Energy Analysis for Window Films Applications in Florida Offices

Transcription

1 Energy & Environmental Solutions Energy Analysis for Window Films PREPARED FOR: INTERNATIONAL WINDOW FILM ASSOCIATION P.O. BOX 3871 MARTINSVILLE, VA PREPARED BY: CONSOL 5757 PACIFIC AVENUE, SUITE 220 STOCKTON, CA TEL: (209) / FAX: (209) CONTACT: MIKE HODGSON JULY 2, 2014

2 TABLE OF CONTENTS ENERGY ANALYSIS FOR WINDOW FILMS APPLICATIONS IN FLORIDA OFFICES... 1 ENERGY ANALYSIS FOR WINDOW FILMS APPLICATIONS IN FLORIDA OFFICES... 2 PURPOSE OF THIS STUDY/ SCOPE... 2 ENERGY ANALYSIS... 2 RESULTS... 3 CONCLUSIONS... 9 APPENDIX..10 TABLE OF FIGURES Figure 1: Office Retrofits: Typical Electricity Use (Tampa, Single Pane)... 4 Figure 2: Office Retrofits: Cooling Electricity Use (Tampa, Single Pane)... 4 LIST OF TABLES Table 1: Heating and Cooling Degree Days... 2 Table 2: Properties of Windows Studied for the Large Office Model... 3 Table 3: Jacksonville ROI for Existing Offices with Single Pane Glass... 5 Table 4: Jacksonville ROI for Existing Offices with Double Pane Glass... 6 Table 5: Tampa ROI for Existing Offices with Single Pane Glass... 6 Table 6: Tampa ROI for Existing Offices with Double Pane Glass... 7 Table 7: West Palm Beach ROI for Existing Offices with Single Pane Glass... 7 Table 8: West Palm Beach ROI for Existing Offices with Double Pane Glass... 8 Table 9: Miami ROI for Existing Offices with Single Pane Glass... 8 Table 10: Miami ROI for Existing Offices with Double Pane Glass... 9 Copyright IWFA November 4,

3 Energy Analysis for Window Films Purpose of This Study/ Scope The purpose of this study is to determine the cost-effectiveness of energy control window films in offices in Florida. If cost effective, window films should be included in energy and green codes as well as energy efficiency programs and incentives in Florida. Energy Analysis Description of Existing Baselines The office building modeled in the study is the EnergyPlus Commercial Building Benchmark Model developed by the U.S. Department of Energy (DOE), titled large office building. The energy features used to determine building performance were the DOE Reference Building Large Office Pre The office building is 12 stories with 498,588 square feet of conditioned floor area. The window-to-wall ratio was 38%. Office space conditioning is supplied by boilers (heating) and chillers (cooling). The occupancy schedule was 8 AM to 5 PM Monday through Friday with two hour shoulders to achieve and maintain occupancy comfort. Description of Variables The offices were simulated with energy features from the relevant (pre-1980) energy code requirements in four Florida locations with city specific weather files. The cities were chosen in order to get a range of climate conditions and representative areas with the greatest population. The cities were Jacksonville, Tampa, West Palm Beach and Miami. Jacksonville, Tampa and West Palm Beach are located in the International Energy Conservation Code (IECC) Climate Zone 2 while Miami is in IECC Climate Zone 1. Both zones are considered hot and humid climates. To get a better understanding of the specific city climates, the heating and cooling degree days for these four cities are listed below in Table 1. These cities are dominated by cooling load. Table 1: Heating and Cooling Degree Days Heating Degree Days Cooling Degree Days Jacksonville 1,434 2,511 Tampa 725 3,427 West Palm Beach 323 3,891 Miami 20 4,198 Using data from window film manufacturers and the National Fenestration Rating Council (NFRC) Certified Products Directory, the window films on the market were characterized into three groups, good, better, and best options, and a rounded median value chosen for solar heat gain coefficient Copyright IWFA November 4,

