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External Shading Devicesin Commercial BuildingsThe Impact on Energy Use,Peak Demand and Glare ControlJohn Carmody and Kerry HaglundCenter for Sustainable Building ResearchUniversity of MinnesotaThe Alcoa Building in Pittsburgh, PA uses exterior shading devices.Architect: The Design Alliance Architects; Photo: Courtesy of ViraconSponsored byAir Movement and Control Association International30 West University DriveArlington Heights, IL 60004847-394-0150www.amca.org


External Shading Devices in Commercial BuildingsThe Impact on Energy Use, Peak Demand and Glare ControlJohn Carmody and Kerry HaglundCenter for Sustainable Building Reserach, University of MinnesotaContentsAcknowledgements ...........................................................2Introduction ........................................................................3Minneapolis, MinnesotaEast Orientation—Moderate Window Area ............6East Orientation—Large Window Area ...................7South Orientation—Moderate Window Area .........8South Orientation—Large Window Area ................9West Orientation—Moderate Window Area .........10West Orientation—Large Window Area ................11Houston, TexasEast Orientation—Moderate Window Area ..........24East Orientation—Large Window Area .................25South Orientation—Moderate Window Area .......26South Orientation—Large Window Area ..............27West Orientation—Moderate Window Area .........28West Orientation—Large Window Area ................29Chicago, IllinoisEast Orientation—Moderate Window Area ..........12East Orientation—Large Window Area .................13South Orientation—Moderate Window Area .......14South Orientation—Large Window Area ..............15West Orientation—Moderate Window Area .........16West Orientation—Large Window Area ................17Phoenix, ArizonaEast Orientation—Moderate Window Area ..........30East Orientation—Large Window Area .................31South Orientation—Moderate Window Area .......32South Orientation—Large Window Area ..............33West Orientation—Moderate Window Area .........34West Orientation—Large Window Area ................35Washington, DCEast Orientation—Moderate Window Area ..........18East Orientation—Large Window Area .................19South Orientation—Moderate Window Area .......20South Orientation—Large Window Area ..............21West Orientation—Moderate Window Area .........22West Orientation—Large Window Area ................23Los Angeles, CaliforniaEast Orientation—Moderate Window Area ..........36East Orientation—Large Window Area .................37South Orientation—Moderate Window Area .......38South Orientation—Large Window Area ..............39West Orientation—Moderate Window Area .........40West Orientation—Large Window Area ................41Appendix ...........................................................................42Air Movement and Control Association International (www.amca.org) Page 1


IntroductionBenefits of ExternalShading DevicesExterior shading devices such asoverhangs and vertical fins have anumber of advantages that contributeto a more sustainable building.First, exterior shading devices resultin energy savings by reducingdirect solar gain through windows.By using exterior shading deviceswith less expensive glazings, it issometimes possible to obtain performanceequivalent to unshadedhigher performance glazings. A secondbenefit is that peak electricitydemand is also reduced by exteriorshading devices resulting in lowerpeak demand charges from utilitiesand reduced mechanical equipmentcosts. Finally, exterior shadingdevices have the ability to reduceglare in an interior space withoutthe need to lower shades or closeblinds. This means that daylightand view are not diminished bydark tinted glazings or blocked byinterior shades. With exterior shadingdevices, glare control does notdepend on user operation.Using This PublicationThis publication shows the impactof external shading devices on theenergy use, peak demand, and glareconditions in commercial officebuildings.This publication is intended tohelp the designer quickly narrowthe range of possibilities and understandthe approximate impactsin commercial office buildings inorder to provide general guidanceduring early stages of design. Ifthere is more time and budget, thiscan be followed by a more detailedcomputer simulation of the specificbuilding and the design conditions.In the following sections, resultsare presented for six cities withdiffering climates: Minneapolis,Chicago, Washington DC, Houston,Phoenix and Los Angeles. Withineach climate, results are shown foreast-, south-, and west-facing orientations.The north orientation is notshown since the impacts of externalshading devices are small. Withineach orientation, there are resultsfor both moderate (WWR=0.30) anda large (WWR=0.60) window areas(WWR is the window-to-wall ratio).For each set of conditions, there aresix window types and five shadingconditions. As shown in Figure 1,the five shading conditions include:no shading (none), vertical fins(fins), shallow overhang (ov1), deepoverhang (ov2), and deep overhangwith fins (ov2f).For each location, orientationand window area, there is a tablesummarizing the impacts of externalshading devices. An exampleof one of these tables is shown inTable 1 for a perimeter office zonein Houston, Texas with a southfacing orientation and large glazingarea. For a given glass type, thereare five lines of data—one for eachshading condition. The “Energy”column shows the actual energy usefor each shading condition and the“Energy % Save” shows the percentsavings compared to the unshadedcase (none). Similarly, the “Peak”column shows actual peak demandand the “Peak % Save” shows thepercent savings compared to theunshaded case (none). The “Glare”column shows the weighted glareindex for each shading conditionand the “Glare % Red.” shows thepercent glare reduction comparedto the unshaded case (none).In comparing different sectionsof the publication, it is clear thatthe impacts of external shadingdevices are different depending onthe building location, the windoworientation, and window size. Inaddition, as shown in Table 1, thetype of glazing and shading deviceused also impact the results.FIGURE 1Air Movement and Control Association International (www.amca.org) Page 3


FIGURE 2 FIGURE 3250.00ANNUAL ENERGY USE—HOUSTON, TXSouth Orientation—Large Window Area (WWR=0.60)12.00PEAK ELECTRICITY DEMAND—HOUSTON, TXSouth Orientation—Large Window Area (WWR=0.60)200.0010.008.00kBtu/sf-yr150.00100.00W/sf6.004.0050.002.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fGlare ImpactsThe impact of exterior shadingdevices on glare in interior spaces isalso illustrated by Table 1. The glareindex is calculated at a point fivefeet from the window for a personfacing the side wall. A lower indexis better. A glare index of 10 is considered“just perceptible”, an indexof 16 is “just acceptable” and anindex of 22 is “just uncomfortable.”Unlike energy use and peak demand,glare reduction appears to besimilar in percentage and amountfor all glazing types. The greatestglare reduction occurs with a combinationof a deep overhang withvertical fins. The percent savingsin glare index resulting from usinga deep overhang with fins is 35.1%when applied to a clear doubleglazed window compared to 40.8%when applied to a triple glazedlow-E window. The glare index isreduced from 15 to 10 when thedeep overhang with fins are appliedto a clear double glazed window.The glare index is reduced from 14to 8 when applied to a triple glazedlow-E window. A key advantageof external shading devices is thatthey can provide glare reductionwithout the need to lower shades orclose blinds. This means that daylightand view are not diminishedby dark tinted glazings or blockedby interior shades. With exteriorshading devices, glare control doesnot depend on user operation.External shading devices can playan important role in creating moresustainable buildings with less energyuse and peak demand as wellas improved glare conditions forthe building occupants. The AMCApublication and other resources arenow available to assist designers inoptimizing façade design.ReferencesCarmody, John, 2006. External ShadingDevices in Commercial Buildings:The Impact on Energy Use, PeakDemand and Glare Control. Publishedby Air Movement and Control AssociationInternational (AMCA), 30West University Drive, ArlingtonHeights, Illinois 60004. Phone: 847-394-0150.Web: www.amca.orgCarmody, J., E. Lee, S. Selkowitz, D.Arasteh, and T. Willmert, WindowSystems for High Performance Buildings,W.W. Norton & Company,2004.Commercial Windows Web Site:www.commercialwindows.umn.eduAir Movement and Control Association International (www.amca.org) Page 5


Minneapolis, MinnesotaEast Orientation—Moderate Window AreaThe table and graphs on this pageshow the impact of external shadingdevices on an east-facing facadewith moderate window area in acommercial office building in Minneapolis,Minnesota.The impact is different dependingon the type of glazing and shadingdevice used. Six typical commercialglazings with different solar heatgain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—MINNEAPOLIS, MNEast Orientation—Moderate Window Area (WWR=0.30)Note: All cases are east-facing with a 0.30 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--2.804.204.20FinDepth (ft)-3.00--3.00160.00ANNUAL ENERGY USE—MINNEAPOLIS, MNEast Orientation—Moderate Window Area (WWR=0.30)7.00PEAK ELECTRICITY DEMAND—MINNEAPOLIS, MNEast Orientation—Moderate Window Area (WWR=0.30)140.006.00120.005.00kBtu/sf-yr100.0080.0060.00W/sf4.003.0040.0020.002.001.000.00Clear (2) B Tint (2) Low-E BTint (2)Glazing TypeLow-EClear (2)Low-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fPage 6Air Movement and Control Association International (www.amca.org)


Minneapolis, MinnesotaEast Orientation—Large Window AreaThe table and graphs on thispage show the impact of externalshading devices on an east-facingfacade with a large window areain a commercial office building inMinneapolis, Minnesota.The impact is different dependingon the type of glazing and shadingdevice used. Six typical commercialglazings with different solar heatgain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—MINNEAPOLIS, MNEast Orientation—Large Window Area (WWR=0.60)Note: All cases are east-facing with a 0.60 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--3.365.045.04FinDepth (ft)-5.00--5.00250.00ANNUAL ENERGY USE—MINNEAPOLIS, MNEast Orientation—Large Window Area (WWR=0.60)12.00PEAK ELECTRICITY DEMAND—MINNEAPOLIS, MNEast Orientation—Large Window Area (WWR=0.60)200.0010.00kBtu/sf-yr150.00100.00W/sf8.006.004.0050.002.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fAir Movement and Control Association International (www.amca.org) Page 7


Minneapolis, MinnesotaSouth Orientation—Moderate Window AreaThe table and graphs on thispage show the impact of externalshading devices on an south-facingfacade with moderate window areain a commercial office building inMinneapolis, Minnesota.The impact is different dependingon the type of glazing and shadingdevice used. Six typical commercialglazings with different solar heatgain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—MINNEAPOLIS, MNSouth Orientation—Moderate Window Area (WWR=0.30)Note: All cases are east-facing with a 0.30 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--2.804.204.20FinDepth (ft)-3.00--3.00140.00ANNUAL ENERGY USE—MINNEAPOLIS, MNSouth Orientation—Moderate Window Area (WWR=0.30)7.00PEAK ELECTRICITY DEMAND—MINNEAPOLIS, MNSouth Orientation—Moderate Window Area (WWR=0.30)120.006.00100.005.00kBtu/sf-yr80.0060.00W/sf4.003.0040.002.0020.001.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fPage 8Air Movement and Control Association International (www.amca.org)


Minneapolis, MinnesotaSouth Orientation—Large Window AreaThe table and graphs on thispage show the impact of externalshading devices on an south-facingfacade with a large window areain a commercial office building inMinneapolis, Minnesota.The impact is different dependingon the type of glazing and shadingdevice used. Six typical commercialglazings with different solar heatgain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—MINNEAPOLIS, MNSouth Orientation—Large Window Area (WWR=0.60)Note: All cases are east-facing with a 0.60 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--3.365.045.04FinDepth (ft)-5.00--5.00200.00ANNUAL ENERGY USE—MINNEAPOLIS, MNSouth Orientation—Large Window Area (WWR=0.60)12.00PEAK ELECTRICITY DEMAND—MINNEAPOLIS, MNSouth Orientation—Large Window Area (WWR=0.60)175.0010.00150.00kBtu/sf-yr125.00100.0075.00W/sf8.006.004.0050.0025.002.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fAir Movement and Control Association International (www.amca.org) Page 9


Minneapolis, MinnesotaWest Orientation—Moderate Window AreaThe table and graphs on thispage show the impact of externalshading devices on an west-facingfacade with moderate window areain a commercial office building inMinneapolis, Minnesota.The impact is different dependingon the type of glazing and shadingdevice used. Six typical commercialglazings with different solar heatgain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—MINNEAPOLIS, MNWest Orientation—Moderate Window Area (WWR=0.30)Note: All cases are east-facing with a 0.30 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--2.804.204.20FinDepth (ft)-3.00--3.00160.00ANNUAL ENERGY USE—MINNEAPOLIS, MNWest Orientation—Moderate Window Area (WWR=0.30)7.00PEAK ELECTRICITY DEMAND—MINNEAPOLIS, MNWest Orientation—Moderate Window Area (WWR=0.30)140.006.00120.005.00kBtu/sf-yr100.0080.0060.00W/sf4.003.0040.0020.002.001.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fPage 10Air Movement and Control Association International (www.amca.org)


Minneapolis, MinnesotaWest Orientation—Large Window AreaThe table and graphs on thispage show the impact of externalshading devices on an west-facingfacade with a large window areain a commercial office building inMinneapolis, Minnesota.The impact is different dependingon the type of glazing and shadingdevice used. Six typical commercialglazings with different solar heatgain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—MINNEAPOLIS, MNWest Orientation—Large Window Area (WWR=0.60)Note: All cases are east-facing with a 0.60 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--3.365.045.04FinDepth (ft)-5.00--5.00250.00ANNUAL ENERGY USE—MINNEAPOLIS, MNWest Orientation—Large Window Area (WWR=0.60)12.00PEAK ELECTRICITY DEMAND—MINNEAPOLIS, MNWest Orientation—Large Window Area (WWR=0.60)200.0010.008.00kBtu/sf-yr150.00100.00W/sf6.004.0050.002.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fAir Movement and Control Association International (www.amca.org) Page 11


