Type of Insulation/Infiltration

Mike T., Swampeast MO

Interesting. In enclosed cavities at least, the type of insulation seems to have little/no effect on air movement/infiltration in that cavity.

I must admit I had "bought into" the idea that fiberglass allowed much more air movement than cellulose, etc.

Unfortunately it doesn't seem at address this in places like unfloored attics with insulation sitting on top of the ceiling but utterly exposed to the air in the attic.


http://www.naima.org/releases/nahb.html

PS. HOW do some of you manage hyperlinks here?

Bob W._2

That might be true for a quality high density fiberglass batt .

installed correctly (no compression; no gaps) in a stud wall, but the most current research indicates that convection currents in fiberglass in attics can seriously lower the R value as the temperature drops. Topping the fiberglass with as little as 3" of cellulose can stop the convection. As far as wall insulation is concerned, I believe there are tests that have done with identical structures that have shown cellulose to do a superior job. Of course, cellulose has its down sides as well; better have a good vapor barrier for starters.