4 (SHGC) and U-factor. The values used are detailed in Table 2, shown below. For the office building model, the visible transmittance is also modeled for the purposes of evaluating daylighting design. The films were evaluated with and without an impact on U-factor to account for the variations in different manufacturers products, as some do not achieve significant U-factor differences, yet still achieve significant savings through limiting solar heat gain (see Appendix). The good, better, and best categories in the large office model represent these basic technology films which primarily limit solar heat gain. The better (u) and best (u) categories represent spectrally selective and spectrally selective with low-e technology films, respectively. Table 2: Properties of Windows Studied for the Large Office Model without good better best better(u) best(u) SHGC Single Double U-factor Single Double VT Single Double Cost/ft 2 $4.00 $4.00 $4.00 $5.50 $7.00 Simulation Software The simulation software used for the commercial model is Energy Plus v6.0 which is modeling software from the Department of Energy. This simulation model runs as an 8,760 hour annual simulation. Energy Plus takes into account building system interactions with each other and with building envelope features. The simulations were run with daylighting controls active, since window film can lower the visible light transmittance which interacts with lighting controls of energy conscious designs in large office buildings. Office simulations were run in each of the four cardinal directions and the energy usage was averaged over the four orientations. Results For commercial applications, the return on investment (ROI) is the deciding factor in implementing an energy measure. Figure 1 shows the typical electricity breakdown in the large office building by end use. Window films affect the cooling load of the building. Copyright IWFA November 4,

5 Electricity Use in MWh Electricity Use in MWh Energy Analysis for Window Films Office Retrofits Typical Electricity Use (Tampa, Single Pane) 9,000 8,000 7,000 6,000 5,000 4,000 3,000 Heat Rejection Pumps Fans Exterior Equipment Interior Equipment 2,000 1,000 0 no film single good single better single best single better U best U Exterior Lighting Interior Lighting Cooling Figure 1: Office Retrofits: Typical Electricity Use (Tampa, Single Pane) When the cooling electricity is isolated from this load data (see Figure 2) the impact of window film is clearer. Figure 2 demonstrates the effect that window films have on space cooling, which is the majority of the savings (along with reduced fan energy which is the other end use involved in cooling the building) from installing window film. Window films can reduce space cooling electricity use by up to 20%. Office Retrofits Space Cooling Electricity Use (Tampa, Single Pane) 2,000 1,800 1,600 1,400 1,200 1, no film single good single better single best single better U best U Cooling Figure 2: Office Retrofits: Cooling Electricity Use (Tampa, Single Pane) Copyright IWFA November 4,

6 Facility operators of office buildings decide on energy improvements by how quickly they pay for themselves. This is described as return on investment or ROI. The results presented in the following tables are the return on investment for the application of various types of window films. In existing offices, window film represents a significant opportunity for cost effective energy savings. Return on investment ranges from 8% to 77% annually depending on climate zone, existing single or dual pane windows, window film, and utility rate as detailed in Table 3 through Table 10. Electricity costs used for annual cost savings are the average commercial price of electricity for Florida as estimated from Florida Power and Light commercial rate with adjusted storm charges effective June The cost was cents per kilowatt hour (kwh). As Florida utilities moves toward time-of-use (TOU) or dynamic pricing rates the higher TOU rate of cents per kilowatt hour was used to determine the effective of peak energy load savings from window film. The cost of TOU or peak kwh used was the kwh cost from the dynamic price response pilot funded by the Florida Public Utility Commission in As utilities align their electricity charges with their power costs TOU rates will become more prevalent. Existing Offices in Jacksonville Table 3: Jacksonville ROI for Existing Offices with Single Pane Glass SINGLE PANE no film Good better better U Best best U Total Electricity (MWh) 7,974 7,736 7,643 7,622 7,476 7,434 Total Gas (Therms) 20,046 17,613 16,632 14,905 15,246 11,128 Energy Cost $959,203 $928,712 $916,738 $912,466 $895,602 $886,521 Annual Cost Savings - $30,491 $42,465 $46,737 $63,601 $72,682 Annual ROI - 15% 21% 17% 32% 21% Simple Payback Peak Energy Cost $2,080,978 $2,017,011 $1,991,921 $1,984,644 $1,947,216 $1,932,290 Peak Cost Savings - $63,966 $89,056 $96,334 $133,762 $148,688 Peak Annual ROI - 32% 45% 35% 67% 43% Peak Simple Payback Florida Public Service Commission, Docket No EG; Order No. PSC TRF-EG; Issued: June 13, 2011, page 3 Copyright IWFA November 4,