Chicago, IllinoisEast Orientation—Moderate Window AreaThe table and graphs on thispage show the impact of externalshading devices on an east-facingfacade with moderate window areain a commercial office building inChicago, Illinois.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—CHICAGO, ILEast Orientation—Moderate Window Area (WWR=0.30)Note: All cases are east-facing with a 0.30 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--2.804.204.20FinDepth (ft)-3.00--3.00140.00ANNUAL ENERGY USE—CHICAGO, ILEast Orientation—Moderate Window Area (WWR=0.30)7.00PEAK ELECTRICITY DEMAND—CHICAGO, ILEast Orientation—Moderate Window Area (WWR=0.30)120.006.00100.005.00kBtu/sf-year80.0060.00W/sf4.003.0040.002.0020.001.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fPage 12Air Movement and Control Association International (www.amca.org)


Chicago, IllinoisEast Orientation—Large Window AreaThe table and graphs on this pageshow the impact of external shadingdevices on an east-facing facadewith large window area in a commercialoffice building in Chicago,Illinois.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—CHICAGO, ILEast Orientation—Large Window Area (WWR=0.60)Note: All cases are east-facing with a 0.60 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--3.365.045.04FinDepth (ft)-5.00--5.00200.00ANNUAL ENERGY USE—CHICAGO, ILEast Orientation—Large Window Area (WWR=0.60)12.00PEAK ELECTRICITY DEMAND—CHICAGO, ILEast Orientation—Large Window Area (WWR=0.60)175.0010.00150.00kBtu/sf-year125.00100.0075.00W/sf8.006.004.0050.0025.002.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fAir Movement and Control Association International (www.amca.org) Page 13


Chicago, IllinoisSouth Orientation—Moderate Window AreaThe table and graphs on thispage show the impact of externalshading devices on an south-facingfacade with moderate window areain a commercial office building inChicago, Illinois.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—CHICAGO, ILSouth Orientation—Moderate Window Area (WWR=0.30)Note: All cases are east-facing with a 0.30 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--2.804.204.20FinDepth (ft)-3.00--3.00140.00ANNUAL ENERGY USE—CHICAGO, ILSouth Orientation—Moderate Window Area (WWR=0.30)6.00PEAK ELECTRICITY DEMAND—CHICAGO, ILSouth Orientation—Moderate Window Area (WWR=0.30)120.005.00100.004.00kBtu/sf-year80.0060.00W/sf3.0040.002.0020.001.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fPage 14Air Movement and Control Association International (www.amca.org)


Chicago, IllinoisSouth Orientation—Large Window AreaThe table and graphs on thispage show the impact of externalshading devices on an south-facingfacade with a large window areain a commercial office building inChicago, Illinois.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—CHICAGO, ILSouth Orientation—Large Window Area (WWR=0.60)Note: All cases are east-facing with a 0.60 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--3.365.045.04FinDepth (ft)-5.00--5.00200.00180.00160.00ANNUAL ENERGY USE—CHICAGO, ILSouth Orientation—Large Window Area (WWR=0.60)12.0010.00PEAK ELECTRICITY DEMAND—CHICAGO, ILSouth Orientation—Large Window Area (WWR=0.60)kBtu/sf-year140.00120.00100.0080.0060.00W/sf8.006.004.0040.0020.002.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Low-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Low-E GTint (2)Low-EClear (3)Glazing TypeGlazing Typenone fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fAir Movement and Control Association International (www.amca.org) Page 15


Chicago, IllinoisWest Orientation—Moderate Window AreaThe table and graphs on thispage show the impact of externalshading devices on an west-facingfacade with moderate window areain a commercial office building inChicago, Illinois.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—CHICAGO, ILWest Orientation—Moderate Window Area (WWR=0.30)Note: All cases are east-facing with a 0.30 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--2.804.204.20FinDepth (ft)-3.00--3.00140.00ANNUAL ENERGY USE—CHICAGO, ILWest Orientation—Moderate Window Area (WWR=0.30)7.00PEAK ELECTRICITY DEMAND—CHICAGO, ILWest Orientation—Moderate Window Area (WWR=0.30)120.006.00100.005.00kBtu/sf-year80.0060.00W/sf4.003.0040.002.0020.001.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fPage 16Air Movement and Control Association International (www.amca.org)


Chicago, IllinoisWest Orientation—Large Window AreaThe table and graphs on thispage show the impact of externalshading devices on an west-facingfacade with a large window areain a commercial office building inChicago, Illinois.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—CHICAGO, ILWest Orientation—Large Window Area (WWR=0.60)Note: All cases are east-facing with a 0.60 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--3.365.045.04FinDepth (ft)-5.00--5.00200.00ANNUAL ENERGY USE—CHICAGO, ILWest Orientation—Large Window Area (WWR=0.60)12.00PEAK ELECTRICITY DEMAND—CHICAGO, ILWest Orientation—Large Window Area (WWR=0.60)175.0010.00150.00125.008.00kBtu/sf-yr100.00W/sf6.0075.004.0050.0025.002.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Low-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Low-E GTint (2)Low-EClear (3)Glazing TypeGlazing Typenone fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fAir Movement and Control Association International (www.amca.org) Page 17


Washington, DCEast Orientation—Moderate Window AreaThe table and graphs on thispage show the impact of externalshading devices on an east-facingfacade with moderate window areain a commercial office building inWashington, DC.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—WASHINGTON, DCEast Orientation—Moderate Window Area (WWR=0.30)Note: All cases are east-facing with a 0.30 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--2.804.204.20FinDepth (ft)-3.00--3.00140.00ANNUAL ENERGY USE—WASHINGTON, DCEast Orientation—Moderate Window Area (WWR=0.30)7.00PEAK ELECTRICITY DEMAND—WASHINGTON, DCEast Orientation—Moderate Window Area (WWR=0.30)120.006.00100.005.00kBtu/sf-yr80.0060.00W/sf4.003.0040.002.0020.001.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fPage 18Air Movement and Control Association International (www.amca.org)


Washington, DCEast Orientation—Large Window AreaThe table and graphs on this pageshow the impact of external shadingdevices on an east-facing facadewith a large window area in a commercialoffice building in Washington,DC.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—WASHINGTON, DCEast Orientation—Large Window Area (WWR=0.60)Note: All cases are east-facing with a 0.60 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--3.365.045.04FinDepth (ft)-5.00--5.00200.00ANNUAL ENERGY USE—WASHINGTON, DCEast Orientation—Large Window Area (WWR=0.60)12.00PEAK ELECTRICITY DEMAND—WASHINGTON, DCEast Orientation—Large Window Area (WWR=0.60)175.0010.00150.00kBtu/sf-yr125.00100.0075.00W/sf8.006.004.0050.0025.002.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fAir Movement and Control Association International (www.amca.org) Page 19


