Insulating basement HVAC Ducts


Old 08-06-08, 08:45 AM
Thread Starter
Join Date: Apr 2008
Posts: 13
Received 0 Votes on 0 Posts
Question Insulating basement HVAC Ducts

I would like to insulate my HVAC ducts in my house. They are
6" diameter. I have a lot of 16" wide left over R13 paper faced insulation from other wall jobs. Can I use this to insulate these ducts by simply stapling it up into the joist space creating an insulated air pocket around the ducts with the floor joists and insulation? Will the vapor barrier on the insulation be a problem? Can I also wrap the big rectangular feeder ducts coming off the furnace with the same insulation?
Sponsored Links
Old 08-06-08, 10:28 AM
airman.1994's Avatar
Join Date: Dec 2005
Location: VA
Posts: 5,795
Received 8 Votes on 8 Posts
If your basement is conditioned there is no need in insulating them. Duct wrap is the only good way to insulate duct work. You should purchase a duct wrap stapler and use the string tape that will match the insulation.
Old 08-06-08, 02:41 PM
Thread Starter
Join Date: Apr 2008
Posts: 13
Received 0 Votes on 0 Posts
My basement is not heated. It's unused space. I know duct wrap is good but I already have these fiberglass R13 rolls and the R rating is higher than duct wrap. I don't doubt that this fiberglass would insulate the ducts nicely, but I am concerned with possible condensation somewhere in the small air space I would create around the duct if I staple the insulation to each side of the floor joist and pack it up against the duct.
Old 08-13-08, 07:22 PM
Join Date: Jan 2008
Location: Texas
Posts: 11
Received 0 Votes on 0 Posts
Every single thing I've read about insulating existing ductwork says to wrap the ducts with insulation barrier on the outside (facing the attic not facing the duct.) And all the the pre-fabbed duct wrap I've seen has foil on the outside.

Why would you want air space around the ducts? The whole point of insulating ductwork is to keep the conditioned air inside the duct.

I wrapped mine tightly with thick foil faced fiberglass insulation and taped the seams together using high heat rated foil tape. This was after applying mastic to all the seams and joints.

Doing that, sealing all the attic air penetrations I could find as well, and blowing in more insulation was well worth the time and energy spent. I don't even want to think about how much conditioned air was escaping into the attic before, but from the drop in the electric bill it must have been a considerable amount.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: