aCoffey, Brian, E.1 aFernandes, Luis, L.1 aHoffmann, Sabine1 aMcNeil, Andrew1 aThanachareonkit, Anothai1 aWard, Gregory, J. uhttps://facades.lbl.gov/publications/high-performance-building-fa-ade07924nas a2200265 4500008003900000245004800039210004800087260006500135520707300200653002507273653001607298653003807314653002107352653001507373653002207388653002507410653002107435653002007456653001907476100001907495700002207514700002107536700002707557856007407584 2014 d00aHigh Performance Building Mockup in FLEXLAB0 aHigh Performance Building Mockup in FLEXLAB aBerkeley, CAbLawrence Berkeley National Laboratoryc12/20143 a

Genentech has ambitious energy and indoor environmental quality performance goals for Building 35 (B35) being constructed by Webcor at the South San Francisco campus. Genentech and Webcor contracted with the Lawrence Berkeley National Laboratory (LBNL) to test building systems including lighting, lighting controls, shade fabric, and automated shading controls in LBNL's new FLEXLAB facility. The goal of the testing is to ensure that the systems installed in the new office building will function in a way that reduces energy consumption and provides a comfortable work environment for employees.

LBNL tested three facades of the new office building in the rotating FLEXLAB testbed: west, south and east. External shading, lighting, and internal shading control was configured for each orientation to replicate the conditions of B35. The three facades were each tested for one week three times between July and October 2014. Changes were made between each test to improve the performance of the systems.

Linear pendant LED light fixtures will illuminate the open office areas of the office building. These fixtures were installed in FLEXLAB. The wide spacing between rows of light fixtures results in a low lighting power density of 0.57 W/ft2 in the open office areas, while still meeting the average illuminance criteria of 300 lux (28 footcandles). A combination of the wide spacing and optics of the light fixture creates a nonuniform lighting pattern on the ceiling of the space. Changing to a diffuse lens on the uplight will help reduce abrupt changes in luminance on the ceiling but non-uniformity will persist due to the wide spacing.

The pendant light fixtures allow separate control of the downward and upward light. The lighting control design aims to enhance the quality of space by dimming upward light unison providing uniform patterns of electric light on the ceiling. The downward light of each fixture dims to provide just enough light to meet illuminance criteria below the fixture.

Webcor installed two lighting control systems manufactured by Enlighted and Encelium for testing in FLEXLAB. The Encelium system uses an open loop control architecture with a ceiling-mounted photosensor at each facade (inside of the automated shade). While there is greater variation in workplane illuminance provided by the Encelium system, the system is better able to control upward versus downward lighting and is able to control the lighting according to the lighting design intent. The architecture of the Encelium system offers more functional flexibility by allowing any input (sensors, switches etc.) or multiple inputs to affect any fixture.

The Enlighted control system uses closed loop architecture with two photosensors per fixture (one for upward light and one for downward light). The Enlighted system controlled the lights more precisely than the Encelium system to meet workplane illuminance requirements, however the upward versus downward light control did not behave according to the lighting design intent.

MechoSystems provided motorized window shades and automated control. The shades in each window had a different color fabric, one dark grey and one medium grey. Both shade fabrics were an open weave with 3% openness. Genentech selected the dark colored shade because it provides a better view of the exterior compared to the lighter colored shade. Anecdotal evidence suggests that some occupants may experience direct glare with 3% open fabric while other occupants will not experience glare under the same conditions. Visual discomfort during the worst case sunny winter condition was not evaluated. However, the east-facing orientation during the equinox period was exposed to low sun angles in the third test period so findings of just acceptable visual discomfort are expected to be similar to what might be experienced during the winter.

The shades operated as expected on sunny days (which was the predominant condition during the test period). The testing identified substantial potential energy savings for the lighting systems by stopping the shade above the sill, preventing the shade from completely covering the window and allowing the sun to shine deeper into the space through the bottom few inches of the window. On partly cloudy days, which occurred more frequently after our testing concluded, anecdotal evidence suggests that the shades could be raised more often. LBNL suggests that a second threshold be implemented which drops the shade partway to prevent direct glare from bright sun, but doesn't close the shade down to the height required to limit sunshine depth.

