Insulation Switch

January 18th, 2008 by Mary Schmelzer

Late last Friday, we spent some time gathering information about AirKrete for the local building official. The insulators were ready to come up on Monday morning and install the stuff, but waited for approval before coming.

Meanwhile, we had Gary and Matt put up vapor retarders and vent chutes to accomodate the Airkrete foam. Everything was ready.

The building official was at seminars all day Monday, but reviewed the data between sessions. At 4:15pm, I called him to find out what he thought. He approved the insulation, so I called the installers and conveyed the good news.

That’s when the clinker clunked. The weather forecast looked too cold (it’s barely above 0 as I type this.) Airkrete is a cementitious foam, meaning that its base is cement. Cement needs to hydrate and cure, and relies on water for hydration. As I understand it, improper hydration could cause the product to slump, or sag within the wall cavity leaving gaps that would need to be repaired. Also, the hoses and equipment are subject to freezing, which can damage them badly.

They estimated a week to install the foam, followed by a week of curing time before the sheetrock could go up. Given the forecast, that would mean a three week minimum delay and the possibility of slumping.

We called Heim Insulation and had them price Icynene foam and cellulose. Their crews were available and the price seemed fair. Today they are installing Icynene in the walls and cellulose over 3″ of Icynene for the ceilings.

Although we didn’t get Airkrete, I believe we will have excellent performance from the new insulation. We saved the fuel of getting the Airkrete installers up from Iowa and the energy we would have spent keeping the uninsulated house from freezing while we waited for warmer temperatures. This should offset the petroleum usage in the icynene.

Airkrete is a bit unknown in these parts, and we spent considerable time learning about the product and studying its properties. I do believe it is “greener” than icynene, but it just wasn’t meant to be on this house. That being said, there is a cavity in the kitchen walls that could be filled with Airkrete if it warms up before the siding is on…

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