7 Table 4: Jacksonville ROI for Existing Offices with Double Pane Glass DOUBLE PANE no film good better better U best best U Total Electricity (MWh) 7,844 7,718 7,667 7,646 7,492 7,466 Total Gas (Therms) 14,941 13,569 13,082 12,105 11,529 9,399 Energy Cost $938,627 $922,481 $915,928 $912,405 $893,721 $888,484 Annual Cost Savings - $16,147 $22,699 $26,223 $44,907 $50,143 Annual ROI - 8% 11% 10% 22% 14% Simple Payback Peak Energy Cost $2,042,023 $2,008,251 $1,994,460 $1,987,914 $1,947,604 $1,938,701 Peak Cost Savings - $33,772 $47,563 $54,109 $94,419 $103,322 Peak Annual ROI - 17% 24% 20% 47% 30% Peak Simple Payback In the heating and cooling climate of Jacksonville, the ROI ranges from 8% to 67%. Applying window film on single pane windows provide an ROI up to a 67%, while adding film to double pane windows will provide an ROI up to 47%. Existing Offices in Tampa Table 5: Tampa ROI for Existing Offices with Single Pane Glass SINGLE PANE no film good better better U best best U Total Electricity (MWh) 8,315 8,044 7,939 7,919 7,748 7,714 Total Gas (Therms) 12,500 10,120 9,237 8,320 7,977 5,896 Energy Cost $991,671 $957,252 $944,079 $940,731 $920,243 $914,207 Annual Cost Savings - $34,419 $47,592 $50,940 $71,428 $77,464 Annual ROI - 17% 24% 19% 36% 22% Simple Payback Peak Energy Cost $2,161,414 $2,088,762 $2,060,922 $2,054,688 $2,010,136 $1,999,417 Peak Cost Savings - $72,652 $100,492 $106,726 $151,278 $161,997 Peak Annual ROI - 36% 50% 39% 76% 46% Peak Simple Payback Copyright IWFA November 4,

8 Table 6: Tampa ROI for Existing Offices with Double Pane Glass DOUBLE PANE no film good better better U best best U Total Electricity (MWh) 8,178 8,033 7,974 7,953 7,781 7,755 Total Gas (Therms) 9,233 7,999 7,551 6,956 6,240 5,129 Energy Cost $972,223 $953,803 $946,395 $943,342 $922,443 $918,165 Annual Cost Savings - $18,420 $25,828 $28,881 $49,780 $54,058 Annual ROI - 9% 13% 11% 25% 15% Simple Payback Peak Energy Cost $2,122,700 $2,083,769 $2,068,053 $2,062,076 $2,017,076 $2,009,038 Peak Cost Savings - $38,930 $54,647 $60,624 $105,624 $113,662 Peak Annual ROI - 20% 27% 22% 53% 33% Peak Simple Payback In the more cooling dominated Tampa climate, the ROI ranges from 9% to 76%. Single pane existing windows provide an ROI from 17% to 76%. Adding film to double pane windows will provide an ROI of 9% to 53% annually. Existing Offices in West Palm Beach Table 7: West Palm Beach ROI for Existing Offices with Single Pane Glass SINGLE PANE no film good better better U best best U Total Electricity (MWh) 8,457 8,176 8,070 8,051 7,877 7,852 Total Gas (Therms) 7,681 5,606 4,920 4,441 4,084 3,118 Energy Cost $1,003,388 $968,236 $955,081 $952,346 $931,543 $927,594 Annual Cost Savings - $35,152 $48,307 $51,042 $71,845 $75,794 Annual ROI - 18% 24% 19% 36% 22% Simple Payback Peak Energy Cost $2,192,990 $2,118,356 $2,090,318 $2,084,896 $2,039,671 $2,032,177 Peak Cost Savings - $74,634 $102,672 $108,094 $153,319 $160,813 Peak Annual ROI - 37% 51% 39% 77% 46% Peak Simple Payback Copyright IWFA November 4,

9 Table 8: West Palm Beach ROI for Existing Offices with Double Pane Glass DOUBLE PANE no film good better better U best best U Total Electricity (MWh) 8,327 8,176 8,117 8,098 7,919 7,895 Total Gas (Therms) 5,558 4,545 4,231 3,870 3,300 2,767 Energy Cost $985,986 $967,198 $959,889 $957,248 $935,681 $932,309 Annual Cost Savings - $18,789 $26,098 $28,739 $50,306 $53,677 Annual ROI - 9% 13% 10% 25% 15% Simple Payback Peak Energy Cost $2,157,375 $2,117,368 $2,101,707 $2,096,350 $2,049,705 $2,042,953 Peak Cost Savings - $40,008 $55,668 $61,026 $107,671 $114,422 Peak Annual ROI - 20% 28% 22% 54% 33% Peak Simple Payback In the West Palm Beach climate the ROI ranges from 9% to 77%. Single pane existing windows provide an ROI of 18% to 77%, while adding film to double pane windows will provide 9% to 54% ROI. Existing Offices in Miami Table 9: Miami ROI for Existing Offices with Single Pane Glass SINGLE PANE no film good better better U best best U Total Electricity (MWh) 8,524 8,248 8,146 8,131 7,960 7,934 Total Gas (Therms) 5,762 3,913 3,348 3,029 2,661 2,070 Energy Cost $1,009,431 $975,049 $962,423 $960,333 $939,782 $936,210 Annual Cost Savings - $34,382 $47,008 $49,099 $69,649 $73,221 Annual ROI - 17% 24% 18% 35% 21% Simple Payback Peak Energy Cost $2,208,587 $2,135,370 $2,108,343 $2,104,143 $2,059,484 $2,052,362 Peak Cost Savings - $73,217 $100,243 $104,444 $149,102 $156,224 Peak Annual ROI - 37% 50% 38% 75% 45% Peak Simple Payback Copyright IWFA November 4,