Thermal comfort analysis suggests that occupants seated near the shaded window will be comfortable around 80% of the time. The 20% of time where the observed conditions fall outside the ASHRAE Standard 55 are almost always due to occupants being cold in the morning. This discomfort is mostly driven by cold surrounding surfaces causing a low mean radiant temperature and overcooling from outside air during economizer mode. Only one thermal comfort station, located near the facade, was used for the experiment. Thermal comfort further from the facade is unknown but is likely to be better due to the increased distance from the relatively cold facade.

Visual comfort studies indicated that occupants could sit as close as 3.5 feet to the east and west facade and 2.5 feet to the south facade when facing parallel to the window. Occupants must sit further away from the window to be comfortable when facing the window directly. Occupants should be 3.5 feet away when facing the south facade, 4.5 feet away when facing the west facade and 5.5 feet away when facing the east facade. Thermal comfort studies show that sitting within 30 inches of the facade has a negligible effect on comfort ratings.

Daylighting controls reduced lighting energy use in FLEXLAB by 46% for east facade, 34% for south facade and 35% for west facade over 30 feet deep perimeter zone between 7 AM and 7 PM local time at autumn equinox. Occupancy controls will further reduce lighting energy use, though they were not implemented for the test due to the cell being tested unoccupied.

Genentech, Webcor, and the architectural and engineering team had access to the FLEXLAB during and for a month following the test period to observe, work, and discuss operational issues with employees and staff. The project team made their own qualitative observations about the space in terms of view, adequacy of lighting and daylight levels, color, furniture placement, etc. The project team worked collaboratively with the LBNL team to fine tune details of component design, control settings, troubleshooting, and operations. Because Genentech is introducing a new model for their work environment, a non-assigned workplace, there were detailed discussions on how to educate the occupants about the new technologies and their operational modes. Commissioning and tuning procedures were also discussed.

10acommercial buildings10adaylighting10aenergy management control systems10aexterior shading10afield test10alighting controls10amonitored evaluation10ashading controls10athermal comfort10avisual comfort1 aMcNeil, Andrew1 aKohler, Christian1 aLee, Eleanor, S.1 aSelkowitz, Stephen, E. uhttps://facades.lbl.gov/publications/high-performance-building-mockup02421nas a2200205 4500008003900000245011400039210006900153260001200222300001200234490000700246520171800253653003101971653001602002653002902018100002402047700002102071700002902092700001902121856007502140 2014 d00aMonitored lighting energy savings from dimmable lighting controls in The New York Times Headquarters Building0 aMonitored lighting energy savings from dimmable lighting control c01/2014 a498-5140 v683 a

Digital addressable, dimmable lighting controls were introduced to the US market in the early 2000s with the promise of facilitating capture of potential energy savings with greater flexibility over their historic, typically unreliable, analog counterpart. The New York Times Company installed this emerging technology, after having tested the system thoroughly prior to procurement, in their new building in New York, New York. Four years after full occupancy in 2007, the owner agreed to participate in a post-occupancy monitored evaluation of the dimmable lighting system to verify actual performance in the field. Annual lighting energy savings from daylighting, setpoint tuning and occupancy controls were determined for the daylit, open-plan office areas on three typical floors (6, 11, and 20th floors) of the 51-story high-rise tower. Energy savings were calculated from ballast control signal and occupancy data recorded by the manufacturer's lighting control system. The ballast data were calibrated with independent measurements of lighting energy consumption. Savings from dimming controls (daylighting and setpoint tuning) were 12.6 kWh/m2-yr (1.17 kWh/ft2-yr) for the daylit spaces on the three floors overall, or 20%, relative to ASHRAE 90.1-2007. Compared to the prescriptive code in effect at the time of the building's construction (ASHRAE 90.1-2001), savings were 21.0 kWh/m2-yr (1.95 kWh/ft2-yr) or 28%. Annual lighting energy use with all lighting control strategies was 33.9 kWh/m2-yr (3.15 kWh/ft2-yr) in the daylit, open plan zones on average for the three floors. A simple payback analysis was conducted.

