As Steven Knapp and his wife plan a new house in Atlanta, indoor air quality (not energy efficiency) is at the top of their priority list. At least that’s how a recent discussion on autoclaved aerated concrete began.
“We both have chemical sensitivities that make ‘usual’ building practices undesirable,” Knapp writes in a Q&A post at GreenBuildingAdvisor. “Before the market bottomed, we were planning to build a healthy house following Baubiologie practices (as much as practical) and using autoclaved aerated concrete for the structure.”
Knapp and his wife put their project on hold as they waited for market conditions to improve, and in the interim, Knapp says, local AAC installers largely disappeared. “As a consequence, we set about designing a house that would use conventional framing and as many no- or low-VOC materials as possible,” he says.
Increased residential construction is pushing up the cost of conventional building materials, and AAC contractors are back in the picture. That’s making Knapp wonder whether the 15% premium he thought he’d have to pay for AAC construction may actually be worthwhile.
“My question is,” he writes, “are you professional builders seeing big price spikes? Are they broad and large enough that I should take another look at AAC?”
While construction costs ostensibly are at the heart of Knapp’s question, the issue also touches on the merits of autoclaved aerated concrete, and that’s the subject of this Q&A Spotlight.
AAC block: higher cost, lower R-value
To GBA senior editor Martin Holladay, an AAC wall will never be able to compete with conventional wood framing on a cost basis.
“Moreover,” Holladay writes, “AAC walls have a very low R-value — most…