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winspiff
Sealing air ducts

Hello,

Has anyone had experience with sealing air ducts for efficiency purposes? This is what I have been reading, although I'm pretty sure it is an ad: http://www.vectren.com/cms/assets/pdfs/learn_about/winter_efficiency/duct_efficiency.pdf

Any experiences with it? Does it work?

Sten
Re: Sealing air ducts

Your Ductwork should always be taped, sealed and insulated, always. Duct leakage is huge as far as efficiency is concerned, you want the Air to go to the conditioned spaces and not leaking into the attic, cellar or, in the walls if your using oval duct. The only difference in putting oval in a wall is that it doesn't have to be insulated, the space between the studs that the oval is in becomes conditioned because of the warm or cold air, it won't sweat, depending on heating or A/C. The connections are still taped and sealed using Mastic or another type of Duct Sealer.
As for the returns they should always taped and sealed, you want to bring back the air from the Conditioned spaces and not the attic or Cellar. They have Systems out there now such as the Infinity by Carrier that will measure the static pressure in the Ductwork just for this reason, Efficiency. Tape, Seal, Insulate, Tape, Seal, Insulate. I can't say how important this is! Good Luck!!! :)

canuk
Re: Sealing air ducts

After reading the information within that link I couldn't help but laugh.-------- the article is somewhat ambiguous.

It stands to reason that air leakage is a negative in the distribution of a forced air system .

Yes --- if the air handler is located within the attic then all the ducting should be sealed and insulated ---- common sense.

Yes ---- if your ducting runs through an unheated crawl space it too should be sealed and insulated ---- common sense.

Why are they common sense??

The air distribution systems are not within the conditioned space.
In other words ----- putting the air handler and ducting in the cold attic and trying to distribute hot air is really counter productive.
The same applies when the same system is located in the hot attic and trying to distribute cold air.

If your ducting is within the home there is no need to insulate since it's within the conditioned space of the home.
This also is the case if the air handler and ducting runs are in a basement --- any small amount of heat transfer from the ducting ends up in the living space which contributes to the conditioning ---- it's not lost.

Anyone can buy foil tape or paint on mastic from any home supply store and for a reasonable amount of money seal their own ducting.

Sten
Re: Sealing air ducts

I disagree with your point on not insulating ductwork in a cellar, have you ever seen what happens when your A/C is on. You end up with puddles on the cellar floor from it sweating. The same goes for in an attic only you'll and up with other problems, like a wet ceiling. And either installation be it the cellar or attic when wet can cause mold. If you live in the colder climate and you have your furnace in the cellar or basement and it isn't insulated you will have heat lose, Guaranteed. I have never done a full System install be it Heat or A/C without fully insulating the ductwork, it's your money throw it out the window if you want. Good Luck!!! :)

canuk
Re: Sealing air ducts
Sten wrote:

I disagree with your point on not insulating ductwork in a cellar, have you ever seen what happens when your A/C is on. You end up with puddles on the cellar floor from it sweating.

Mine and thousands of homes that have ducting in a basement don't suffer what you describe --- because they are within the conditioned zone.

Quote:

The same goes for in an attic only you'll and up with other problems, like a wet ceiling. And either installation be it the cellar or attic when wet can cause mold.

I totally agree and said that earlier.

Quote:

If you live in the colder climate and you have your furnace in the cellar or basement and it isn't insulated you will have heat lose, Guaranteed. I have never done a full System install be it Heat or A/C without fully insulating the ductwork, it's your money throw it out the window if you want.

I do live in a cold climate and have the setup you described.
The amount of heat loss from the ducting within the conditioned space is very small --- because it's within the conditioned space.
Like i said --- it's within the conditioned space whatever little transfer from the ducting ends up in the home which adds to the general heating ---- it's not a loss.
You wouldn't be throwing money out the window.

Sten
Re: Sealing air ducts

When you say conditioned zone, do you mean space?? If your conditioning the space your main trunk is in I agree that you need not insulate. It would be the same as running the oval as I said in my first post. :)

canuk
Re: Sealing air ducts

Yep ---- we good?:)

Sten
Re: Sealing air ducts
canuk wrote:

Yep ---- we good?:)

Yep...... :)

canuk
Re: Sealing air ducts

Good stuff.:cool:

wg2
Re: Sealing air ducts

I live in very cold climate in the upper midwest. I just had an energy audit that left me so confused I can't believe I paid for it. Some of that auditor's claims were about ducts in the basement.

First, he said the unfinished basement was too cold. He said I should caulk the old windows in the basement shut. Then I should "add a heat register to the plenum of the furnace to heat the basement space." This sounded strange.

When I asked him about sealing or insulting the ducts, he said I shouldn't do it. (He never mentioned the ducts for the returns, which I gather are always good to seal/insulate.) He basically gave Canuck's answer. But of course Canuck was saying that you don't need to seal/insulate if the ducts are "basically in conditioned space." But if my basement is unfinished and unused except for laundry, do I want my basement to be conditioned?

I have several other questions resulting from the audit, mostly having to do with how to cut down on air bypasses in my balloon-framed home without creating moisture problems. But these are the questions I had relating to duct sealing. Any thoughts for a confused newbie?

Sten
Re: Sealing air ducts

1. If your supply ductwork is in an unconditioned space it should be taped sealed and insulated, if in a conditioned space they should be taped and sealed but don't need to be insulated. You want the air to get where it's supposed to go, If you don't tape and seal it can leak and lose pressure within the duct.

2. You should never put a grill directly on your supply plenum. If you want a little heat in your cellar put one in the main trunk at least 18" away from a supply run and not directly across from one. Putting a grill on the Plenum will also cause a pressure loss, the plenum also acts to make the air less turbulent.

3. Your return does not have to be insulated but should be taped and sealed. You want to bring back the air from the conditioned spaces and not the attic or cellar.

4. It's up to you if you want your cellar Conditioned or not but be aware that your Heat System was sized to a certain number of BTU's and it may not have included the size of your cellar. If not you would be stealing heat from the other rooms in your house, making your furnace run to long, not efficient.

Good Luck!!! :)

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