On Tue, 25 Oct 2005 17:30:39 GMT, "Dave" wrote:

Thanks for great ideas everyone.
Some of you mentioned that I use "Insulated" flex pipe for a long run. I am
not sure if I have seen this pipe. The ones I see at the hardware store are
the regular flexible plastic pipe for bath fans. If I use a 4" PVC pipe,
would this provide enough insulation??? and why do I need to have insulated
pipe to begin with?

Dave.

Most of the big box stores carry it, at least here in OH. 20 or 30
feet of it come smooshed into a box about 3 feet long. The duct
itself is like the plain flexible type you have seen, but is wrapped
with fiberglass insulation and thin plastic.

In cold climates, the attic will be cold in the winter. The warm
moist air in the duct will condense against the cold sides of the duct
and water will puddle in the duct. This collects dust and often
provides a place for mold to grow. Sloping the duct so water can
drain out will help, but because the duct is not perfectly smooth
inside, it is still not ideal.

Plain PVC pipe won't prevent the condensation, but does tend to drain
better.

If you live in a warm climate it can work in reverse in the summer,
with warm moist attic air condensing on the outside of the duct as it
carries cooler air conditioned air. So either way, using the
insulated duct is a good idea.

HTH,

Paul