10aBuilding energy-efficiency10adaylighting10alighting control systems1 aFernandes, Luis, L.1 aLee, Eleanor, S.1 aDiBartolomeo, Dennis, L.1 aMcNeil, Andrew uhttps://facades.lbl.gov/publications/monitored-lighting-energy-savings01785nas a2200193 4500008003900000245016500039210006900204520103800273653002701311653002901338653003801367653001101405653002301416100001601439700001901455700002001474700002101494856007601515 2013 d00aAcceleration of the matrix multiplication of Radiance three phase daylighting simulations with parallel computing on heterogeneous hardware of personal computer0 aAcceleration of the matrix multiplication of Radiance three phas3 a

Building designers are increasingly relying on complex fenestration systems to reduce energy consumed for lighting and HVAC in low energy buildings. Radiance, a lighting simulation program, has been used to conduct daylighting simulations for complex fenestration systems. Depending on the configurations, the simulation can take hours or even days using a personal computer. This paper describes how to accelerate the matrix multiplication portion of a Radiance three-phase daylight simulation by conducting parallel computing on heterogeneous hardware of a personal computer. The algorithm was optimized and the computational part was implemented in parallel using OpenCL. The speed of new approach was evaluated using various daylighting simulation cases on a multicore central processing unit and a graphics processing unit. Based on the measurements and analysis of the time usage for the Radiance daylighting simulation, further speedups can be achieved by using fast I/O devices and storing the data in a binary format.

10adaylighting simulation10agraphics processing unit10amulticore central processing unit10aOpenCL10aparallel computing1 aZuo, Wangda1 aMcNeil, Andrew1 aWetter, Michael1 aLee, Eleanor, S. uhttps://facades.lbl.gov/publications/acceleration-matrix-multiplication02440nas a2200157 4500008003900000245011900039210006900158520181800227653005202045653003202097653001602129653002502145100001902170700002102189856007202210 2013 d00aAnnual daylighting performance of a passive optical light shelf in sidelit perimeter zones of commercial buildings0 aAnnual daylighting performance of a passive optical light shelf 3 a

Sunlight redirecting systems have the potential to significantly offset electric lighting energy use in deep perimeter zones of buildings where the windows are subject to high daylight availability. New Radiance modeling tools have recently been developed and validated, enabling accurate and timely simulation analysis of the annual energy and comfort performance of these optically-complex, anisotropic systems. A parametric study was conducted using these tools to evaluate the performance of a commercially-available passive optical light shelf (OLS) in a 17.4 m deep (57 ft), south-facing open plan office zone in three climates. Daylighting efficiency, discomfort glare, and lighting energy savings with continuous dimming and bi-level switching controls were determined at varying depths within the zone. The OLS decreased lighting energy use significantly throughout the depth of the space and achieved these savings with minimal discomfort glare in the area near the window. Annual lighting energy use intensity was reduced to 1.71-1.82 kWh/ft2-yr (22-27%) over the full depth of the perimeter zone across the three climates modeled (Phoenix, Washington DC, and Minneapolis) compared to a non-daylit zone at 2.34 kWh/ft2-yr. There was a greater occurrence of discomfort glare (3-7% during daytime work hours) if the occupant was in a seated view position looking at the window from the back of the room. The system is passive, needing no adjustment during the day and over the seasons and can be used as a retrofit measure in existing buildings. These results are encouraging and demonstrate how the primary daylit sidelit area can be extended well beyond the defined limits provided by the newly adopted ASHRAE 90.1-2010 code (i.e., 1.0 times the head height of the window).

