UPDATED with an expert opinion from Bruce King
Writing from Glacier, Washington, Karen Bean faces a home-building dilemma that confronts many thousands of people: what’s the best way to insulate the walls of her new house on a modest budget?
She has $150,000 to spend on the two-bedroom, two-bathroom house, which she plans to build on a foundation originally intended for a traditional house. Although the concrete-block foundation is well made, it’s not necessarily well matched to the double 2×4 walls she’s hoping to use.
“Is double wall with blown fiberglass insulation worth the extra cost?” she asks in her Q&A post. “And can it be done on an already laid concrete block foundation? Or is there another equally warm option that I just don’t know about?”
Bean’s quandary is the subject of this week’s Q&A Spotlight.
Suggestions for a truss wall system
Bean helps clear up some confusion over exactly what climate zone Glacier is in; it turns out that the site is relatively cold. Glacier is about 30 miles east of Bellingham, WA, and usually sees about 7,000+ heating degree days per year.
And that, says Robert Riversong, makes it a good candidate for a Riversong Truss house, an energy-efficient design he’s been building in New England for many years. The 12-in. thick walls are filled with dense-packed cellulose, not fiberglass.
“I typically build with locally sourced, green, rough-sawn lumber, no exterior sheathing and horizontal shiplap siding, with the Air-Tight Drywall system as the interior air barrier,” Riversong writes. “This makes a highly breathable, highly insulative (R-45) wall with almost no thermal bridging, and requires no more lumber than a conventional 2×6, plywood sheathed house. And it’s about as green as can be done with conventional materials.”
Rob Harrison is using…