Insulation for 4" exhaust fan duct - available?

[Lee (archive)]

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?

 

[New Improved - N F John]

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.

 

[HeatMan]

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?.

Not to be a smart alec, but why do you want to insulate it?

 

[Art Todesco]

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.

 

[HerHusband]

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?

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

 

[HeatMan]

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

 

[Paul Franklin]

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

 

[Lee (archive)]

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

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.

 

[Lee (archive)]

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

Thank you Bill. I'll give them a call.

 

[Lee (archive)]

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

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".

 

[K Ruck]

I just bought a box of insulated 4" flexible duct at Menards (in Michigan) I think it was 25' for about $10. compared to my original plan of using solid duct, I'm _much_ happier, because I found out I had to take it up into the attic, then back out a eave (down-facing vent) which would have been a nightmare to make and insulate in tight quarters. It left me enough to do my other bathroom's vent when I get to it, and I'll probably have leftover to boot.