02126nas a2200169 4500008004100000050001500041245006600056210006600122260003400188520154400222100002101766700002501787700002101812700002301833700002701856856007301883 1998 eng d aLBNL-4169400aEnergy and Daylight Performance of Angular Selective Glazings0 aEnergy and Daylight Performance of Angular Selective Glazings aClearwater Beach, FLc12/19983 a

This paper presents the results of a study investigating the energy and daylight performance of anisotropic angular selective glazings. The DOE-2.1E energy simulation program was used to determine the annual cooling, lighting and total electricity use, and peak electric demand. RADIANCE, a lighting simulation program, was used to determine daylight illuminance levels and distribution. We simulated a prototypical commercial office building module located in Blythe, California. We chose three hypothetical conventional windows for comparison: a single-pane tinted window, a double-pane low-E window, and a double-pane spectrally selective window. Daylighting controls were used. No interior shades were modeled in order to isolate the energy effects of the angular selective glazing. Our results show that the energy performance of the prototype angular selective windows is about the same as conventional windows for a 9.14 m (30 ft) deep south-facing perimeter zone with a large-area window in the hot, sunny climate of Blythe. It is theoretically possible to tune the angular selectivity of the glazing to achieve annual cooling energy reductions of 18%, total electricity use reductions of 15%, and peak electric demand reductions of 11% when compared to a conventional glazing with the same solar-optical properties at normal incidence. Angular selective glazings can provide more uniformly distributed daylight, particularly in the area next to the window, which will result in a more visually comfortable work environment.

1 aSullivan, Robert1 aBeltran, Liliana, O.1 aLee, Eleanor, S.1 aRubin, Michael, D.1 aSelkowitz, Stephen, E. uhttps://facades.lbl.gov/publications/energy-and-daylight-performance03351nas a2200169 4500008004100000050001500041245006800056210006800124260002400192300001200216490001600228520278700244100002103031700002303052700002703075856007903102 1996 eng d aLBNL-3990500aEnergy Performance Analysis of Prototype Electrochromic Windows0 aEnergy Performance Analysis of Prototype Electrochromic Windows aBoston, MAc07/1997 a149-1560 v103, Part 23 a

This paper presents the results of a study investigating the energy performance of three newly developed prototype electrochromic devices. The DOE-2.1E energy simulation program was used to analyze the annual cooling, lighting, and total electric energy use and peak demand as a function of window type and size. We simulated a prototypical commercial office building module located in the cooling-dominated locations of Phoenix, AZ and Miami, FL. Heating energy use was also studied in the heating-dominated location of Madison, WI. Daylight illuminance was used to control electrochromic state-switching. Two types of window systems were analyzed; i.e., the outer pane electrochromic glazing was combined with either a conventional low-E or a spectrally selective inner pane. The properties of the electrochromic glazings are based on measured data of new prototypes developed as part of a cooperative DOE-industry program.

Our results show the largest difference in annual electric energy performance between the different window types occurs in Phoenix and is about 6.5 kWh/m2 floor area (0.60 kWh/ft2) which can represent a cost of about $.52/m2 ($.05/ft2) using electricity costing $.08/kWh. Much larger differences exist when electrochromic windows are compared to conventional glazings in use today. At large window sizes, such energy savings can be as large as 90 kWh/m2 (8.4 kWh/ft2). Specific electrochromic performance varies with window-to-wall area ratio; i.e., at low ratios, one type electrochromic performs best, while at large ratios, another type performs best. In general, an electrochromic glazing combined with a spectrally selective glazings is better than one combined with a low-E glazing; however, at low-window-to-wall area ratios, this situation reverses slightly. There is almost no difference in peak electric demand for the different electrochromic windows analyzed.

In heating-dominated locations, the electrochromic should be maintained in its bleached state during the heating season to take advantage of beneficial solar heat gain which would reduce the amount of required heating. This also means that the electrochromic window with the largest solar heat gain coefficient is best. The largest heating energy performance difference in Madison for the various window types is 43 MJ/m2 floor area (4.0 kBtu/ft2). This represents a cost of about $.26/m2 floor area ($.024/ft2) using gas costing $0.60/therm ($5.69/GJ, $6.00/MBtu). However, a non-switching electrochromic will not provide desired glare control so that a control strategy that minimizes winter heating use may not be routinely desirable in many buildings.

