Air Sealing/insulating Flue In Attic? - Insulation - DIY Chatroom Home Improvement Forum

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Old 06-17-2015, 01:25 PM   #1
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air sealing/insulating flue in attic?

Getting ready to put more insulation in my attic and noticed the 12in x 12in chase for the water heater exhaust flue that extends into the attic is wide open. The furnace is high efficiency and so only the water heater uses this exhaust flue.

I was reading online about code for keeping insulation so many inches away from the exhaust flue but it sounded like it was for furnaces that exhaust into it (mine just has the water heater). The flue is not warm to the touch or anything ( and is currently wrapped in fiberglass and has been for 3 decades).

Any problems with air sealing the chase with foam board and putting insulation on top around pipe or is this still a code no-no?
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Old 06-19-2015, 01:44 PM   #2
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If the flue is not introducing heat into the attic, then don't bother with it.
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Old 06-20-2015, 12:15 AM   #3
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I'd use sheet metal/fire caulking at the flue sides, pp. 19/60;

Check with local AHJ or Fire Marshall if insulating the chimney... seems it would temper the cold winter attic air from the warm exhaust gases which carry water that would condense on the pipe/flue sides quicker...

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17,000 dryer fires a year, when did you last clean the inside of the dryer near motor or the exhaust ducting?
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Old 06-23-2015, 12:10 PM   #4
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Sheet metal and itumescent caulking where it meets the chimney.
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