In San Antonio, Texas, CPS Energy is taking a closer look at energy efficiency in three homes with identical floor plans but varied degrees of efficiency.
The company had the three homes built and sold them with the understanding that the owner’s energy use would be carefully monitored for research purposes. The control home was designed to the builder’s usual standards, the second one was given high-efficiency appliances, more efficient heating and cooling systems, and better insulation. The third home had the same features as the second home, plus solar roof tiles and spray foam insulation in the walls and attic.
Though the study is just over halfway complete, the U.S. Energy Department is reportedly keeping an eye on the findings, among them the fact that spray foam insulation was found to be more efficient than fiberglass because it effectively seals the home’s “thermal envelope” by filling in small cracks in the home.
In fact, the home with solar panels and spray foam insulation was found to have 70% fewer air changes per hour than the control home. The second home, which had a combination of foam and fiberglass insulation had 40% fewer. In the past, homeowners had used fiberglass batting with a minimum of a 6-inch thickness, but this was often very expensive and didn’t significantly cut air flow.
The utility company already offers a rebate program for existing homes that use spray foam insulation (federal tax incentives are also available), and now they say they have the numbers to back it up. The numbers are reportedly in line with federal guidelines.
Findings form the study will help the utility company create incentive programs for builders and residents. The company hopes to conserve 771 megawatts of power by 2020, which would eliminate the need to build an additional power plant.