1 aSullivan, Robert1 aRubin, Michael, D.1 aSelkowitz, Stephen, E. uhttps://facades.lbl.gov/publications/energy-performance-analysis-prototype01784nas a2200157 4500008004100000050001400041245009500055210006900150260003100219520120900250100002101459700002101480700002301501700002701524856007501551 1996 eng d aLBL-3825200aThe Energy Performance of Electrochromic Windows in Heating-Dominated Geographic Locations0 aEnergy Performance of Electrochromic Windows in HeatingDominated aFreiburg, Germanyc09/19963 a

This paper presents the results of a study investigating the energy performance of electrochromic windows in heating-dominated geographic locations under a variety of state-switching control strategies. We used the DOE-2.1E energy simulation program to analyze the annual heating, cooling and lighting energy use and performance as a function of glazing type, size, and electrochromic control strategy. We simulated a prototypical commercial office building module located in Madison, Wisconsin. Control strategies analyzed were based on daylight illuminance, incident total solar radiation, and space cooling load. Our results show that overall energy performance is best if the electrochromic is left in its clear or bleached state during the heating season, but controlled during the cooling season using daylight illuminance as a control strategy. Even in such heating dominated locations as Madison, there is still a well-defined cooling season when electrochromic switching will be beneficial. However, having the electrochromic remain in its bleached state during the winter season may result in glare and visual comfort problems for occupants much in the same way as conventional glazings.

1 aSullivan, Robert1 aLee, Eleanor, S.1 aRubin, Michael, D.1 aSelkowitz, Stephen, E. uhttps://facades.lbl.gov/publications/energy-performance-electrochromic02188nas a2200169 4500008004100000024001200041245007000053210006900123260002900192490001600221520160700237100002101844700002201865700002501887700002701912856007901939 1996 eng d aUC-160000aEnergy Performance of Evacuated Glazings in Residential Buildings0 aEnergy Performance of Evacuated Glazings in Residential Building aSan Antonio, TXc06/19960 v102, Part 23 a

This paper presents the results of a study investigating the energy performance of evacuated glazings or glazings which maintain a vacuum between two panes of glass. Their performance is measured by comparing results to prototype highly insulated superwindows as well as a more conventional insulating glass unit with a low-E coating and argon gas fill. We used the DOE-2.1E energy analysis simulation program to analyze the annual and hourly heating energy use due to the windows of a prototypical single-story house located in Madison, Wisconsin. Cooling energy performance was also investigated. Our results show that for highly insulating windows, the solar heat gain coefficient is as important as the windows U-factor in determining heating performance for window orientations facing west-south-east. For other orientations in which there is not much direct solar radiation, the windows U-factor primarily governs performance. The vacuum glazings had lower heating requirements than the superwindows for most window orientations. The conventional low-E window outperformed the superwindows for southwest-south-southeast orientations. These performance differences are directly related to the solar heat gain coefficients of the various windows analyzed. The cooling performance of the windows was inversely related to the heating performance. The low solar heat gain coefficients of the superwindows resulted in the best cooling performance. However, we were able to mitigate the cooling differences of the windows by using an interior shading device that reduced the amount of solar gain.

1 aSullivan, Robert1 aBeck, Fredric, A.1 aArasteh, Dariush, K.1 aSelkowitz, Stephen, E. uhttps://facades.lbl.gov/publications/energy-performance-evacuated-glazings02425nas a2200169 4500008004100000024001100041245009500052210006900147260003100216520180500247100002102052700002102073700003402094700002302128700002702151856007702178 1994 eng d aUC-35000aEffect of Switching Control Strategies on the Energy Performance of Electrochromic Windows0 aEffect of Switching Control Strategies on the Energy Performance aFreiburg, Germanyc04/19943 a

This paper presents the results of a study investigating the energy performance of electrochromic windows under a variety of state-switching control strategies. We used the DOE-2.1E energy simulation program to analyze the annual cooling, lighting, and total electricity use and peak demand as a function of glazing type, size, and electrochromic control strategy. We simulated a prototypical commercial office building module located in the cooling-dominated location of Blythe, California. Control strategies analyzed were based on daylight illuminance, incident total solar radiation, and space cooling load. Our results show that when a daylighting strategy is used to reduce electric lighting requirements, control algorithms based on daylight illuminance results in the best overall annual energy performance. If daylighting is not an design option, controls based on space cooling load yield the best performance through solar heat gain reduction. The performance of incident total solar radiation control strategies varies as a function of the switching setpoints; for small to moderate window sizes which result in small to moderate solar gains, a large setpoint-range was best since it provides increased illuminance for daylighting without much cooling penalty; for larger window sizes, which provide adequate daylight, a smaller setpoint-range was best to reduce unwanted solar heat gains and the consequential increased cooling requirement. Of particular importance is the fact that reduction in peak electric demand was found to be independent of the type of control strategy used for electrochromic switching. This is because the electrochromics are generally in their most colored state under peak conditions, and the mechanism used for achieving such a state is not important.

1 aSullivan, Robert1 aLee, Eleanor, S.1 aPapamichael, Konstantinos, M.1 aRubin, Michael, D.1 aSelkowitz, Stephen, E. uhttps://facades.lbl.gov/publications/effect-switching-control-strategies01779nas 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-savings