Insulation for 4" exhaust fan duct - available?

I'm installing a bathroom exhaust fan, and I want to insulate the exhaust duct. I'm planning to use 4" solid exhaust duct. Where can I find insulation for this 4" round duct?
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You can find fiberglass pipe wrap at the big boxes or probably a True Value or Sentry. My concern was the effectiveness of the flaps.

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Not to be a smart alec, but why do you want to insulate it?
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In areas where it is very cold and the pipe passes through an unheated attic, condensation (or ice) can form on the inside of the pipe. This happens because the flap at the fan doesn't usually close 100% and allows some inside air to pass even when the fan is off. If ice forms, it will eventually melt and might probably drip from the fan. I've had it happen.
HeatMan wrote:

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Okay, that makes sense. Around here, it doesn't get THAT cold....

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Why not use the pre-insulated flexible duct? The big box stores around here all carry it. Unless your run is really long, the extra losses won't be an issue on the push side of the fan, and it will be quieter.
HTH,
Paul
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On Wed, 22 Jun 2005 21:03:21 -0400, Paul Franklin wrote:

I might end up using flexible duct, as the run is short. I didn't find it at the local Lowe's store however. Will check Home Depot.
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I worked for a manufacturers rep many years ago. One of the lines we carried was pipe insulation in sizes from 1/2" to 12" with various types of insulating material and several different sheaths.
If you contact Accessible Products Co. 2122 W 5th Place Tempe, AZ 85281 Phone: (480) 967-8888 Toll Free: (800) 922-5252 Fax: (480) 894-6255
they may be able to give you the name of their representative/distributor in your area.
No, I have nothing to do with Accessible Products anymore.
____________________ Bill Waller New Eagle, PA
snipped-for-privacy@comcast.net
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On Wed, 22 Jun 2005 08:09:52 -0400, Bill Waller wrote:

Thank you Bill. I'll give them a call.
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I don't know the specifics of your installation, but if at all possible, try to slope the majority of the line towards the outside vent. That allows any condensation that builds up to drain off outside the building and not back into your fan.
As for the insulation, I just put an extra layer of fiberglass batts over my vent lines in the attic space (ours vent out the gable end walls). They're probably better insulated than the rest of our house. :)
You could also wrap the pipe with fiberglass batts and use string, duct tape, plastic zip ties, or something similar to hold it all in place.
Alternatively, use long strips of insulation, and start wrapping at one end, overlapping the previous wrap by a 1/2 width or so with each turn. This would give you about twice the insulating value and no gaps in the insulation.
Anthony
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On Wed, 22 Jun 2005 13:13:55 -0500, HerHusband wrote:

I wish I could slope the duct down, but I have to route the duct about 2 feet over and 4 feet up to vent through an outside wall.
Thanks for the idea of using the fiberglass bats, that sounds like it would work quite well. Not too hard on this short run either. I might do that if I can't find 4" pipe insulation locally. So far I found only 6".
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