Washington, DCSouth Orientation—Moderate Window AreaThe table and graphs on thispage show the impact of externalshading devices on an south-facingfacade with moderate window areain a commercial office building inWashington, DC.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—WASHINGTON, DCSouth Orientation—Moderate Window Area (WWR=0.30)Note: All cases are east-facing with a 0.30 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--2.804.204.20FinDepth (ft)-3.00--3.00140.00ANNUAL ENERGY USE—WASHINGTON, DCSouth Orientation—Moderate Window Area (WWR=0.30)6.00PEAK ELECTRICITY DEMAND—WASHINGTON, DCSouth Orientation—Moderate Window Area (WWR=0.30)120.005.00100.004.00kBtu/sf-yr80.0060.00W/sf3.0040.002.0020.001.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fPage 20Air Movement and Control Association International (www.amca.org)


Washington, DCSouth Orientation—Large Window AreaThe table and graphs on thispage show the impact of externalshading devices on an south-facingfacade with a large window areain a commercial office building inWashington, DC.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—WASHINGTON, DCSouth Orientation—Large Window Area (WWR=0.60)Note: All cases are east-facing with a 0.60 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--3.365.045.04FinDepth (ft)-5.00--5.00200.00ANNUAL ENERGY USE—WASHINGTON, DCSouth Orientation—Large Window Area (WWR=0.60)12.00PEAK ELECTRICITY DEMAND—WASHINGTON, DCSouth Orientation—Large Window Area (WWR=0.60)175.0010.00150.00kBtu/sf-yr125.00100.0075.00W/sf8.006.004.0050.0025.002.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fAir Movement and Control Association International (www.amca.org) Page 21


Washington, DCWest Orientation—Moderate Window AreaThe table and graphs on thispage show the impact of externalshading devices on an west-facingfacade with moderate window areain a commercial office building inWashington, DC.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—WASHINGTON, DCWest Orientation—Moderate Window Area (WWR=0.30)Note: All cases are east-facing with a 0.30 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Description OverhangDepth (ft)no shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical fins--2.804.204.20FinDepth (ft)-3.00--3.00140.00ANNUAL ENERGY USE—WASHINGTON, DCWest Orientation—Moderate Window Area (WWR=0.30)7.00PEAK ELECTRICITY DEMAND—WASHINGTON, DCWest Orientation—Moderate Window Area (WWR=0.30)120.006.00100.005.00kBtu/sf-yr80.0060.00W/sf4.003.0040.002.0020.001.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fPage 22Air Movement and Control Association International (www.amca.org)


Washington, DCWest Orientation—Large Window AreaThe table and graphs on thispage show the impact of externalshading devices on an west-facingfacade with a large window areain a commercial office building inWashington, DC.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—WASHINGTON, DCWest Orientation—Large Window Area (WWR=0.60)Note: All cases are east-facing with a 0.60 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--3.365.045.04FinDepth (ft)-5.00--5.00200.00ANNUAL ENERGY USE—WASHINGTON, DCWest Orientation—Large Window Area (WWR=0.60)12.00PEAK ELECTRICITY DEMAND—WASHINGTON, DCWest Orientation—Large Window Area (WWR=0.60)175.0010.00150.00125.008.00kBtu/sf-yr100.00W/sf6.0075.004.0050.0025.002.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fAir Movement and Control Association International (www.amca.org) Page 23


Houston, TexasEast Orientation—Moderate Window AreaThe table and graphs on thispage show the impact of externalshading devices on an east-facingfacade with moderate window areain a commercial office building inHouston, Texas.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—HOUSTON, TXEast Orientation—Moderate Window Area (WWR=0.30)Note: All cases are east-facing with a 0.30 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--2.804.204.20FinDepth (ft)-3.00--3.00160.00ANNUAL ENERGY USE—HOUSTON, TXEast Orientation—Moderate Window Area (WWR=0.30)7.00PEAK ELECTRICITY DEMAND—HOUSTON, TXEast Orientation—Moderate Window Area (WWR=0.30)140.006.00120.005.00kBtu/sf-yr100.0080.0060.00W/sf4.003.0040.0020.002.001.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fPage 24Air Movement and Control Association International (www.amca.org)


Houston, TexasEast Orientation—Large Window AreaThe table and graphs on this pageshow the impact of external shadingdevices on an east-facing facadewith a large window area in a commercialoffice building in Houston,Texas.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—HOUSTON,TXEast Orientation—Large Window Area (WWR=0.60)Note: All cases are east-facing with a 0.60 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--3.365.045.04FinDepth (ft)-5.00--5.00250.00ANNUAL ENERGY USE—HOUSTON, TXEast Orientation—Large Window Area (WWR=0.60)12.00PEAK ELECTRICITY DEMAND—HOUSTON, TXEast Orientation—Large Window Area (WWR=0.60)200.0010.00kWh/sf-yr150.00100.00W/sf8.006.004.0050.002.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fAir Movement and Control Association International (www.amca.org) Page 25


Houston, TexasSouth Orientation—Moderate Window AreaThe table and graphs on thispage show the impact of externalshading devices on an south-facingfacade with moderate window areain a commercial office building inHouston, Texas.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—HOUSTON, TXSouth Orientation—Moderate Window Area (WWR=0.30)Note: All cases are east-facing with a 0.30 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--2.804.204.20FinDepth (ft)-3.00--3.00160.00ANNUAL ENERGY USE—HOUSTON, TXSouth Orientation—Moderate Window Area (WWR=0.30)7.00PEAK ELECTRICITY DEMAND—HOUSTON, TXSouth Orientation—Moderate Window Area (WWR=0.30)140.006.00120.005.00kBtu/sf-yr100.0080.0060.00W/sf4.003.0040.0020.002.001.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fPage 26Air Movement and Control Association International (www.amca.org)


Houston, TexasSouth Orientation—Large Window AreaThe table and graphs on thispage show the impact of externalshading devices on an south-facingfacade with a large window areain a commercial office building inHouston, Texas.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—HOUSTON, TXSouth Orientation—Large Window Area (WWR=0.60)Note: All cases are east-facing with a 0.60 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--3.365.045.04FinDepth (ft)-5.00--5.00250.00ANNUAL ENERGY USE—HOUSTON, TXSouth Orientation—Large Window Area (WWR=0.60)12.00PEAK ELECTRICITY DEMAND—HOUSTON, TXSouth Orientation—Large Window Area (WWR=0.60)200.0010.00kBtu/sf-yr150.00100.00W/sf8.006.004.0050.002.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fAir Movement and Control Association International (www.amca.org) Page 27


