How to Stop a Cold Draft Around Your Gas Fireplace

by Michael on January 21, 2011 · 3 comments

Ever since we moved into our house in 2006, we’ve noticed a cold winter draft around the gas fireplace in our living room. During the winter, we can actually feel a light “breeze” through the vent above and below the fireplace. Very annoying.

Diagnosing the problem

We actually had a fireplace guy come out to look at it and he couldn’t see anything wrong. I suspect that the installer didn’t insulate the chase properly, and that we’re getting air intrusion behind the fireplace that works its way down to the vents.

Unfortunately, we’d have to tear out the marble around the fireplace to get the insert out and check/fix the problem. In the long run, we may go that route. But in the short run, I want to block that cold draft.

I’ve considered sealing it off with plastic, but we enjoy having an occasional fire, so we really need something that can be easily removed and replaced. After giving it some thought, I came up with a very simple and effective solution.

Blocking the draft with foam

I started by measuring removing the vents above and below the fire box and measuring the openings. The vents themselves just hang on a couple of pegs so it only takes a few seconds to pop them off and put them back on.

The firebox itself is 42 inches wide, with a 4.25 inch vertical gap above it and a 6 inch vertical gap below it. With that information in hand, I headed to the local fabric store in search of some thick foam padding – the same sort of foam that they use to make egg crate mattress pads, only thicker.

I ended up buying a 42 inch long section of 2 inch thick x 24 inch wide foam “upholstery padding.” It cost $30/yard, so I ended up spending about $35. I could’ve saved a bit of money by getting a shorter section and using more than one piece to span the 42 inch width, but I wanted to do it with a single piece.

When I got home, I marked off a 4.25 inch width and cut it off. Note that a serrated bread knife work great for cutting this type of foam. I then marked off a 6 inch width and cut it off, as well.

From there it was just a matter of plugging the gaps. I expected to have to cut a few slots and notches into the back of the foam to make it fit over the irregularities along the edges of the openings, but I was able to just squish it into place.

cold draft gas fireplace

The end result (pictured below) was even better than I expected. The foam fits snugly and makes a nice, tight seal. At the same time, it’s very easy to pop it out and put it back in if we want to have a fire.

cold draft gas fireplace complete

A few notes…

For starters, we keep the gas turned off (and thus, the pilot light extinguished) when we’re not actively using the fireplace. If we kept the pilot light burning, it wouldn’t be safe to seal the gaps like this.

Second, we’re very careful to remove the foam inserts from both the bottom and top before having a fire. The bottom one is a no brainer, as that’s where our gas valve and starter are located, but we still have to remember to pull the top one out.

Finally, we never put the inserts back in until well after the fireplace has cooled down. And again, we always shut off the gas, thereby extinguishing the pilot light before sealing it back up.

{ 3 comments… read them below or add one }

Max December 10, 2013 at 10:37 am

Thanks for the write-up. I’ll have to give this a try. You appear to have the same insert that I have and it gets really drafty this time of year. I can’t tell from the pictures but do you have any glass covering the front of the fireplace or is it open? Mine is open and I’ve often wondered if it is supposed to have glass or some type of closure across the front of the logs that might control the drafter better.


Ana January 2, 2014 at 1:45 pm

I came across this and loved the idea but can’t seem to find the foam material. Is there a specific name for it or where I can purchase it? I have a heavy draft coming from the grates and need it covered!! Please help!


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