10abidirectional scattering distribution functions10abuildings energy efficiency10adaylighting10aRadiance simulations1 aMcNeil, Andrew1 aLee, Eleanor, S. uhttps://facades.lbl.gov/publications/annual-daylighting-performance00580nas a2200133 4500008003900000245015800039210006900197260001200266100002200278700001900300700003100319700002100350856007500371 2013 d00aAutomated Production of Optimization-Based Control Logics for Dynamic Façade Systems, with Experimental Application to Two-Zone External Venetian Blinds0 aAutomated Production of OptimizationBased Control Logics for Dyn c09/20131 aCoffey, Brian, E.1 aMcNeil, Andrew1 aNouidui, Thierry, Stephane1 aLee, Eleanor, S. uhttps://facades.lbl.gov/publications/automated-production-optimization00649nas a2200109 4500008004100000245007100041210006900112260001200181520026300193100001900456856006400475 2013 eng d00aBSDFViewer: A utility for interactive exploration of BSDF datasets0 aBSDFViewer A utility for interactive exploration of BSDF dataset c09/20133 a

BSDFViewer is a utility for interactive exploration of BSDF datasets. With BSDF view you can load a BSDF xml file and view the outgoing distribution for user-selectable incident directions. You can look at transmission or reflection for front or back.

1 aMcNeil, Andrew uhttp://www.radiance-online.org/download-install/bsdf-viewer01223nas 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-microstructured02991nas a2200217 4500008003900000245010400039210006900143260004200212300001000254490000700264520225800271653003202529653001602561653002402577653001902601653001202620100002902632700002102661700001902682856007202701 2013 d00aEmpirical Assessment of a Prismatic Daylight-Redirecting Window Film in a Full-Scale Office Testbed0 aEmpirical Assessment of a Prismatic DaylightRedirecting Window F aHuntington Beach, Californiac10/2013 a19-450 v103 a

Daylight redirecting systems with vertical windows have the potential to offset lighting energy use in deep perimeter zones. Microstructured prismatic window films can be manufactured using low-cost, roll-to-roll fabrication methods and adhered to the inside surface of existing windows as a retrofit measure or installed as a replacement insulating glass unit in the clerestory portion of the window wall. A clear film patterned with linear, 50-250 micrometer high, four-sided asymmetrical prisms was fabricated and installed in the south-facing, clerestory low-e, clear glazed windows of a full-scale testbed facility. Views through the film were distorted. The film was evaluated in a sunny climate over a two-year period to gauge daylighting and visual comfort performance. The daylighting aperture was small (window-to-wall ratio of 0.18) and the lower windows were blocked off to isolate the evaluation to the window film. Workplane illuminance measurements were made in the 4.6 m (15 ft) deep room furnished as a private office. Analysis of discomfort glare was conducted using high dynamic range imaging coupled with the evalglare software tool, which computes the daylight glare= probability and other metrics used to evaluate visual discomfort.

The window film was found to result in perceptible levels of discomfort glare on clear sunny days from the most conservative view point in the rear of the room looking toward the window. Daylight illuminance levels at the rear of the room were significantly increased above the reference window condition, which was defined as the same glazed clerestory window but with an interior Venetian blind (slat angle set to the cut-off angle), for the equinox to winter solstice period on clear sunny days. For partly cloudy and overcast sky conditions, daylight levels were improved slightly. To reduce glare, the daylighting film was coupled with a diffusing film in an insulating glazing unit. The diffusing film retained the directionality of the redirected light= spreading it within a small range of outgoing angles. This solution was found to reduce glare to imperceptible levels while retaining for the most part the illuminance levels achieved solely by the daylighting film.

10abuildings energy efficiency10adaylighting10amicrostructure film10aprismatic film10awindows1 aThanachareonkit, Anothai1 aLee, Eleanor, S.1 aMcNeil, Andrew uhttps://facades.lbl.gov/publications/empirical-assessment-prismatic00864nas a2200109 4500008003900000245007600039210006900115260001200184520046100196100001900657856007800676 2013 d00aThe Five-Phase Method for Simulating Complex Fenestration with Radiance0 aFivePhase Method for Simulating Complex Fenestration with Radian c09/20133 a

The "five-phase method" is an extension of the three-phase method that more closely follows the standard daylight coefficient model for dynamic daylight simulations proposed by Bourgeois et al (2008). More specifically, the five-phase method handles the direct solar component separately from the sky and interreflected solar component to achieve better accuracy of the distribution of direct solar light in a room for complex glazing systems (CFS).

