Duct insulation

Jim_65

We have existing exposed duct work that is located in a insulated crawlspace. Although the crawlspace is insulated I am contemplating insulating the actual plenum and supplies. The main reason is because the areas of the house that are being served by these branches are always hot in summer and cold in winter. The remainder of the home is very comfortable and the duct work is located in a more conditioned area of the home.

The house is 4 years old and this has been a issue since day one. As I mentioned it would be one thing if we experienced this when we were at design conditions. Unfortunately it occurs in this one room. I have performed the heat loss/heat gain calcs. and all of the equipment is more than capable of satisfying the loads. I may need to calculate if it is a air flow issue only to this portion of the FA system (Duct size too small?).

What is the most effective insulation for duct work available? It a foil/bubble product worth the time and money for wrapping the duct? Is that even the correct approach?

Does anyone else have any suggestions that may be beneficial?

Thanks in advance!

Brad White_9

Forget insulation, Jim

If you are not going to seal the duct first. Get some Hardcast Iron Grip or the tape and activator. Seal all the joints and seams that you possibly can. Air loss is irretrievable.

For any ductwork joints up and above the joists, inaccessible, use expanding urethane foam. Do what you can with proper duct sealant first though.

Once sealed and tested, insulate to your heart's content. 1.5" foil-faced duct wrap is a standard around here (R-5) and if outside the heated envelope, R-8.

But seal first! If you want to drive a 10% loss of air it will cost you about 30% in HP...

Jim_65

Thanks

Thanks Brad!

I noticed that all of the joints are sealed for the most part with normal silver tape but I agree that it would be beneficial for me to make it as tight as possible prior to insulation. I will proceed with your recommendations.

I appreciate your input and most of the time when I see your posts I brace myself for a good laugh. Not that your posts are not full of good advice but a quick wit and play on words type of humor is quite enjoyable.

Take care - Jim

Brad White_9

Funny thing, Jim

Here in Massachusetts, the one thing that is Verboten for sealing ducts is..... Duct Tape! Our energy code says so, right there... Realistically, yes, it does dry up and fall off but I do believe that the aluminum foil type if applied to a clean surface is far better. So....if your duct is sealed, time to wrap!

Glad I can entertain now and again

Excuse me, I have to berate the hamster....

hvacfreak

tape

There is a product avaiable that is a foil - faced heavy mastic made by " Hardcast " ( like TDC mastic with foil face ). I have taped 2 inch static med. pressure main duct joints ( round ) within seconds of pressurizing. This stuff is expensive , but makes for an easy , perfect seal. For low pressure , residential slip and drive trunk joints , I would just do the corners with this. R.E Michel no. 8H287.

hvacfreak

hvacfreak

hvacfreak

weird

Server side lag cause this ? I pressed post one time and it took forever , so I minimized browser...I don't know how to delete a post.

hvacfreak

what the ? lol

How'd that happen ? LOL

Brad White_9

Excellent product, that Hardcast Tape

Seems you really, really like the stuff!