Houston, TexasWest Orientation—Moderate Window AreaThe table and graphs on thispage show the impact of externalshading devices on an west-facingfacade with moderate window areain a commercial office building inHouston, Texas.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—HOUSTON, TXWest Orientation—Moderate Window Area (WWR=0.30)Note: All cases are east-facing with a 0.30 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--2.804.204.20FinDepth (ft)-3.00--3.00160.00ANNUAL ENERGY USE—HOUSTON, TXWest Orientation—Moderate Window Area (WWR=0.30)7.00PEAK ELECTRICITY DEMAND—HOUSTON, TXWest Orientation—Moderate Window Area (WWR=0.30)140.00120.006.005.00kBtu/sf-yr100.0080.0060.00W/sf4.003.0040.0020.002.001.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fPage 28Air Movement and Control Association International (www.amca.org)


Houston, TexasWest Orientation—Large Window AreaThe table and graphs on thispage show the impact of externalshading devices on an west-facingfacade with a large window areain a commercial office building inHouston, Texas.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—HOUSTON, TXWest Orientation—Large Window Area (WWR=0.60)Note: All cases are east-facing with a 0.60 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--3.365.045.04FinDepth (ft)-5.00--5.00250.00ANNUAL ENERGY USE—HOUSTON, TXWest Orientation—Large Window Area (WWR=0.60)12.00PEAK ELECTRICITY DEMAND—HOUSTON, TXWest Orientation—Large Window Area (WWR=0.60)200.0010.00kBtu/sf-yr150.00100.00W/sf8.006.004.0050.002.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fAir Movement and Control Association International (www.amca.org) Page 29


Phoenix, ArizonaEast Orientation—Moderate Window AreaThe table and graphs on this pageshow the impact of external shadingdevices on an east-facing facadewith moderate window area in acommercial office building in Phoenix,Arizona.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—PHOENIX, AZEast Orientation—Moderate Window Area (WWR=0.30)Note: All cases are east-facing with a 0.30 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--2.804.204.20FinDepth (ft)-3.00--3.00180.00ANNUAL ENERGY USE—PHOENIX, AZEast Orientation—Moderate Window Area (WWR=0.30)8.00PEAK ELECTRICITY DEMAND—PHOENIX, AZEast Orientation—Moderate Window Area (WWR=0.30)160.00140.007.006.00kBtu/sf-yr120.00100.0080.0060.00W/sf5.004.003.0040.0020.002.001.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fPage 30Air Movement and Control Association International (www.amca.org)


W/sfPhoenix, ArizonaEast Orientation—Large Window AreaThe table and graphs on this pageshow the impact of external shadingdevices on an east-facing facadewith a large window area in a commercialoffice building in Phoenix,Arizona.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—PHOENIX, AZEast Orientation—Large Window Area (WWR=0.60)Note: All cases are east-facing with a 0.60 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--3.365.045.04FinDepth (ft)-5.00--5.00250.00ANNUAL ENERGY USE—PHOENIX, AZEast Orientation—Large Window Area (WWR=0.60)14.00PEAK ELECTRICITY DEMAND—PHOENIX, AZEast Orientation—Large Window Area (WWR=0.60)200.0012.0010.00kBtu/sf-yr150.00100.008.006.004.0050.002.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fAir Movement and Control Association International (www.amca.org) Page 31


Phoenix, ArizonaSouth Orientation—Moderate Window AreaThe table and graphs on thispage show the impact of externalshading devices on an south-facingfacade with moderate window areain a commercial office building inPhoenix, Arizona.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—PHOENIX, AZSouth Orientation—Moderate Window Area (WWR=0.30)Note: All cases are east-facing with a 0.30 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--2.804.204.20FinDepth (ft)-3.00--3.00180.00ANNUAL ENERGY USE—PHOENIX, AZSouth Orientation—Moderate Window Area (WWR=0.30)8.00PEAK ELECTRICITY DEMAND—PHOENIX, AZSouth Orientation—Moderate Window Area (WWR=0.30)160.00140.007.006.00kBtu/sf-yr120.00100.0080.0060.00W/sf5.004.003.0040.0020.002.001.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fPage 32Air Movement and Control Association International (www.amca.org)


Phoenix, ArizonaSouth Orientation—Large Window AreaThe table and graphs on thispage show the impact of externalshading devices on an south-facingfacade with a large window areain a commercial office building inPhoenix, Arizona.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—PHOENIX, AZSouth Orientation—Large Window Area (WWR=0.60)Note: All cases are east-facing with a 0.60 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--3.365.045.04FinDepth (ft)-5.00--5.00250.00ANNUAL ENERGY USE—PHOENIX, AZSouth Orientation—Large Window Area (WWR=0.60)14.00PEAK ELECTRICITY DEMAND—PHOENIX, AZSouth Orientation—Large Window Area (WWR=0.60)200.0012.0010.00kBtu/sf-yr150.00100.00W/sf8.006.0050.004.002.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fAir Movement and Control Association International (www.amca.org) Page 33


Phoenix, ArizonaWest Orientation—Moderate Window AreaThe table and graphs on thispage show the impact of externalshading devices on an west-facingfacade with moderate window areain a commercial office building inPhoenix, Arizona.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—PHOENIX, AZWest Orientation—Moderate Window Area (WWR=0.30)Note: All cases are east-facing with a 0.30 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--2.804.204.20FinDepth (ft)-3.00--3.00180.00ANNUAL ENERGY USE—PHOENIX, AZWest Orientation—Moderate Window Area (WWR=0.30)8.00PEAK ELECTRICITY DEMAND—PHOENIX, AZWest Orientation—Moderate Window Area (WWR=0.30)160.00140.007.006.00kBtu/sf-yr120.00100.0080.0060.00W/sf5.004.003.0040.0020.002.001.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fPage 34Air Movement and Control Association International (www.amca.org)


Phoenix, ArizonaWest Orientation—Large Window AreaThe table and graphs on thispage show the impact of externalshading devices on an west-facingfacade with a large window areain a commercial office building inPhoenix, Arizona.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—PHOENIX, AZWest Orientation—Large Window Area (WWR=0.60)Note: All cases are east-facing with a 0.60 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--3.365.045.04FinDepth (ft)-5.00--5.00250.00ANNUAL ENERGY USE—PHOENIX, AZWest Orientation—Large Window Area (WWR=0.60)PEAK ELECTRICITY DEMAND—PHOENIX, AZWest Orientation—Large Window Area (WWR=0.60)200.0012.0010.00kBtu/sf-yr150.00100.00W/sf8.006.0050.004.002.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fAir Movement and Control Association International (www.amca.org) Page 35


Los Angeles, CaliforniaEast Orientation—Moderate Window AreaThe table and graphs on this pageshow the impact of external shadingdevices on an east-facing facadewith moderate window area in acommercial office building in LosAngeles, California.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—LOS ANGELES, CAEast Orientation—Moderate Window Area (WWR=0.30)Note: All cases are east-facing with a 0.30 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--2.804.204.20FinDepth (ft)-3.00--3.00140.00ANNUAL ENERGY USE—LOS ANGELES, CAEast Orientation—Moderate Window Area (WWR=0.30)7.00PEAK ELECTRICITY DEMAND—LOS ANGELES, CAEast Orientation—Moderate Window Area (WWR=0.30)120.006.00100.005.00kBtu/sf-yr80.0060.00W/sf4.003.0040.002.0020.001.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fPage 36Air Movement and Control Association International (www.amca.org)