1 aMcNeil, Andrew uhttps://facades.lbl.gov/publications/five-phase-method-simulating-complex01789nas a2200217 4500008003900000245015800039210006900197260006500266520094400331100002101275700002401296700002201320700001901342700002201361700002401383700002101407700002701428700002301455700001601478856007701494 2013 d00aA Post-Occupancy Monitored Evaluation of the Dimmable Lighting, Automated Shading, and Underfloor Air Distribution System in The New York Times Building0 aPostOccupancy Monitored Evaluation of the Dimmable Lighting Auto aBerkeley, CAbLawrence Berkeley National Laboratoryc01/20133 a

With aggressive goals to reduce national energy use and carbon emissions, the US Department of Energy will be looking to exemplary buildings that have already invested in new approaches to achieving the energy performance goals now needed at a national level. The New York Times Building, in New York, New York, incorporates a number of innovative technologies, systems and processes and could become a model for widespread replication in new and existing buildings. Post-occupancy data are invaluable in establishing confidence in innovation. A year-long monitored study was conducted to verify energy performance, assess occupant comfort and satisfaction with the indoor environment, and evaluate impacts on maintenance and operations. Lessons learned were derived from the analysis; these lessons could help identify and shape policy, financial, or supporting strategies to accelerate diffusion in the commercial building market.

1 aLee, Eleanor, S.1 aFernandes, Luis, L.1 aCoffey, Brian, E.1 aMcNeil, Andrew1 aClear, Robert, D.1 aWebster, Thomas, L.1 aBauman, Fred, S.1 aDickerhoff, Darryl, J.1 aHeinzerling, David1 aHoyt, Tyler uhttps://facades.lbl.gov/publications/post-occupancy-monitored-evaluation00448nas a2200109 4500008003900000245010200039210006900141260001200210100001900222700002100241856007600262 2013 d00aSimulated daylight performance of a new prototype prismatic window film in deep open plan offices0 aSimulated daylight performance of a new prototype prismatic wind c09/20131 aMcNeil, Andrew1 aLee, Eleanor, S. uhttps://facades.lbl.gov/publications/simulated-daylight-performance-new01617nas a2200109 4500008004100000245007700041210006900118260001200187520121000199100001901409856007901428 2013 eng d00aThe three-phase method for simulating complex fenestration with Radiance0 athreephase method for simulating complex fenestration with Radia c08/20133 a

The "three-phase method" is a means to perform annual simulation of complex and/or dynamic fenestration systems. Flux transfer is broken into the following three phases for independ ent simulation:

  1. Sky to exterior of fenestration
  2. Transmission through fenestration
  3. Interior of fenestration into the simulated space

Rather than simulate a specific daylight condition, the three-phase method calculates normalized coefficients that relate flux input to output for each phase. A result for a specific daylight condition is computed by multiplying the coefficient matrices by the input values (sky luminance values). Matrix calculation can be performed very quickly enabling the user to simulate many sky conditions and fenestration transmission properties.

This document starts with a brief overview of the three-phase method. Following is a detailed discussion of each phase of flux transfer including an explanation of new tools that were develop ed for the three - phase method, explained in detail. Two examples follow the detailed discussion, the first a simple space with one south facing window, the second a space with south and east facing windows.

