[svaic00]

Hello,

I am in the process of finishing my basement, and I wanted to insulate the main trunk line of my duct work. The duct is 10" tall by 20" wide, and is attached on the underside of my I-joists, attached with hangers every few feet. Before I insulate I will check all the connections and brush on some mastic, along with check the existing foil tape over the seems.

My question is with regards to insulating the actual duct. Are there products out there specifically for insulating a box duct? It will be easy to insulate three sides of the duct, but the top can only be insulated between the joists, since top of duct and bottom of joist are pretty much butt up against each other. I was not sure if I should just buy batts of fiberlgass, and wrap tape around it to hold it in place, or if they make some kind of wrap for it. Should I also insulate the 6" diameter supply lines?

One article/video I found talked about insulating ductwork. It stated to use 1/2" foil faced polyisocyanurate and use that on the sides and bottom of the square trunk. Just tape the foil face to the trunk, and then use R-13 fiberglass on top of the trunk and then also use R-13 fiberglass and wrap the supply lines. Does this sound like a good way to insulate the trunk?

Any other info you can provide for insulating duct work would be great.

Thanks in advance,
Steve

[hkstroud]

I wanted to insulate the main trunk line of my duct work.

Why?

This duct work contributes to the heating and cooling of the area. I could see insulating for economy when the space was unfinished and unoccupied. But now that you are finishing and presumably occupying the area why insulate? You will probably be adding duct to heat and cool the space. Seems to be contradictory actions to me.