Hello,
My 1.5 story bungalow has a forced air heat/AC system. There are 2 bedrooms upstairs, and the ducting to those rooms runs up from the basement and then horizontally across an attic space for about 2-3 feet. I am going to be adding some insulation to the attic floor spaces (probably cellouse), and wonder how best to deal with the ducts. They are currently covered with some sort of felt-like material.
First I will remove the felt and make sure the seams are sealed well. Then I was thinking I should wrap them with some of that foil faced fiberglass duct insulation. Then I was thinking I might as well pile some of the cellous or fiberglass batts on top of them. But, wouldn’t that negate the point of foil faced insulation?
Any ideas?
Thanks,
Erik
Replies
Be careful of the "felt based" material, it may be asbetos based insulation. Is like heavy paper about the colour of concrete and flakes easily? (only check this using a tight fitting mask!!! Or have some one in to identify it.)
After the first issue is delt with and the duct have the material disposed of:
(1) clean or seal all the duct joints with foil tape or mastic sealant (I like the mastic best- consistancy of caulking that paints on with a small brush for normal width cracks, larger cracks need abit if fiberglass cloth tape) It's about $20 for a 2 qt can.
(2) Airseal around the ducts where they come up from the house. Some times i see openings of 3X16" inches where warm, moist house aoir can leak up from below and fiberglass and cellulose may slow it down but not stop it. At the same time may as well airseal the reat of the attic!!!
(3) If your ducting is/will only carry heating air and not air conditioning air, just wrap the sides and top of the duct with R12 fiberglass batts and then install cellulose up to R20-30+, if possible.
(4) if it will carry a/c air also, it will be necessary to install an airtight exterior air/vapour barrier on the duct insulation to keep the humid summer air from getting to the cool duct where condensation may occur.