1 aMcNeil, Andrew uhttps://facades.lbl.gov/publications/three-phase-method-simulating-complex02476nas a2200325 4500008003900000245007600039210006900115260001200184300001200196490000700208520149100215653001701706653001601723653004601739653002201785653001001807653003301817653001301850653001201863100001901875700002301894700001901917700002201936700002801958700002101986700002102007700002102028700002402049856007702073 2013 d00aU.S. energy savings potential from dynamic daylighting control glazings0 aUS energy savings potential from dynamic daylighting control gla c11/2013 a415-4230 v663 a

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

10aClerestories10adaylighting10aDynamic prismatic optical elements (dPOE)10aenergy efficiency10aGlare10aindoor environmental quality10aradiance10awindows1 aShehabi, Arman1 aDeForest, Nicholas1 aMcNeil, Andrew1 aMasanet, Eric, R.1 aGreenblatt, Jeffery, B.1 aLee, Eleanor, S.1 aMasson, Georgeta1 aHelms, Brett, A.1 aMilliron, Delia, J. uhttps://facades.lbl.gov/publications/us-energy-savings-potential-dynamic02197nas 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-used00787nas a2200133 4500008003900000245009500039210006900134260001200203300000600215520032200221100001900543700002100562856007000583 2012 d00aOn the benefits of a variable-resolution bidirectional scattering distribution data format0 abenefits of a variableresolution bidirectional scattering distri c09/2012 a53 a

This summary report adds context to the recent development of a new format for variable-resolution bi-directional scattering data. Specifically we discuss why a high resolution BSDF format is needed, the advantages of a variable resolution data format, and the new capabilities that stem from this development.

1 aMcNeil, Andrew1 aLee, Eleanor, S. uhttps://facades.lbl.gov/publications/benefits-variable-resolution01397nas a2200145 4500008004100000245013200041210006900173260001200242300000700254520084000261100003101101700001901132700002101151856007901172 2012 eng d00aDevelopment of a simulation-based controls framework for implementation of controls algorithms for complex fenestration systems0 aDevelopment of a simulationbased controls framework for implemen c09/2012 a153 a

Effectively controlled dynamic windows can substantially reduce the energy consumption of buildings. Unfortunately, modular and extensible frameworks for testing and evaluating window system control algorithms that include the effects of thermal mass are missing in the research community.

This paper describes a modular and extensible simulation-based framework that uses different simulation tools such as EnergyPlus, Modelica, Radiance, and the Building Controls Virtual Test Bed (BCVTB) to develop and evaluate the performance of integrated façade control strategies. We present a simulation framework and a proof-of concept application using the framework to control a venetian blind in a physical test cell in order to reduce its zone thermal load based on solar inputs and internal gains measured at the test cell.

1 aNouidui, Thierry, Stephane1 aMcNeil, Andrew1 aLee, Eleanor, S. uhttps://facades.lbl.gov/publications/development-simulation-based-controls02762nas a2200205 4500008004100000245009100041210006900132260001200201520206000213100002102273700002402294700002802318700002102346700002402367700002102391700002102412700001902433700002702452856007702479 2012 eng d00aElectro-Responsive Polymer Glazings For Smart Windows With Dynamic Daylighting Control0 aElectroResponsive Polymer Glazings For Smart Windows With Dynami c02/20123 a

In the context of alarming phenomenon of global warming with harmful consequences such as increased green house gases beyond predictions, the development of advanced energy efficient technologies became of a primary importance. Since the building sector accounts for 39% of total US primary energy consumption, fenestration can significantly contribute to lowering the energy use for heating, cooling, and lighting. An estimated 9% reduction in total US building energy use, or 3.47 Q, could be attained by dynamic solar/thermal control and daylighting if these advanced optical technologies were adopted throughout the residential and commercial building sectors. In spite of the great research and engineering efforts in the fast growing area of smart windows, development of glazing devices able to provide efficient, durable, and inexpensive products for dynamic daylight control is in infancy. Like the electrochromic glazings now emerging on the market, microscale, switchable daylight-redirecting glazings have the potential for widespread application if a low-cost, durable coating can be engineered and manufactured with the proper set of attributes.

Here we report on the development of a new technology using smart materials for switchable daylight-redirecting glazings. The proposed system consists in a prismatic optical element (POE) fabricated by micro-imprinting of an elastic redox-active polymer network capable to change its geometry and thereby its optical properties in response to an external stimulus. It is expected that the prismatic optical element reversibly collapses in response to an applied potential, thereby modulating the fraction of light which is redirected. The fabrication of the dynamic prismatic optical element from simulation-driven design to materials synthesis and device integration will be described. Investigation of specto-electrochemical characteristics of the redox-active grating and challenges encountered with respect to electromechanical induced structural changes will be also presented.

