Posted on August 18, 2015 by Hannah McKenzie.
Chatham Habitat for Humanity has been participating in the SystemVision program since its launch in 2001. They recently completed a home where they were fortunate enough to partner with the North Carolina non-profit, Grid Free! NC, who donated a 2.5kW rooftop solar array. The inverter for the system was donated by another North Carolina non-profit, United Solar Initiative. A solar log monitor was also donated by Solar Data Systems. The array could produce an average of 318 kilowatt hours of energy per month, or about $35 worth of electricity. In spring and fall months, the home could approach net zero electric consumption.
The homeowner purchasing this home is very excited about the PV system and about moving from the place they have been renting to an energy efficient Habitat home. “I’m very excited about the solar panels, and to see how they work,” she said. “Our electricity bills have been over $200/month in the summer at times, so I’m really looking forward to lower bills!”
The size of this lot afforded Chatham Habitat the ability to site this house optimally for both active and passive-solar gain. Larger windows were installed on the south side and calculations done to determine optimal window height and eve overhang so these windows will be fully shaded during the three hottest months of the year and receive full sun during the three coldest months.
Calculations were also done to achieve Joseph Lstiburek’s recommended 60%/40% eve to ridge vent openings in order to slightly pressurize the attic space, reducing the draw of conditioned air from the house.
Other energy efficiency features incorporated into this home include advanced air sealing measures and Optimum Value Engineering framing methods like 24” OC stud spacing, 2-stud corners, raised heel roof trusses, and ladder blocking at wall intersections.
The blower door result for this home was 439 CFM50. Without the PV system, the HERS score was 65. With the PV system, the HERS score dropped to 44.
Chatham Habitat is very grateful for the solar system donation and looks forward to more solar opportunities in the future to further improve the energy efficiency of their homes which benefits both the Partner Families and the environment!