11:44AM | 03/21/04
Member Since: 05/18/02
12 lifetime posts
I recently built a large home on Long Island. MY HVAC contractor installed a large central return for each zone and placed the digital thermostat for that zone near each return (there are 5 zones). When I questioned if there should be a return in every room, he told me that the large central returns are the most efficient way to install the returns because they move the air the best. Is this correct? In addition, does it pay to insulate the ductwork that supplies my 2nd floor, and if so, what so I use to insulate them? The air handlers are located in my unfinished attic.

plumber Tom

02:33AM | 03/22/04
Member Since: 05/10/03
801 lifetime posts
Somebody please correct me if I'm wrong, but the size of the supply (main trunk line) will determine the size of the returns. You need a certain amount (Cross sectional area)for proper heating and cooling. Are the upstairs rooms cooling? By all means you need the insulation on the supply trunk. A great amount of heat is wasted, especially in a cold attic.


01:45AM | 03/23/04
If you have air handlers in the attic, it is impertative that the duct be insulated. Return air duct is so commonly undersized to save on money. That is the ONLY reason whey contractors skimp on it!!! It absolutly has nothing to do with effeciency. Your unit can only supply what is returned. Keep that in mind. There should be a return air in EVERY room returning the same amount that is being supplied. Period. This is what helps effeciency.


12:43PM | 03/23/04
Member Since: 05/18/02
12 lifetime posts
What is the best product to wrap the air supply trunks with? Is it necessary to insulate the return trunks as well?


02:43PM | 03/23/04
The most common form of duct insulation is trade named "Duct Wrap". Available from Owens Corning or Johns Manville. It is simply foil/kraft faced insulation in 100' rolls that is 1.5" thick and 5' wide.

Try here:

Be sure that all the duct seams are taped with duct tape before insulation. They make special tape for the insulation. Let me know if you need any further help.

Good Luck


04:12PM | 03/23/04
Member Since: 05/18/02
12 lifetime posts
Thanks for the reply and the link to the sites. I have a question about sealing the ducts before warpping them with the insulation. I read on the websites not to use duct tape because the adheasive loses its stickyness and it comes undone. Is there a different type of tape for this purpose? What else would you recommend to seal the trunks with that I could put do myself?


04:34PM | 03/23/04
There are a couple of products you can use besides duct tape to seal duct. They are duct mastics that are water based and easily applied to seams with a paint brush.

Here is one:

Also, the tape used for the duct wrap itself:

Let me know if you have any other questions.

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