Retrofit Turns Energy-Guzzling Home into Energy Producer
The extensive renovation achieved an 80% reduction in energy usage.
Why build a new house when you can renovate an existing one, saving resources and materials while enhancing the old home’s performance with highly efficient insulation, HVAC equipment, air sealing, and windows?
That’s what Sara and Gareth Ross were thinking when they purchased an 1880s two-story house in Amherst, Mass., complete with green and white asbestos shake siding over lead-painted clapboard and a brick veneer addition. The roof was falling, the chimneys needed rebuilding, and the walls were uninsulated.
Despite its lack of curb appeal, the home’s location was attractive, within walking distance to the town center and to shops, schools, and the local farmers market. In addition, its southern orientation was ideal for passive solar heating during cold New England winters, and at 2,000 square feet (plus 900-square-foot unfinished attic) the house would provide ample space for the Ross’ family of four.
Although it was sorely in need of a facelift inside and out, the couple decided against demolishing the home and instead undertook a major renovation that would exponentially increase the home’s level of performance while opening up and modernizing the interior. They also chose to renovate the attic into a guest suite and office.
The deep energy retrofit included a comprehensive insulation and air sealing package that provided an 80% reduction in energy usage compared with a traditionally built home of the same size. Project manager Andrew Webster of Amherst-based Coldham & Hartman Architects used a foam in/foam out approach that provided a high R-value with no loss of existing square footage and a robust air barrier. He filled interior cavities with Icynene open-cell foam and clad the exterior with Dow Tuff-R foil-faced foam.
Combined with an equally efficient roof assembly, Fibertec triple-glazed windows, and a low window/wall ratio, the airtight envelope provided whole-assembly R-values of 20 for the basement walls, 34 for exterior walls, and 57 for the roof. This reduced the estimated peak winter heat loss from more than 100,000 BTU/h to less than 30,000. The maximum cooling load was reduced from an estimated 6.8 tons to less than 1.5 tons, a more than 75% reduction in heating and cooling needs.
The old boiler, 40-plus-year-old furnace, and hot water tank were replaced with state-of-the-art high-efficiency equipment, including:
–a Variable Refrigerant Flow (VRF) heating and cooling system from Mitsubishi Electric, which allowed the home’s less frequently used guest suite and office to be zoned separately;
–a Steibel Eltron heat pump hot water system; and
–a Venmar EKO 1.5 HRV for mechanical ventilation.
After researching federal and state incentives, the owners decided to implement one more technology that would push their project from energy efficient to energy producing: a 12.4 kW solar PV system from SunPower. Averaged over its first year of operation, the $70,000 grid-tied system produced one-third more energy than the home used. In the first six months of occupancy, the house earned $416 from the electric company in excess electricity.
Thanks to the extreme upgrades, the house qualified for a $32,000 Deep Energy Retrofit rebate from Western Massachusetts Electric and won the 2012 Northeast Sustainable Energy Association's Net Zero Challenge. It is also the eighth home in North America to meet the requirements of the1,000 Home Challenge, an initiative of Pennsylvania-based home performance education organization ACI.
The 1,000 Home Challenge aims to demonstrate how remodelers, designers, contractors, and homeowners can drastically upgrade existing houses in order to alter their environmental impact, says Linda Wigington, ACI's director of deep energy reduction initiatives. Homes in the Challenge must show energy usage for one year that meets a customized threshold of at least a 70% better than average. In projects such as the Ross home where previous energy use information is not available, the threshold is based on location, square footage, and occupancy.
“We’re showing that we can be doing things in a way that’s not a little bit better or better than average but significantly better,” she says.
With its state-of-the-art facelift, the Ross home now performs better than most new houses, Webster points out. “This was a chance to demonstrate the strategies that could be used in all kinds of existing housing stock, to show that older homes aren’t lost causes,” he says.
Jennifer Goodman is Senior Editor for EcoHome.http://soc.li/uhpx42