A low cost alternative to “flash and batt” insulation?
Hello to all –
I’m trying to find a cost-effective solution to insulating the exterior walls of a 1900 vintage 2-1/2 story house. I’m located in Omaha – climate zone 5. I had originally thought that using flash and batt insulation would be an effective way to form an air infiltration barrier and provide an R-value higher than available using 3-1/2 fiberglass batts. However, the cost of 1-1/2″ of spray closed cell insulation was a concern.
I now wonder if using EcoSeal sprayable caulk and squishing 6″ of fiberglass insulation into a 4″ cavity might not provide most of the benefit of “flash and batt” at a substantially lower cost.
Mark Holladay, in his posting on September 23, 2011, “Air Sealing with Sprayable Caulk”, was quick to point out that sprayable caulk was not the same as flash and batt insulation. Then, too, in his post and Q&A of July 10, 2009, “Installing Fiberglass Right”, Martin explained that squishing fiberglass insulation does, in fact, increase the R-value in a wall cavity.
The house I’m renovating is, quite simply, just old. It would never be considered a historic renovation. So my goal is provide the best insulation I can without the high cost of high-performance insulation. The plaster walls have deteriorated and I am in the process of removing the plaster and lath from the exterior walls.
My plan would be create an air barrier using EcoSeal to seal the edges of the studs AND each gap of the exterior sheathing (nominally 6″ boards), then compress 6″ of unfaced R-22 into the 4″ cavity. Hopefully the compression would yield an R-value of 17 or so.
Since I can apply both the EcoSeal and insulation with out hiring a specialized contractor, it seems to me that this combination would provide an adequate and relatively inexpensive insulation solution for a 110 year-old house.
Your comments and feedback are solicited.
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