Expert: Dave Johnson - 6/8/2008

Question
I plan to close in my deck to make a 3 season sunroom. Floor is 2X10's and the contractor recommends netting the underside of the joists and installing Nu-Wool cellulose insulation. Deck is 30 inches above the ground. My concern is moisture and or rodents getting into the insulation. What do you think of installing ridged foam over the existing floor and then the subfloor over that?

Answer
Hi Greg,
I also would be concerned about rodents.
If it were mine, I would attach 2"x2"'s to the inside bottom of both sides of the joists and install 2" foam pressed down to them. Any voids can be fixed with some spray foam ins.
After that, you could even add more insulation of any kind...I think a foil faced foam facing UP would be good, too.
( don't use fiberglass, its nothing but a @#$% filter.)
Best of luck,
Dave