1 aMasson, Georgeta1 aMendlesberg, Rueben1 aFernandez-Cuesta, Irene1 aCabrini, Stefano1 aMilliron, Delia, J.1 aHelms, Brett, A.1 aLee, Eleanor, S.1 aMcNeil, Andrew1 aSelkowitz, Stephen, E. uhttps://facades.lbl.gov/publications/electro-responsive-polymer-glazings01798nas a2200193 4500008003900000245013300039210006900172490000700241520111100248653003501359653003201394653001301426653001201439653001601451100002101467700001901488700002001507856007701527 2012 d00aAn Hourly-Based Performance Comparison of an Integrated Micro-Structural Perforated Shading Screen with Standard Shading Systems0 aHourlyBased Performance Comparison of an Integrated MicroStructu0 v503 a

This article evaluates the performance of an integrated micro structural perforated shading screen (MSPSS). Such a system maintains a visual connection with the outdoors while imitating the shading functionality of a venetian blind. Building energy consumption is strongly influenced by the solar gains and heat transfer through the transparent parts of the fenestration systems. MSPSS is angular-dependent shading device that provides an effective strategy in the control of daylight, solar gains and overheating through windows. The study focuses on using direct experimental methods to determine bi-directional transmittance properties of shading systems that are not included as standard shading options in readily available building performance simulation tools. The impact on the indoor environment, particularly temperature and daylight were investigated and compared to three other static complex fenestration systems. The bi-directional description of the systems was used throughout the article. The simulations were validated against outdoor measurements of solar and light transmittance.

10abuilding performance modelling10acomplex fenestration system10adaylight10ashading10asolar gains1 aAppelfeld, David1 aMcNeil, Andrew1 aSvendsen, Svend uhttps://facades.lbl.gov/publications/hourly-based-performance-comparison00422nas a2200109 4500008004100000245007600041210006900117260001200186100001900198700002100217856007400238 2012 eng d00aUsing Radiance and GenOpt to design static daylight redirection systems0 aUsing Radiance and GenOpt to design static daylight redirection  c09/20121 aMcNeil, Andrew1 aLee, Eleanor, S. uhttps://facades.lbl.gov/publications/using-radiance-and-genopt-design00704nas a2200181 4500008003900000245014600039210006900185260001200254490001500266653005200281653003200333653001600365653001300381653001500394100001900409700002100428856007300449 2012 d00aA validation of the Radiance three-phase simulation method for modeling annual daylight performance of optically-complex fenestration systems0 avalidation of the Radiance threephase simulation method for mode c05/20120 vApril 201210abidirectional scattering distribution functions10abuildings energy efficiency10adaylighting10aradiance10avalidation1 aMcNeil, Andrew1 aLee, Eleanor, S. uhttps://facades.lbl.gov/publications/validation-radiance-three-phase01204nas a2200157 4500008004100000245009300041210006900134260003100203300001500234520064900249100001600898700001900914700002000933700002100953856007200974 2011 eng d00aAcceleration of Radiance for Lighting Simulation by using Parallel Computing with OpenCL0 aAcceleration of Radiance for Lighting Simulation by using Parall aSydney, Australiac11/2011 ap. 110-1173 a

This study attempted to accelerate annual daylighting simulations for fenestration systems in Radiance ray-tracing program. The algorithm was optimized to reduce both the redundant data input/output operations and floating-point operations. To further accelerate the simulation speed, calculation for matrices multiplications was implemented in parallel on a graphics processing unit using OpenCL, a cross-platform parallel programming language. Numerical experiments show that combination of above measures can speed up the annual daylighting simulations 101.7 times or 28.6 times when sky vector has 146 or 2306 elements, respectively.

