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Cold air coming in through gas fireplace

Posted by graywings (My Page) on
Fri, Dec 17, 10 at 9:15

I bought a house that had been added on to 10 years ago and during the build a gas fireplace was installed on an outside corner wall. Cold air is streaming into the room from that fireplace. I don't see a flue to close off when the fireplace is not in use.

First question: I've tried various and multiple methods to block the glass opening, but the cold air keeps seeping around my pieces of wood, masking tape and bubble wrap, so I'm going to put a much larger piece of plywood over the entire front of the fireplace and probably screw it in place. Any suggestions on additional steps to take, such as applying some insulation? Or is the plywood sufficient? I looked at fiberglass insulation, but for various reasons, would rather use some other product.

Second question: once warmer weather comes, how do I go about identifying and fixing the problem?



Follow-Up Postings:

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RE: Cold air coming in through gas fireplace

I assume you have a custom built fireplace, not a prefab that would come with an owner's manual. But sometimes even the gas logs, retrofitted in a custom fireplace, come with a manual. Check to see if there is a brand name on the gas logs. If you find one, check to see if they have a website. sometimes owner's manuals are available as pdf files for downloading.

Aside from that, I suspect that there is somewhere in your firebox an air intake opening to feed the fire, so that it does not consume too much indoor air. These are sometimes hard to find. Check the outside wall. It might be there. If you find it, you should close it when you do not use the fireplace and open it only when you make a fire. Ideally, it should be located where it is easy to open and close.

The kind of gas logs you have is always going to be drafty and inefficient to some extent. If you want a really efficient, ultrasafe, state of the art gas unit, you should consider installing a direct vent unit. There are many brands on the market. They costly, but really much finer than the unit you have.


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RE: Cold air coming in through gas fireplace

Thank you so much, Haus_Proud. Your response prompted me to get in there with a flashlight and look around. It turns out there is a flue and there was a C-clamp on the flue closure, keeping it wide open. I'm thinking that either someone had trouble keeping the flue open when in use or it was a misguided safety effort for when the house had been unoccupied and for sale.

I found a Heatilator installation manual in the back shed when I moved in, but I can't find any evidence that my fireplace is a Heatilator.

There is still a chill around the fireplace, but it's a lot better than it was.

Again, my thanks!


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RE: Cold air coming in through gas fireplace

So now I have goggled C-clamp on flue cover and find a reference to it being a code requirement. It's a moot point for me because I have the gas line shut off, but my goodness, that seems like a waste of energy.


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RE: Cold air coming in through gas fireplace

The reason that c-clamp is in place is to prevent you from closing the flue and creating a "ventless" gas logs system. They are disallowed by the building codes in many communities and are a health and safety hazard because they consume oxygen in the indoor air and do not exhaust the fumes from the gas combustion. Consumer Reports in their website used to have a 2-3 page story about gas logs. As I said previously, direct vent is the way to go, the optimal answer, but it will cost you. If you do a search on direct vent in this forum, you will find out more about it, possibly more than you care to know.


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RE: Cold air coming in through gas fireplace

I have the same problem, and I have put foam into the flue opening to no avail. The marble seating in front of the glass doors is too cold to sit on. I had thought that maybe the builders didn't insulate around the outside of the chimney. I'm gonna check into what Haus Poud recommended with the direct vent fireplace. Geez, you have a home built and this is what you get. It seems like the more you pay the less you get.


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RE: Cold air coming in through gas fireplace

Hannah, get a flashlight, open the doors to the fireplace and look up. Find the C-clamp and move it up and down and you will see that you are moving the damper cover which it is attached to. And you will see the flue that's letting all the cold air rush in. Remove the C-clamp and close the flue completely. While you are at it, look around for the bar in the front of the fireplace that manually opens and closes the damper.

That stopped the draft at my fireplace, but the front face of the fireplace and wall surrounding it were still cold to the touch. So, I started by covering the glass, then went bigger to cover the brick surround. Now I have the entire face of the fireplace covered.

I don't know what the long term solution is, but this is the solution until winter is over.


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RE: Cold air coming in through gas fireplace

This is what I have found with this problem. It took me forever to figure it out. The air is coming in throught the exterior wall, stay with me here. There are two pipes that run through the wall, one is small that handles the flue gases from the gas stove. The other is a larger 6-8" pipe that surrounds the smaller flue gas pipe. tha larger pipe goes throught the wall and most to all HVAC guys cut a way to big hole in your exterior wood wall. The guys then come a brick, side or whatever over the wood exterior tight to the larger pipe....so it looks nice. But when the wind blows, really noticeable with brick (because of the 3/4"air space between the brick and wood wall) builds up pressure between the brick and the wood wall. The air comes in through the large, unsealed hole that is left from the pipe going through. This air is direct to the surrounding area behind the fireplace and comes out through any vent (usually the lower grill) making the floor icey cold. Putting a bag or plastic over the box outside does nothing. The way to fix it easily is to remove the box outside, cut the larger pipe only in past the brick to expose the ouside wood wall. Seal the area around the pipe and reinstall a new short larger pipe extension. The builders contractors will only give you a runaround because they know to fix it properly is to remove the two flue pipes, and fireplace completely and seal it as it put together in steps. I hope this helps a bit and isn't too confusing.


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