Expert: Dave Johnson - 11/24/2008

Question
Older two story home. Attic floor has wide boards nailed to 2"x 4"s which support the ceilings below. A green foam installer quoted because of the "floor" nailed down he would instead spray the 2"x 6" rafter cavities (back side of roof sheeting), seal the soffit ventings at the overhang and the ridge vent, also spray foam the inside gable walls and gable venting louvers. In his proposal he stated this would be better than any "normal" insulation technique. ie fiberglass or cellulose.
I think he is just trying to "sell" foam and would ruin the house. There would be no venting and moisture would be trapped. Is this a new and better method that the foam guy is selling?    Note:I installed all new roof ply, weather and ice shielding, 40 yr shingles, rebuilt the chimney with new bricks, and lead flashing one year ago

Answer
Hi Harry,

Not a good idea, I think he didn't want to get involved in removing the boards.
Option 1: fill the voids between boards and ceiling as best you can, and add rigid foil faced foam to the floor, then cover foam with new sheathing.

Option 2: Remove boards, add blown cellulose, then foam, then replace boards or new sheathing...

Best of luck,

Dave