Improvements to the home include installing low-E gas-filled windows, changing all light bulbs to compact fluorescents, and replacing the ceiling insulation with spray polyurethane foam insulation on the underside of the roof deck and attic walls to make it an unvented, semi-conditioned space.

“An unvented attic is particularly helpful in climates where heating and cooling equipment is located in the attic,” said Chris Porter, building science manager for BioBased Insulation. “Modifying the attic to create an indirectly conditioned space helps significantly reduce energy consumption and improves mechanical equipment performance.”

High-performance improvements to the third home made it a near zero energy home with a HERS rating of 34 and a measured space heating energy savings of 65 percent compared to the builder home.

While more extensive, some of the improvements could still be made to a deep retrofit of an existing home. They included, 2.5 kW solar panels, solar hot water heater, triple-layered windows with an R-value of 7, structurally insulated sheathing and insulation in the walls, and R49 attic insulation with radiant barrier sheathing. The builder was able to downsize to one, two-ton heat pump because of the envelope improvements.

“With three houses with actual identical simulated occupancy we will have research capabilities that are world-unique,” Christian said. “And the really exciting thing is that these homes will be available for research for seven years, so we will be able to replace, test and accelerate the development of even more efficient technologies.”