Los Angeles, CaliforniaEast Orientation—Large Window AreaThe table and graphs on thispage show the impact of externalshading devices on an east-facingfacade with a large window area ina commercial office building in LosAngeles, California.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—LOS ANGELES, CAEast Orientation—Large Window Area (WWR=0.60)Note: All cases are east-facing with a 0.60 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--3.365.045.04FinDepth (ft)-5.00--5.00200.00ANNUAL ENERGY USE—LOS ANGELES, CAEast Orientation—Large Window Area (WWR=0.60)12.00PEAK ELECTRICITY DEMAND—LOS ANGELES, CAEast Orientation—Large Window Area (WWR=0.60)175.0010.00150.00kBtu/sf-yr125.00100.0075.00W/sf8.006.004.0050.0025.002.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypesLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypesLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fAir Movement and Control Association International (www.amca.org) Page 37


Los Angeles, CaliforniaSouth Orientation—Moderate Window AreaThe table and graphs on thispage show the impact of externalshading devices on an south-facingfacade with moderate window areain a commercial office building inLos Angeles, California.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—LOS ANGELES, CASouth Orientation—Moderate Window Area (WWR=0.30)Note: All cases are east-facing with a 0.30 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--2.804.204.20FinDepth (ft)-3.00--3.00140.00ANNUAL ENERGY USE—LOS ANGELES, CASouth Orientation—Moderate Window Area (WWR=0.30)7.00PEAK ELECTRICITY DEMAND—LOS ANGELES, CASouth Orientation—Moderate Window Area (WWR=0.30)120.006.00100.005.00kBtu/sf-yr80.0060.00W/sf4.003.0040.002.0020.001.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fPage 38Air Movement and Control Association International (www.amca.org)


Los Angeles, CaliforniaSouth Orientation—Large Window AreaThe table and graphs on thispage show the impact of externalshading devices on an south-facingfacade with a large window area ina commercial office building in LosAngeles, California.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—LOS ANGELES, CASouth Orientation—Large Window Area (WWR=0.60)Note: All cases are east-facing with a 0.60 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--3.365.045.04FinDepth (ft)-5.00--5.00250.00ANNUAL ENERGY USE—LOS ANGELES, CASouth Orientation—Large Window Area (WWR=0.60)14.00PEAK ELECTRICITY DEMAND—LOS ANGELES, CASouth Orientation—Large Window Area (WWR=0.60)200.0012.0010.00kBtu/sf-yr150.00100.00W/sf8.006.0050.004.002.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fAir Movement and Control Association International (www.amca.org) Page 39


Los Angeles, CaliforniaWest Orientation—Moderate Window AreaThe table and graphs on thispage show the impact of externalshading devices on an west-facingfacade with moderate window areain a commercial office building inLos Angeles, California.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—LOS ANGELES, CAWest Orientation—Moderate Window Area (WWR=0.30)Note: All cases are east-facing with a 0.30 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--2.804.204.20FinDepth (ft)-3.00--3.00140.00ANNUAL ENERGY USE—LOS ANGELES, CAWest Orientation—Moderate Window Area (WWR=0.30)7.00PEAK ELECTRICITY DEMAND—LOS ANGELES, CAWest Orientation—Moderate Window Area (WWR=0.30)120.006.00100.005.00kBtu/sf-yr80.0060.00W/sf4.003.0040.002.0020.001.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fPage 40Air Movement and Control Association International (www.amca.org)


Los Angeles, CaliforniaWest Orientation—Large Window AreaThe table and graphs on thispage show the impact of externalshading devices on an west-facingfacade with a large window area ina commercial office building in LosAngeles, California.The impact is different dependingon the type of glazing and shadingdevice used. Seven typical commercialglazings with different solarheat gain coefficients are analyzed.The five shading conditionsanalyzed include no shading(none), vertical fins (fins), shallowoverhang (ov1), deep overhang(ov2), and deep overhang with fins,(ov2f).For each combination of glazingand shading condition, the tableshows the annual energy use, peakdemand and glare index as well asthe percent savings compared to theunshaded condition.IMPACT OF EXTERIOR SHADING—LOS ANGELES, CAWest Orientation—Large Window Area (WWR=0.60)Note: All cases are east-facing with a 0.60 window-to-wallratio and include daylighting controls.Annual energy use is expressed in kBtu per squarefoot of floor area within a 15-foot-deep perimeterzone. Peak demand is expressed in Watts persquare foot of floor area within a 15-foot-deepperimeter zone. Glare index is calculated at a point5 feet from the window for a person facing the sidewall. A lower index is better. All results were computedusing DOE-2.1E for a typical office building.See Appendix for assumptions and dimensions ofexternal shading devices. SHGC=solar heat gaincoefficient, U-value=heat transmission in Btu/hr-sf-°F, Tvis=visible transmittanceLabelnonefinsov1ov2ov2fShading Device Descriptionno shadingvertical finsshallow overhangdeep overhangdeep overhang & vertical finsOverhangDepth (ft)--3.365.045.04FinDepth (ft)-5.00--5.00200.00ANNUAL ENERGY USE—LOS ANGELES, CAWest Orientation—Large Window Area (WWR=0.60)12.00PEAK ELECTRICITY DEMAND—LOS ANGELES, CAWest Orientation—Large Window Area (WWR=0.60)175.0010.00150.00125.008.00kBtu/sf-yr100.00W/sf6.0075.004.0050.0025.002.000.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)0.00Clear (2) B Tint (2) Low-E BTint (2)Low-EClear (2)Glazing TypeLow-E GTint (2)Low-EClear (3)none fins ov1 ov2 ov2fnone fins ov1 ov2 ov2fAir Movement and Control Association International (www.amca.org) Page 41


