Main Duct Insulation? Good or Bad Idea?

[scottb82]

I recently purchased a new home (2,000 sqft) in Clev. Ohio area and over the past winter I noticed that the bedroom on the second floor (furthest from the heat source) never seems to get warm enough. In the basement were the furnace is, this is the last duct off of the main trunk. The furnace itself is on the far left of the basement and the duct in question is on the far right. I have played with the dampers and registers in all of the other rooms but can't seem to increase the warmth in that bedroom. Eventually, I will have the basement finished and will be building a sofit around the main duct.

My question is, Can I wrap the main heat duct with insulation to keep it warmer (and reduce noise)? I have been told that I shouldn't because in the summer this would cause condensation and ruin the sofit that will be installed. But, I see special foil insulation sold just for this purpose?

On a side note, I have insulation bats that the builder installed on the top 2/3rds of the basement block (per city code) that I have removed during the finishing process (had to remove it once I started framing up the walls for the rec room). If I can insulate the duct... can I use the bats that I removed from the walls? They have a plastice vapor barrier of sorts.

[speedracer]

We insulate cold ducts all the time to prevent condensation. When a cold duct is exposed to moist air, the outside of the bare sheet metal will sweat. Insulation applied to the duct should have a vapor barrier on the outside of the insulation to prevent moisture from infiltrating and finding the cold surfaces. Seams are sealed air-tight.
I don't really think it will help you much, but it couldn't hurt. Look for restrictions in the branch, like elbows, offsets and transitions, and increase the size if possible.
Closing down some on all the registers in areas where it's comfortable, especially where the stat is located will do the most good. Look for poor insulation, drafts, and heat loss from the cold room.

[wayner211]

Better insulate it before you build a soffit around it or it will swet and drip water everywhere. You can't hurt anything by insulating it. It does sound like you need to get someone out to check out the ductwork just to make sure it is sized right.

[docholiday]

I agree insulation is always good but I dont think it will help your problem, I suspect poor duct design. You may just consider a booster fan as much as I hate them.