The building insulated with the open cell spray foam used 28% less energy per square foot than the building insulated with fiberglass, even though the fiberglass-insulated building was 1,500 square feet smaller. During the coldest months of the year, the building insulated with the open cell spray foam was even more efficient than the smaller, fiberglass-insulated building and used 45% less energy.
During the months February, March and April, the building insulated with the open cell spray foam used fewer kilowatts per hour than the smaller, fiberglass-insulated building, peaking at 74% more efficient during the month of March.
The building insulated with open cell spray foam used significantly less energy per square foot over the course of a year than the fiberglass-insulated building. The spray foam-insulated building outperformed the fiberglass-insulated building over the course of the year because the tight building envelope created by the open cell insulation prevented air infiltration and exfiltration, the number one cause of energy loss in a structure. The inability of the fiberglass insulation to seal the building envelope causes the heating and cooling system to work harder to maintain a stable temperature, which increases utility bills.