Sealing Ducts in damp crawl space
 

I have all of my ducts and furnace in a "damp" crawl space. To prevent
moisture from coming into the house via the HVAC system I want to seal my
ducts as much as possible and would like some advice on the best way to do
this. I did have someone seal all of my return ducts with mastic and was
wondering if it made sense to do the same with the supply ducts. Is there a
better way, etc?

Any advice is appreciated.

George

PS.. BTW.. I did put down 6 mil plastic on the floor of the crawl space to
help bring down the moisture it the area.. I also plan on putting a
dehumidifier down there with the goal of drying the area somewhat.

I did have someone seal all of my return ducts with mastic and was
wondering if it made sense to do the same with the supply ducts

Why bother? When there's air flow in the ductwork, it's under positive
pressure, hence no air infiltration. When air flow stops, the pressure iside
and out are the same, so still no infiltaration. HTH

Joe

If you're talking about the seams where pieces of duct connect to one
another, I'd use exterior silicone sealer, in whatever color is easiest to
see while you're working. Buy a product that doesn't harden completely.

"George Sambataro" wrote in message
...
I have all of my ducts and furnace in a "damp" crawl space. To prevent
moisture from coming into the house via the HVAC system I want to seal my
ducts as much as possible and would like some advice on the best way to do
this. I did have someone seal all of my return ducts with mastic and was
wondering if it made sense to do the same with the supply ducts. Is there
a
better way, etc?

Any advice is appreciated.

George

PS.. BTW.. I did put down 6 mil plastic on the floor of the crawl space
to
help bring down the moisture it the area.. I also plan on putting a
dehumidifier down there with the goal of drying the area somewhat.

George Sambataro wrote:
I have all of my ducts and furnace in a "damp" crawl space. To prevent
moisture from coming into the house via the HVAC system I want to seal my
ducts as much as possible and would like some advice on the best way to do
this. I did have someone seal all of my return ducts with mastic and was
wondering if it made sense to do the same with the supply ducts. Is there
a
better way, etc?

Any advice is appreciated.

George

PS.. BTW.. I did put down 6 mil plastic on the floor of the crawl space
to
help bring down the moisture it the area.. I also plan on putting a
dehumidifier down there with the goal of drying the area somewhat.


Frankly I don't think you need to. There would be little air exchange
between the ducts and the area around them and almost all of that will be
from inside to outside, unless they are return ducts.

If you want to you have only two choices. The best is duct cement or
calk. It is made just for that. You might find it a little difficult to
find, but the pro places will have it. Next best is the metal tape, that
looks a little like duct tape, but it is shinny and has a peel off layer
over the adhesive. Don't even bother wasting your time with "duct" tape.
It is great stuff for some things, but not this one.

No matter what you may use, be sure to clean and dry the surfaces first.

--
Joseph E. Meehan

26 + 6 = 1 It's Irish Math

George;

You can seal ducts using approved sealant that meets the 181B standards. If
you use a mastic that is not generally intended for ducts, you may be
compromising them depending on the type of duct your working with. Also,
some mastics really stink.

You can find information for proper residential duct assembly by following
this link:

www.flexibleduct.org

If your ducts are solid sheet metal, than the seams should be sealed using
the 181B sealant, Screws and tape. You can find reputable HVAC contractors
who can test your duct to see what percentage is leaking....

http://www.comfortinstitute.org

http://www.comfortinstitute.org/consumer/report3.htm

--
Zyp
"George Sambataro" wrote in message
...
I have all of my ducts and furnace in a "damp" crawl space. To prevent
moisture from coming into the house via the HVAC system I want to seal my
ducts as much as possible and would like some advice on the best way to do
this. I did have someone seal all of my return ducts with mastic and was
wondering if it made sense to do the same with the supply ducts. Is there
a
better way, etc?

Any advice is appreciated.

George

PS.. BTW.. I did put down 6 mil plastic on the floor of the crawl space
to
help bring down the moisture it the area.. I also plan on putting a
dehumidifier down there with the goal of drying the area somewhat.

I was thinking there might be some kind of venturi effect where air flow
will tend to pull in air from around it.


Why bother? When there's air flow in the ductwork, it's under positive
pressure, hence no air infiltration. When air flow stops, the pressure
iside
and out are the same, so still no infiltaration. HTH

Joe