# how to secure insulation to flute?



## wantboost (Jun 8, 2013)

i just installed a gas fireplace. i was wondering how can i secure fireproof insulation to the flute?

thx


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## begreen (Jun 8, 2013)

Do you mean the flue? Normally this is not required with a gas flue.


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## wantboost (Jun 9, 2013)

yes flue. i wanna insulate it just to keep draft down etc???


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## DAKSY (Jun 9, 2013)

wantboost said:


> yes flue. i wanna insulate it just to keep draft down etc???


 

What did you install, where did you install it & how is it vented? You will have to provide pics or a more detailed description in order for us to help you...


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## wantboost (Jun 11, 2013)

its installed into a existing wood burning fireplace. iinstalled a lennox mpd vented out the back. i wanna insulate the flue opening.,??


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## coaly (Jun 11, 2013)

This is a direct vented unit. The inner pipe is the exhaust, cooled by the incoming air between the inner and outer pipe. There is a 3 inch clearance to combustibles at the top of pipe, 1 inch sides and bottom. Insulation on the outside of the outer pipe would not keep the inner pipe hotter like in a conventional chimney or liner and have no beneficial effect.
  Keep in mind the reason for the horizontal run and vertical rise required is calculated to maintain the exhaust draft needed to allow heated gasses to exit the combustion chamber inside the inner pipe.  (see table in instructions) This rising of combustion exhaust is what puts the sealed combustin chamber in a negative pressure area allowing atmospheric air pressure to push into the intake area between pipes, supplying oxygen to the burner. Keeping the intake air hotter due to insulating the exterior of the vent pipe would have little to no benefit. Matter of fact, the hotter intake air would be expanded having LESS oxygen molecules per square inch than colder denser air. This would cause the mixture to be richer. As for "chilling" the firebox, the incoming air is going to be preheated by the exhaust inner pipe by the time it gets to the appliance anyway.


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## DAKSY (Jun 11, 2013)

wantboost said:


> its installed into a existing wood burning fireplace. iinstalled a lennox mpd vented out the back. i wanna insulate the flue opening.,??


 

So you put a gas burning fireplace into a wood burning unit? Is the wood burner masonry & site-built or or is a ZC factory-built unit? I suppose, either way, if you can get into the woodburning flue, you can just grab some unfaced fiberglass insulation & jam it up in there. Make sure it's tight enough to stay on its own, otherwise, you'll need plumber's strapping or wire to secure it. To do the job correctly, you should also insulate the top of the chimney & cap it off with an aluminum plate & silicone it in place...That'll keep critters & water out.


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## wantboost (Jun 12, 2013)

fireproof insulation? should i insulate the bottom of the flue also?


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## DAKSY (Jun 12, 2013)

wantboost said:


> fireproof insulation? should i insulate the bottom of the flue also?


 
Unfaced fiberglass top & bottom...


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## wantboost (Jun 14, 2013)

whats unfaced fiberglass?


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## DAKSY (Jun 14, 2013)

wantboost said:


> whats unfaced fiberglass?


 
"Unfaced" fiberglass is insulation. You don't want "Faced" fiberglass in that situation. It has a paper backing., Paper is flammable.


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## s!MON (Aug 25, 2013)

i'm surprised! Surely only a qualified Gas installer should be installing a gas fire.


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