FWIW, it's a myth that compressing insulation decreases its per unit depth R-value. It would do so if, in the act of compression, a gap or air gap is created. Standard insulation will gain (per unit depth) R value up to almost 50% compression. Cornings have a chart of compression values for their products.
If you go to BRANZ website http://www.branz.co.nz/cms_display.php?sn=167&st=1 and view the GUIDELINE for December 2012, you will see a note about insulation over specification, and the problems it can cause - Rediced R-value, difficulty in getting a tight fit to the framing, causing a bulge in the flexible wall underlay into a drained and ventilated cavity, and the popping of screws as the sheet adhesive is not properly compressed.
I'm sure it's not a good idea but in the small percentage which gains most benefit ie 20% or less, those issues aren't relevant. The point is that the argument about compression was really about installation eg stuffing batts into a space when they've been incorrectly sized.
Are you subscribed to our RSS feed? You can download the latest headlines and summaries from our stories directly
to your computer or smartphone by using a feed reader.
