Our wall example is part of a zero-energy single-family house built for the tenant farmer of an organic farm in rural Connecticut. The owners wanted a sustainable, healthy, and self-sufficient home. Using REM/Design to analyze the cost-benefit trade-offs, we designed the envelope to keep the home's energy demand low enough that heating and cooling can be supplied by a 1-ton Mitsubishi Mr. Slim mini-split heat pump. That left room in the budget for rooftop solar electricity panels with enough capacity to operate the house at net-zero annually.

The wall is framed with 2x4 studs 16 inches on-center and is sheathed with Zip System OSB panels taped at the joints for airtightness (A). The stud bays are filled with open-cell spray foam insulation. (The original spec was for blown cellulose, but the local insulation contractor charged less to install foam.) Over the sheathing, we applied two...

or Register to read the full article.