AppendixMethod for Generating Performance DataINTRODUCTIONWindow performance was analyzedwith computer simulations.Inputs to the simulation includeda building module which could beanalyzed with different sizes andtypes of windows. The analysis wasbased on a default set of windowand lighting conditions that includesvarious climates, windowsizes, window types, shading, anddaylighting controls. The computermodel calculated a number of performancemeasures such as glare,energy use, and peak demand.This appendix provides a detaileddescription of the assumptions inthe building simulation, the inputparameter values, and the performancemeasures. These methodsand assumptions apply to all officeperformance results throughout thepublication.Building energy simulations ofcommercial window systems wereperformed using the U.S. Departmentof Energy’s DOE-2.1E buildingenergy simulation program(Winkelmann et al. 1993). TheDOE-2.1E program is the buildingindustry standard that requires asinput a geometrical description ofthe building and a physical descriptionof the building construction,mechanical equipment, end-useload schedules, utility rates, andhourly weather data to determinethe energy consumption of thebuilding. DOE-2 has been used todevelop American Society of Heating,Refrigerating and Air-ConditioningEngineers (ASHRAE) 90.1and California Title-24 Energy-EfficiencyStandards and to designmany commercial buildings overthe past twenty years.COMMERCIAL BUILDINGPROTOTYPEA generic commercial officebuilding prototype originally developedby the Lawrence BerkeleyNational Laboratory (LBNL) forASHRAE SP-41 was used for thisstudy. The prototype was modifiedby the Pacific Northwest NationalLaboratory (PNNL) (Friedrich andMessinger 1995) in support of theASHRAE Standard 90.1-1989 nonresidentialbuilding energy standards(ASHRAE 1989). The prototypewas further modified by LBNLfor this study to reflect ASHRAEStandard 90.1-1999 (changes to theASHRAE Standard 90.1-2001 werenot substantive) and to isolate relativedifferences in energy performancebetween different windowdesign strategies. The prototype is asynthetic hypothetical building, nota physically real building, with size,shell construction, heating, ventilating,and air-conditioning (HVAC)system type, operating schedules,etc. based on the mean prevailingcondition among statistical samplesand engineering judgment. Thisanalysis relies on relative performancedifferences between windowsystems; the intention is not toFigure A-1. Floor plan and section ofthe three-story prototypeTable A-1. Weather dataPage 42Air Movement and Control Association International (www.amca.org)


Figure A-2. Interior elevation ofwindow wall for window-to-wall ratios(WWR) of 0.30 and 0.60 (top to bottom);sections through the overhangand fin are given as well (see Tables 5and 6)Table A-2. ASHRAE 90.1-1999 insulation valuesTable A-3. Window placementprovide absolute data from which areader may determine energy performancefor a specific building.The three-story prototype consistsof a ground, intermediate, and rooftopfloor (Figure A-1). Each floorhas four 1500 square foot perimeterzones, each consisting of ten 10 by15 feet private offices, and a 100by 100 feet square core zone with afloor area of 10,000 square feet. Thefloor-to-floor height is 12 feet with a9-foot-high ceiling and a 3-foot-highunconditioned plenum. The totalfloor area of the model is 48,000square feet. The building was orientedto true north with each facadefacing the four cardinal directions.Six climates were modeled (TableA-1) corresponding roughly to thefive climate zones defined by theU.S. DOE’s Energy InformationAdministration (EIA 1998).Lightweight construction wasused for the building and was thesame for each climate: 4-inch brickexterior facade, built-up roofingover a 0.75-inch plywood deck, anda carpeted, 6-inch heavyweight concreteslab on grade. Insulation valuesfor the exterior wall, roof, andfloor were obtained from ASHRAEStandard 90.1-1999 for each climateand are summarized in Table A-2.An effective U-value was appliedto account for the slab-to-groundcontacttemperature variations ofthe soil.The interior was specified withadiabatic walls between perimeteroffices and standard walls betweenthe perimeter and core zone. Thesewalls were composed of 0.625-inchgypsum and metal studs. A 0.5-inchacoustical tile ceiling was specifiedfor all occupied zones and 0.167-inch lightweight concrete floorswith a carpet were specified for thetwo upper level floors.Peak occupant density was 390square feet per person in the corezones and 275 square feet perperson in the perimeter zones. Peakequipment loads were 0.75 W/sf.Scheduling corresponded to datafrom ASHRAE 90.1-1989, ELCAP,and PG&E (Friedrich and Messinger1995).WindowsFlush-mounted, non-operablewindows were modeled in theexterior wall of each perimeterzone office. Two window sizeswere modeled with a fenestrationwindow-to-wall area ratio (WWR)(which includes the area of thewhole window with frame), of0.30 and 0.60, where the wall areawas defined as the floor-to-floorexterior wall area and the floor-tofloorheight was 12 feet. Note, theASHRAE Standard 90.1-1999 usesthis same definition for WWR; howeverin previous research, WWRwas based on the glazed windowarea (see Table A-3 for equivalentWWR values). Figure A-2 gives theposition of the window in the windowwall as seen from the exterior.Table A-4. Window propertiesAir Movement and Control Association International (www.amca.org) Page 43


Window position can influence thedistribution of heat flux to interiorroom surfaces and the distributionof daylight within the room. Thehead height of the framed windowwas set flush with the ceiling at 9feet for all window areas.Several types of commerciallyavailable windows were modeled inorder to determine relative performanceimpacts for both retrofit andnew construction. Glass layers wereall 0.25 inches thick. Spectral propertiesof the glass were obtainedfrom the Optics5 (version 2.0.2) databaseand input into WINDOW4.1(windows.lbl.gov/software/default.htm)to derive the whole windowproperties shown in Table A-4.The single-pane window (type A)was modeled with a non-thermallybroken, aluminum frame (assuminga retrofit condition) while all double-panewindows were modeledwith a thermally broken, aluminumframe. The three-pane window wasmodeled with aluminum inner andouter frames with a polyamide thermalbreak between the inner andouter frames. Multipane windowswere modeled with aluminum orinsulated spacers, as indicated inTable A-4. The frame width was 3inches wide in all cases. For multipanewindows, all gaps were filledwith air. The gap width was 0.5inches for double-pane windowsand 0.79 inches for triple-pane. Theintermediate layer for the threelayerwindow was suspended, clearpolyethylene (PET) film.Exterior ShadesOverhangs and vertical fins weremodeled in DOE-2.1E as opaque,non-reflective surfaces. These obstructionsblock diffuse light fromthe sky and direct sun but reflect nolight from the ground.Overhangs. The depth of theoverhang was set to provide aprofile angle of 65 degrees or 55degrees for a fully shaded window(Figure A-2 and Table A-5). Thesesolar profile angles roughly correspondto the cooling season ofa south-facing perimeter zone inthe cold and hot climates and wereconstrained to depths deemed acceptableby standard practice. Thewidth of the overhang was madethe same width as the office module(not the window): 10 feet. Theoverhang height was set so that itslower surface was flush with thetop of the framed window opening.Fins. A single case was modeledfor fins (Figure A-2 and Table A-6).The fin depth yields an azimuthalcutoff angle of 26.6˚ for shading thefull window width (“100 percentshade”condition) and 45 degreesfor shading half the window width(“50 percent-shade” condition). Thefin was made the full height of thewindow and placed flush with theleft and right edges of the framedwindow opening.Overhangs and Fins. When theoverhang and fins were combined,the overhang width was the widthof the window. The overhang depthwas that for the 55 degree profileangle case.LightingRecessed fluorescent lighting systemswere modeled with a lightingpower density of 1.2 W/sf throughoutthe building. Heat from thelighting system was apportioned tothe interior space (60 percent) andto the unconditioned plenum (40percent).Daylighting controls were specifiedin all cases. The perimeter zoneelectric lights were dimmed linearly(continuous dimming) so as to provide50 footcandles at 10 feet fromthe window wall, centered on thewindow, and at a work plane heightof 2.5 feet.The design work plane illuminancelevel of 50 footcandlesis recommended for performingtypical office tasks by the IlluminatingEngineering Society. Therecommended illuminance level inmodern buildings has been changing.The current recommendationis for 30 footcandles where there isintensive visual display terminal(VDT) use and 50 footcandles forfiling, intermittent VDT use, andprivate offices. The reduction inthe recommended light level whereVDT use is intensive is a responseto the reflection problems withcathode-ray terminal (CRT) basedVDTs. It is generally assumed thathigher light levels would be preferredif there were not problemswith the VDTs. The recent increasein availability and popularity of flatscreen liquid crystal display (LCD)VDTs is likely to change lightingpractice and recommendations asthese screens are much less proneto veiling reflection problems. Therecommendations may return to 50footcandles, even for intensive VDTuse.The electronic dimmable ballastswere modeled with a minimumpower consumption of 33 percentand 10 percent minimum lightoutput. Surface reflectances were 70percent for ceilings, 50 percent forwalls, and 20 percent for floors.Mechanical SystemFive variable-air-volume systemswith economizers were employed:one each for perimeter zones facinga particular orientation (i.e.,north-facing perimeter zones on allthree floors were controlled by onesystem) and one for the three corezones. Such zoning facilitated ananalysis of window orientation onheating and cooling energy use. Theheating thermostat setpoint was70˚F during occupied hours with anight setback temperature of 55˚F;the cooling thermostat setpoint was75˚F with a night setback temperatureof 99˚F. Heating was providedby a gas boiler and cooling wasprovided by a hermetic centrifugalchiller and cooling tower.Table A-5 Overhang depths (ft)Table A-6. Fin depths (ft)Page 44Air Movement and Control Association International (www.amca.org)


