DOE Cool Roof Calculator
Estimates Energy and Peak Demand Savings for Flat Roofs with Non-Black Surfaces
- Developed by the U.S. Department of Energy's Oak Ridge National Laboratory (Version 2.0)
- This version of the calculator is for large facilities that purchase electricity with a demand charge based on peak monthly load. If you have a small or medium-sized facility that purchases electricity without a demand charge, run the CoolCalcEnergy version to estimate the savings in energy charges from using solar radiation control.
- What you get out of this calculator is only as good as what you put in. If you CLICK HERE , you'll find help in figuring out the best input values. Some things, such as the weathering of the solar radiation control properties and the effects of a plenum, are especially important. You'll also find help in figuring out your heating
and cooling system efficiencies and proper fuel prices.
- To compare two non-black roofs, print out results of separate estimates for each vs. a black roof. Manually compute the difference in savings to compare the two non-black roofs.
- If your energy costs are determined with both on-peak and off-peak rates, print out results of separate estimates with on-peak then off-peak rates. Use appropriate demand charges for the same roof in both estimates. Judge what fraction of the savings with on-peak rates is appropriate.
| My City | |
| Click to see Data for All 243 Locations | |
| My Proposed Roof: | |
| R-value (HIGH=20; AVG=10; LOW=5) [h·ft²·°F/Btu] | |
| Solar reflectance, SR (HIGH=80; AVG=50; LOW=10) [%] | |
| Infrared emittance, IE (HIGH=90; AVG=60; LOW=10) [%] |
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| My Energy Costs and Equipment Efficiencies: | |
| Summertime cost of electricity (HIGH=0.20; AVG=0.10; LOW=0.05) [$/KWh] | |
| Air conditioner efficiency (COP) over cooling season (HIGH=2.5; AVG=2.0; LOW=1.5) | |
| Energy source for heating (choose one) | Electricity Fuel |
| If electricity, wintertime cost (HIGH=0.20; AVG=0.10; LOW=0.05) [$/KWh] | |
| If fuel, cost (Natural gas: HIGH=1.00; AVG=0.70; LOW=0.50) [$/Therm] | |
| (Fuel oil: 2002 East coast=0.85; 2002 Midwest=0.70) [$/Therm] | |
| Heating system efficiency (Furnace or boiler: HIGH=0.8; AVG=0.7; LOW=0.5) | |
| (Electric heat pump: HIGH=2.0; AVG=1.5) (Electric resistance: 1.0) | |
| My Electricity Demand Charges and Duration: | |
| Demand charge during cooling season (HIGH=15.00; AVG=10.00; LOW=5.00) [$/KW] | |
| Months charged for peak demand (Typical = 6) [-] | |
| Total Annual Energy + Demand Savings (relative to a black roof) [$/ft² per year] | |
| Cooling energy savings [$/ft² per year] | |
| Heating energy savings (heating penalty if negative) [$/ft² per year] | |
| Cooling season demand savings [$/ft² per year] | |
| Insulation in
Black Roof for Same Total Annual Energy Savings (ignores demand savings): |
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| Upgrade from
R- to
R-[h·ft²·°F/Btu]
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| Details of Energy and Demand Savings: | |
| Heating degree days for location chosen [Annual °F-day] | |
| Cooling degree days for location chosen [Annual °F-day] | |
| Solar load for location chosen [Annual average Btu/ft² per day] | |
| Cooling load for black roof (SR=5%;IE=90%) [Btu/ft² per year] | |
| Heating load for black roof (SR=5%;IE=90%) [Btu/ft² per year] | |
| Cooling load for proposed roof [Btu/ft² per year] | |
| Heating load for proposed roof [Btu/ft² per year] | |
| Average heat load reduction during cooling season [Btu/ft² each month] | |
| Maximum heat load reduction during cooling season [Btu/ft²] |
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