Virginia Homeowners Build a Passivhaus on a Budget

When it came time to make a home together, Jason and Stephanie Specht wanted to build a sustainable house in Thaxton, VA which is classified as a Climate Zone 4A. Upon consultation with the representatives of Structures Design/Build company they opted for a Passivhaus design. The custom optimized Passivhaus design created by Structures Design/Build allowed the Spechts to achieve cost parity with traditional construction.

The completed Spechts Passivhaus home has a living space of 1808 square feet and cost $150 per square foot to build. This price includes septic and well work, as well as some general site work. The Spechts home went on to receive the PHIUS+ certification and has a HERS rating of 38.

The house is built on a modified raft foundation, with the slab insulation made up of two staggered layers of horizontal EPS foam board (R-18) under the entire slab, and molded EPS forms at the perimeter. The Structures Design/Build team added a thickened edge to the raft foundations, which resulted in several positive impacts. First it allow for the majority of the slab to be insulated with standard sheets of EPS foam, which is easy to get, while the only proprietary piece of EPS foam was the integral footer. Another benefit came from the fact that the slab could be poured at a standard thickness, which meant that less concrete was needed for the foundation. This resulted in lower cost and lower embodied energy.

The wall air barrier was created using the Zip System sheathing and tape. To ensure complete airtightness and to eliminate any leakage the team performed blower-door tests at several stages of the construction process. They performed the first test when the sheathing was first sealed and before the window and door openings were cut. Through this process they were better able to quantify and isolate the leakage paths, and to determine the effectiveness of other air barrier components, such as utility perforations and window frames.

The wall structure is made of 2

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