# Drafty Gas Fireplace



## Robert620 (Jan 7, 2017)

Just installed a new gas fireplace. There is a lot of draft coming thru the exterior box of the fireplace around the fire box, there are a number of perforations around the sheet metal for electrical and gas, etc. I used metal tape to try and seal the holes on the exterior of the sheet metal, but no luck there. I believe the adhesive just gave way with a bit of heat. The fireplace is in a chase about 5' X 2' built on the exterior of the house that runs floor to ceiling. The chase is not insulated or sealed. is there any way to seal the fireplace exterior box, or do I have to seal and insulate the chase to stop the draft?


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## DAKSY (Jan 9, 2017)

Sorry to tell you, but you need to insulate. 
I taped the exterior seams & holes of the firebox with aluminum tape 
BEFORE it was loaded on the install truck.
I use R-19 Kraft faced around the chase walls,
& built a sheetrock deck above the unit & insulated that, as well.
There should be insulation under the floor, too.
The interior chase wall should be sheetrocked after it's insulated &
I also tape or caulk EVERY seam in the sheetrock, 
If you vented off the top, you need to seal the gap between the vent 
& firestop in the sheetrock deck.
The main problem comes from the fact that you have a metal box sitting in an 
unheated chase. Even with all the sealing & insulation, if the unit isn't
burning, the box will get cold & you will get a draft from the warm air inside
your home hitting that cold metal & getting cooled. It will then flow into the top of 
the unit, hit the (COLD) heat exchanger, drop behind the firebox & exit thru the 
valve cavity as a cold draft.


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## Robert620 (Jan 10, 2017)

Thanks for the reply!
So the next question would be how and what to use to seal around the vent cap. There is still a lot of air able to get thru there??? Can it be insulated as well? Is there some high temp insulation? I have a horizontal/sidewall vent.


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## DAKSY (Jan 10, 2017)

You can use tape gasket. It's the same stuff that's used on wood stove glass.
3/4" wide with adhesive on one side. Get about 4 feet of it, so you can wrap it twice.
Use your high school math - pi x the diameter of the pipe - to figure out what you'll
need to go round it one time, & then double that to make sure you get a good seal.


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## Don2222 (Jan 14, 2017)

It you do Roxul 100% fire proof insulation then no need to Sheetrock


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## DAKSY (Jan 29, 2017)

Don2222 said:


> It you do Roxul 100% fire proof insulation then no need to Sheetrock



Even if you can get rigid Roxul, you will STILL need seal the seams. 
Not sure of the cost, but I'm thinking R-19 & sheetrock are cheaper than Roxul.


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