Over the past 10 years, I’ve written a lot about the many free mobile apps and calculators available to help roofing contractors sell the benefits of energy-efficient, long-lasting roofs. As a result, more than half of the reader inquiries I receive involve requests for information to obtain and use these free apps. Well, the good news is that all of the calculator apps I’ve talked about continue to be free and easily available via the Internet. So, I’m using this month’s column to provide a brief description and website link for each app to help those interested in learning more about these free tools for roofing contractors.

Cool Roof and Cool Peak Calculators

The Oak Ridge National Laboratories maintain a free online calculator that compares the energy savings of different roofing systems based on the reflectivity of the roof surface. For customers who pay a flat rate for electricity used for air conditioning, you can use the Cool Roof Calculator; and customers that pay additional demand charges for peak electricity usage can also use the Cool Peak Calculator.

Green Roof Energy Calculator

This free online calculator was developed through a collaboration between Portland State University, the University of Toronto and Green Roofs for Healthy Cities. The Green Roof Energy Calculator helps compare the annual energy performance of a building with a vegetative green roof to the same building with either a dark roof or white roof. In addition, the calculator estimates the annual stormwater runoff that can be eliminated by using a vegetative roof.


SkyCalc is a free, downloadable Excel spreadsheet that can help you determine the optimum skylighting strategy to achieve maximum lighting and HVAC energy savings for a building. SkyCalc combines information about skylight design and placement with real-world climate data that allows you to select the optimal skylight system for any building. SkyCalc is maintained by Energy Design Resources, which is funded by the California Public Utilities Commission.


PVWatts is a free online calculator developed by the National Renewable Energy Laboratory to estimate the electricity production of a grid-connected roof- or ground-mounted photovoltaic (PV) system. The system is based on simple inputs that allow homeowners, installers, manufacturers and researchers to easily gauge the performance of hypothetical PV systems that use crystalline modules. The calculator allows you to evaluate the energy production potential for a commercial rooftop PV system installed on your roofing project.

RoofPoint™ Energy and Carbon Calculator

Developed by the Center for Environmental Innovation in Roofing, the RoofPoint Energy and Carbon Calculator combines the inputs of all the calculators listed previously, plus a few more that allow you to compare the total energy profile of roofing systems. You can also use it to compute the carbon footprint of the roof. 

EUAC Calculator

The EUAC stands for Equivalent Annual Uniform Cost, which describes how you can compare the lifecycle cost of roofing systems that have different service lives. Using the EUAC calculator, you can arrive at an apples-to-apples comparison of common 10, 15, 20 and 30-year low-slope roofing systems in order to help your customers make the best decision on their long-term investment. The EUAC Calculator was introduced in 2006 and continues to be available as a free download from TEGNOS Research.

EnergyWise Calculator

EnergyWise combines several important roof design features into one calculator. First, you can compare the annual heating and cooling costs of different types of roofing systems with different insulation levels. You can also use the calculator to verify the energy code requirements for the most recent model versions. Finally, you can check to see if your roofing system needs a vapor retarder and where it should be placed within the roofing system. And as an extra benefit, you can print out an energy evaluation form ready for inserting in your roofing proposal. EnergyWise is a free online calculator sponsored by the National Roofing Contractors Association that requires registration.

Athena Impact Estimator

Architects and building designers across North America use the Impact Estimator to evaluate the environmental impacts of whole buildings and key building components. As a roofing contractor, you can use it to compare the green footprint of different roofing systems, including key environmental factors like global warming potential, ozone depletion potential and many more. The Impact Estimator was developed by the Athena Sustainable Materials Institute, and it’s available for free download on the Athena website. Registration is required.

If you’re interested in learning more about how to use these tools, please consider signing up for the next Commercial Roofing Boot Camp. It’s a 10-week online roofing design course that combines video lessons, reading assignments and hands-on calculations using all the apps listed above.