OFFICE PERFORMANCEPARAMETERSAnnual Energy Use and PeakDemandAll annual energy performancedata are given as energy use perperimeter zone floor area (e.g.,kWh/sf-yr or kBtu/sf-yr), unlessotherwise noted.Perimeter zone lighting electricenergy use data are given withoutmodification.Perimeter zone cooling electricuse data were determined usingsystem-level extraction loadsconverted to plant-level electric usewith a fixed coefficient of performance(COP) of 3.0. Fan electricenergy use for hours when onlycooling is required was then addedto this quantity to arrive at totalperimeter zone cooling electric use.Perimeter zone “other” electricuse data are all electric end usesthat are not included in lightingand cooling, such as convenienceoutlets, and supply and return fansfor heating, heating and cooling,and float periods.Total annual electricity useincludes all electricity end uses:lighting, cooling, and other electricend uses.Perimeter zone heating energyuse data were determined usingsystem-level extraction loadsconverted to plant-level energy usewith a fixed heating efficiency factor(HEF) of 0.8. Fan electric energyuse for hours when only heatingis required was not added to thisquantity to enable total energyperformance comparisons based onfuel type.The COP and HEF efficiencyfactors represent system-to-plantefficiency, not component-levelequipment efficiencies such asthose given in ASHRAE 90.1. Sucha procedure was necessary since theDOE-2.1E program does not separatezonal energy at the plant level.These perimeter zone data enableequitable comparisons to be madeacross the entire data set.Total annual energy use (electricityand heating energy use)was computed using a source-siteefficiency of 0.33 for electricity and1.0 for natural gas. The source-siteefficiency indicates the generatingefficiency of the fuel or utility priorto its use in the simulated commercialbuilding.Peak electric demand data aregiven for the peak condition thatoccurs in each perimeter zone andare non-coincident with the wholebuilding’s peak condition. Like totalannual electricity use, peak demanddata includes all electricity enduses: lighting, cooling, and otherelectric end uses.Whole-Building HVAC SystemCapacityThe HVAC capacity of the heatingand cooling systems was determinedat the whole-building plantlevel. DOE-2 was allowed to automaticallysize the plant equipmentfor each parametric run to ensurerealistic part-load-ratio operations.For these comparisons, note thatthe perimeter zone window andlighting condition is the same for allorientations.Weighted Glare IndexFour types of data are given relatedto the visual environment: 1)annual average work plane illuminancedue to daylight, 2) percenthours that the daylight illuminanceis greater than 50 footcandles, 3)annual average glare index, and 4)percent hours that the glare index isgreater than 22. These data are givenat 5 feet from the window wall,2.5 feet above the second story floor,and centered on the window wall.The data are based on occupiedhours from 7:00 to 17:00 each dayof the year exclusive of Saturdays,Sundays, and holidays. A weightedglare index was computed based onthese data and are described below.DOE-2 computes the hourly daylightingglare indices based on theHopkinson Cornell-BRS formula.There are two issues that need to bedealt with. The first is the occupant’sview orientation. Glare willbe worse facing a window, but researchhas shown that people tendto be more tolerant of glare througha window. Glare on a side wall willbe the best case condition in that ifthe glare is unacceptable on a sidewall, it will only be worse facingthe window. It is not clear whichorientation is better for this index,as long as the results are scaled appropriately.The index was thereforebased on the glare facing the sidewall at 5 feet from the window.The second issue is the questionof how to evaluate the individualhourly values to get an overallyearly index. Numerical values ofthe glare index cover a range ofvalues where glare is rated imperceptibleby most people on up tovalues where it is rated uncomfortable.A simple average could easilyresult in a value of imperceptibleglare from individual values thatcover the range up to uncomfortableglare. It should be clear that aweighted glare index should be sensitiveto fairly infrequent periods ofperceptible or uncomfortable glare.The manner in which the glaresensation responds to multiplespatial sources provides a guide asto how to make the weighted glareindex sensitive to extreme values.The Hopkinson Cornell-BRS glareindex is actually the logarithmof a glare value. When there aremultiple glare sources, the glaresensation is the logarithm of thesum of the glare values. A straightadoption of this transformation forthe temporal average results in aweighted glare index that is actuallytoo sensitive, in that even asingle excursion returns almost themaximum value, allowing almostno discrimination between this caseand one with more excursions. Thisprocedure also gives a single largeexcursion a worse overall weightedglare index value than a case withmultiple just slightly smaller excursions.However, the procedure canbe modified by the inclusion of aconstant in the transformation toreduce the sensitivity of the averageto what seems to be a reasonablecompromise. The following formulagives an average that is sensitive toexcursions from a base value if theyoccur at a frequency of 1 percent ormore:Gavg = 4*log10(average G' over year)where the G' areG' = 10 (GI/4)and GI are the hourly glare index valuesfrom the DOE-2 runs.Air Movement and Control Association International (www.amca.org) Page 45

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