02275nas 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-fenestration02296nas a2200121 4500008003900000245011100039210006900150260003500219520180300254100002102057700002102078856007502099 2015 d00aPotential energy savings with exterior shades in large office buildings and the impact of discomfort glare0 aPotential energy savings with exterior shades in large office bu aKansas City, Missouric04/20153 a

Exterior shades are highly efficient for reducing solar load in commercial buildings. Their impact on net energy use depends on the annual energy balance of heating, cooling, fan and lighting energy. This paper discusses the overall energy use intensity of various external shading systems for a prototypical large office building split into the different types of energy use and for different orientations and window sizes. Lighting energy was calculated for a constant lighting power as well as for dimmed lighting fixtures (daylighting control).

In Section 3, slat angles and solar cut-off angles were varied for fixed exterior slat shading systems. While the most light-blocking shades performed best for the case without daylighting controls, the optimum cut-off angle with daylighting controls was found to be 30 deg for the office building prototype used in Chicago and Houston. For large window-to-wall (WWR) ratios, window related annual energy use could be reduced by at least 70 % without daylighting control and by a minimum of 86 % with daylighting control in average over all orientations.

The occurrence of discomfort glare was is considered in Section 4 of the paper, which looks at the performance of commercially available exterior shading systems when an interior shade is used in addition to the exterior shade during hours when occupants would experience discomfort glare. Glare control impacts overall energy use intensity significantly for exterior shades with high transmittance, especially when daylighting controls are used. In these cases, exterior shades are only beneficial for window-to-wall areas ≥ 45% in the hot Houston climate. For smaller windows and in a heating/cooling climate like Chicago, exterior shades can increase energy consumption.

1 aHoffmann, Sabine1 aLee, Eleanor, S. uhttps://facades.lbl.gov/publications/potential-energy-savings-exterior03492nas 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-ade02354nas a2200229 4500008003900000245013200039210006900171260001200240300001000252490000800262520159100270653003201861653001801893653001801911653001201929100002101941700001801962700002101980700001802001700002902019856007602048 2013 d00aAn empirical study of a full-scale polymer thermochromic window and its implications on material science development objectives0 aempirical study of a fullscale polymer thermochromic window and  c09/2013 a14-260 v1163 a

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

10abuildings energy efficiency10aSolar control10aThermochromic10awindows1 aLee, Eleanor, S.1 aPang, Xiufeng1 aHoffmann, Sabine1 aGoudey, Howdy1 aThanachareonkit, Anothai uhttps://facades.lbl.gov/publications/empirical-study-full-scale-polymer02423nas 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/187967