10 Table 10: Miami ROI for Existing Offices with Double Pane Glass DOUBLE PANE no film good better better U best best U Total Electricity (MWh) 8,399 8,252 8,196 8,176 7,996 7,975 Total Gas (Therms) 4,076 3,197 2,922 2,681 2,215 1,895 Energy Cost $992,898 $974,753 $967,848 $965,298 $943,651 $940,754 Annual Cost Savings - $18,145 $25,050 $27,601 $49,247 $52,144 Annual ROI - 9% 13% 10% 25% 15% Simple Payback Peak Energy Cost $2,174,348 $2,135,590 $2,120,769 $2,115,463 $2,068,518 $2,062,549 Peak Cost Savings - $38,758 $53,579 $58,885 $105,831 $111,799 Peak Annual ROI - 19% 27% 21% 53% 32% Peak Simple Payback In the hot, cooling dominated Miami climate the ROI ranges from 9% to 75% annually. Single pane existing windows provide an ROI of 17% to 75%, while adding film to double pane windows will provide a 9% to 53% ROI. Conclusions Existing office buildings are an ideal opportunity for window film retrofits. They contain a large amount of glazing and cooling loads which typically dominate the energy use. The ROIs are high, even before utility incentives, which could be substantial. Installing window films in existing office buildings offers an 8% to 77% ROI. In general, the best window film outperformed the other window films. The ROIs for this film ranged from the 22% to the 77%. The simple payback for installing best window film is approximately 1.4 to 2.9 years when installed on single pane windows and 2.0 to 4.1 years when installed on dual pane windows depending on cost of electricity. The standard improved SHGC films gave better ROI than the more expensive options of spectrally selective (better U) or spectrally selective with low-e films (best U). The energy saved by these low U- factor options is outweighed in office buildings by the higher cost for these technologies. This is due to office buildings being dominated by cooling loads in the cooling dominated Florida climate zones. The cost to improve SHGC from one standard film to the next is negligible (see Appendix), but the loss of visible transmittance can impact the choice of film between these options, balancing energy savings with such concerns as occupant comfort and exterior views. Existing office buildings are a very attractive market for window film products. High ROIs can attract building managers to invest in this energy efficiency technology. The payback periods will shorten if utility program incent window film installation. The existing office building retrofits represent a large market for energy efficiency improvements with minimum disruption to the building occupants. Copyright IWFA November 4,

11 Appendix IWFA Longevity Statement Approved September 26, 2014 Window Films were developed nearly 50 years ago using clear polyester film coated with a thin layer of metal and an adhesive on one side designed to apply the film to the inside of window glass. The metal coating helped to reflect the solar heat out of the home or office. Over time, window films have been improved with the use of UV resistant materials, different metals and/or film technologies, better construction and more robust scratch-resistant surface coatings. All of these advancements have generally helped to improve the longevity, or life expectancy, of window films for interior applications. There has always been a need for some applications where the window film is to be applied on the exterior of the glass. The original window films were not designed to stand up to harsher environmental conditions when exposed to the outside elements, i.e. direct sun, rain, wind, snow and pollutants. The use of interior window films on the exterior provided good solar performance but typically a relatively short life due to outside exposure. As interior window films have improved their longevity from original expectations of 2 to 5 years to now often approaching 20+ years of performance, so have window films designed for exterior applications likewise improved. Exterior window films have also generally evolved and improved their durability by using newer technologies and special UV-resistant materials and coatings. Interior window films applications still typically may last two (2) to three (3) times longer than exterior window films on the outside. However, the improvement of the exterior-designed window films have enabled several of these films to weather the outside exposure significantly better than previous industry offerings, and provide a more meaningful life expectancy. Even today, most window films are still applied on the interior of the building, typically due to ease of access and longer life spans; however, these advancements in weatherability and durability of exterior films have earned greater acceptance in the marketplace than ever before. Copyright IWFA November 4,