1 aZuo, Wangda1 aMcNeil, Andrew1 aWetter, Michael1 aLee, Eleanor, S. uhttps://facades.lbl.gov/publications/acceleration-radiance-lighting02631nas a2200169 4500008004100000245009900041210007000140260002400210520201600234100002702250700002002277700002302297700002202320700001902342700002102361856007902382 2011 eng d00aCOMFEN 3.0: Evolution of an Early Design Tool for Commercial Façades and Fenestration Systems0 aCOMFEN 30 Evolution of an Early Design Tool for Commercial Façad aPomona, CAc03/20113 a

Achieving a net-zero energy building cannot be done solely by improving the efficiency of the engineering systems. It also requires consideration of the essential nature of the building including factors such as architectural form, massing, orientation and enclosure. Making informed decisions about the fundamental character of a building requires assessment of the effects of the complex interaction of these factors on the resulting performance of the building. The complexity of these interactions necessitates the use of modeling and simulation tools to dynamically analyze the effects of the relationships, yet decisions about the building fundamentals are often made in the earliest stages of design, before a 'building' exists to model.

To address these issues, Lawrence Berkeley National Laboratory (LBNL) has developed an early-design energy modeling tool (COMFEN) specifically to help make informed decisions about building façade fundamentals by considering the design of the building envelope, orientation and massing on building performance. COMFEN focuses on the concept of a "space" or "room" and uses the EnergyPlus, and Radiance™ engines and a simple, graphic user interface to allow the user to explore the effects of changing key early-design input variables on energy consumption, peak energy demand, and thermal and visual comfort. Comparative results are rapidly presented in a variety of graphic and tabular formats to help users move toward optimal façade and fenestration design choices.

While COMFEN 1.0 utilized an Excel™–based user interface, COMFEN 3.0 has been reworked to include a simple, more intuitive, yet powerful Graphic User Interface (GUI), a broader range of libraries for associated system and component choices and deliver a wider range of graphic outputs and options.

This paper (and presentation) outlines the objectives in developing and further refining COMFEN, the mechanics of the program, and plans for future development. 

1 aSelkowitz, Stephen, E.1 aMitchell, Robin1 aMcClintock, Maurya1 aMcQuillen, Daniel1 aMcNeil, Andrew1 aYazdanian, Mehry uhttps://facades.lbl.gov/publications/comfen-30-evolution-early-design-tool00572nas a2200145 4500008003900000245011600039210006900155260001200224100003100236700001900267700002200286700002200308700002100330856007500351 2011 d00aModeling solar heat gains of complex fenestration systems using bidirectional scattering distribution functions0 aModeling solar heat gains of complex fenestration systems using  c09/20111 aNouidui, Thierry, Stephane1 aMcNeil, Andrew1 aKohler, Christian1 aCoffey, Brian, E.1 aLee, Eleanor, S. uhttps://facades.lbl.gov/publications/modeling-solar-heat-gains-complex01669nas a2200121 4500008004100000245015500041210006900196260001200265300000700277520117000284100001901454856007401473 2011 eng d00aOn the sensitivity of daylight simulations to the resolution of the hemispherical basis used to define bidirectional scattering distribution functions0 asensitivity of daylight simulations to the resolution of the hem c09/2011 a193 a

The Radiance simulation program includes new tools that enable daylight modeling of complex fenestration systems (CFS) using bi-directional transmission distribution functions (BTDF). The tools use the Klems angle basis to define the number of paired incoming and outgoing data values. However, the Klems angle basis was developed for thermal simulations and may be too low of a resolution for some types of daylight systems, particularly those that exhibit peaky, specular transmission. This study evaluates the sensitivity of the angle basis resolution by comparing simulation results for the Klems angle basis against results using two higher resolution angle bases. The first evaluation compares results for specific points in time. The second evaluation compares simulation results using annual performance metrics. Annual lighting energy data were found to agree to within 1%. Annual assessments of discomfort glare were found to disagree by 7% because high resolution basis resolved glare sources into smaller, more intense sources. We concluded that high resolution bases are appropriate for specific types of CFS and performance metrics.

1 aMcNeil, Andrew uhttps://facades.lbl.gov/publications/sensitivity-daylight-simulations01571nas 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-performance