Insulation R-Value and Humidity
Some types of foam insulation are blown with heavy gases such as chlorofluorocarbons (CFC) or hydrochlorofluorocarbons (HFCs). However, over time these gases diffuse out of the foam and are replaced by air, thus reducing the effective R-value of the product. This has been shown to have even worse effect when the insulation becomes wet, sometimes lowering the R-value by up 25% or more.
Insulation manufactures definitely avoid emphasizing this type of thing in their literature – finding any data on this is difficult. Finding data on claimed R-values for new insulation installed under perfect conditions is trivial, in fact they beat you over the head with it. As bad as the lack of data is for foams – it’s infinitely worse for blow in insulation products.
I would really like to see a chart showing the R-value per inch for both blow in cellulose and fiberglass showing what happens as the moisture level increases and the temperature drops at various blow in densities. It’s well known that cellulose can adsorb up to 135% its own weight in water. Cellulose is commonly called a moisture buffer these days. What happens to the R-value in humid climates after this so-called buffering? What happens with fiberglass? Where’s the data?
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