By: Chris Casey, Sales Representative - Architectural Products
The goal of LEED and the USGBC is an admirable one: “By using less energy, LEED-certified buildings save money for families, businesses and taxpayers; reduce greenhouse gas emissions; and contribute to a healthier environment for residents, workers and the larger community.”
I recently conducted an AIA accredited presentation for an architectural firm that has embraced the worthy goal of designing a school building that will apply for LEED Silver status. The specifications overall were structured to maximize the energy efficiency of the building, and the roof in particular is specified to be 3.5″, R-22 polyisocyanurate, with a fully-adhered white PVC membrane.
Here’s where things go off the rails; according to the findings made by the National Roofing Contractors Association in Professional Roofing magazine, December 2010, 3.5″ of polyiso is really only R-17.5.
So what happens when a roof has R-4.5 less than it was designed to have?
- The building is less energy efficient
- The building’s mechanical systems must work harder to compensate
- More fuel is required to power those systems, leading to increased greenhouse gas emissions
- It is more expensive for the school to heat and cool the interior
Using some rough calculations, you can determine that, based on the size and physical location of the school, the building will burn approximately 7000 more BTUs per KWh, and the additional energy cost will be in the neighborhood of $2000 per year more than it would be if the roof were truly functioning at R-22.
This result is a direct contradiction of the goals stated by the USGBC for the LEED program.
I would urge designers to use the NRCA recommendation of R-5 per inch for polysio in areas of the country with heating conditions.
I would further encourage the USGBC to adopt the R-5 recommendation, in order to help protect the integrity of the LEED certification program.
