A roof assembly can play a vital role in reducing a building's energy consumption. To assist roofing professionals with installing energy-efficient roof assemblies, in 2007, NRCA, the Polyisocyanurate Insulation Manufacturers Association (PIMA) and The Roofing Industry Alliance for Progress developed EnergyWise Roof Calculator Online. The calculator is a Web-based application that allows roofing professionals to construct virtual roof assemblies to evaluate thermal efficiency and estimate energy costs via comparison with other roof assemblies absent other building envelope components. The calculator also can be used to determine minimum thermal insulation requirements established by ASHRAE Standard 90.1, "Energy Standard for Buildings Except Low-Rise Residential Buildings."
However, EnergyWise Roof Calculator Online has some limitations. You should be aware of them so you don't overestimate a roof assembly's energy savings and subsequent cost savings for building owners.
EnergyWise Roof Calculator Online is intended to compare an existing roof assembly with a proposed new roof assembly or to compare multiple proposed new roof assemblies. The calculator examines energy costs related to roof assemblies only; it does not include walls, windows, or internal building components and operations.