Insulate wood-burning fireplace

We recently moved into a home (built in 1982) and it has a wood burning fireplace. We love having a wood burning fireplace, but we've recently noticed the hearth gets very cold and there's quite a draft coming from the fireplace. We've read and been told to close the flu and hold a tissue in the fireplace to see if it moves (indicating a draft through the flu). We've done that and the tissue does not move. We've used fireplace caulking around the fireplace between it and the brick surround.
The draft seems to be coming from the vents underneath the fireplace (sorry, not sure what that's called). It's as if the area around the fireplace itself is letting a draft in. We want to continue using the fireplace and hate to block these vents, but we've covered them with towels for now while it's not being used. Is there a way to remove this vent covering and insulate underneath there or is there something we should do at the top of the chimney that will solve this?
Replacing the insert is a bit costly for us right now. Is there anything else we can do to cut down the draft from under the fireplace?
Thanks in advance for your help!
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shederr wrote:

I'm having a hard time figuring out what you might mean by "vents underneath the fireplace". Three possibilities I can see are 1) an ash pit 2) air vents from outside which provide makeup air to the fire and 3) some sort of heat circulation arrangement but these probably aren't all the possibilities.
What sort of firebox does your fireplace have (steel, masonry?). Where are these vents located relative to where the logs rest on the grate or andirons? Are there other vents than the ones you mention (like above the firebox opening)? Is this fireplace a pre-fabricated unit that was inserted into an opening in the wall with bricks added for decoration?
--
John McGaw
[Knoxville, TN, USA]
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The firebox is steel. I don't have a picture, but found a couple through MSN images that are close to mine. The urls are:
http://www.royalhomes.com/options/img/large/Woodburning-Fireplace.jpg
and
http://www.fireplacesnow.com/gif%20files/11bgd48n.jpg
Hopefully you can get to these url's.
Anyway, the vents that seem to be drafty are below the box area where you place the logs. There are also vents just inside the doors on both sides. They each have a chain coming through them with a pull that says "pull to close". I'm not sure what those are supposed to be closing. There are also vents at the top above the box but there is no draft from there.
The unit is not set into (flush with) the wall, it sticks out from the wall.
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shederr wrote:

If the doors are airtight, or nearly so, then the side vents inside the doors may be for makeup air for combustion. It seems a good chance that the vents above and below the firebox are connected and are for extracting heat from the metal enclosure (in at the bottom and out at the top when the metal enclosure is hot) to heat the room. I'd certainly close the side vents when there is no fire, just in case they are part of the problem.
You can probably get closer to figuring out what paths the draft is taking if you can obtain a "smoke pen". This item can probably be found at a well-equipped hardware store although I haven't actually looked for one myself. It might just be that the firebox is cold enough that air is naturally entering the upper vents, going behind the firebox, and then falling out the bottom vents. Of course it could also be that there is a humongous hole back there somewhere leading to the outdoors. Does anything show outside the house near the fireplace -- like a screened air intake?
--
John McGaw
[Knoxville, TN, USA]
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John, I'll take a look at it tonight and see if there is a screened air intake outside the house. What if there is?
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shederr wrote:

what you might need is this http://www.woodlanddirect.com/Chimney/Top-Sealing-Chimney-Dampers/Lyemance-OPC-Chimney-Cap-Damper I bought and installed it when my throat damper burned out, it is easy to install and works great, for the metal firebox just use self taping screws to mount the handle inside. If you google Chimney Cap Damper you will have alot of good info at your finger tips!
Clark...
--
Don\'t you have Google in your part of the world?



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We have a similar fireplace (Heatilator, not sure what model) in our house, and a similar problem. I think in our case about 20% of the cold air was coming down the chimney (even with the damper closed) and 80% was coming thru the vent at the bottom.
The fireplace is mounted on an outside wall, in an enclosed wooden space that's not insulated. I suspect the design of the fireplace is intentionally "leaky", to allow outside air in for combustion and to circulate to keep the firebox cool. Since the space the fireplace is installed in is also apparently leaky, this provides a path for cold outside air to enter the room.
The only solution I could think of is pretty lame but it works. Our fireplace has a mantel (not sure if I'm using the right term here) that not only goes across the top but also down the sides. I cut a large piece of plywood to fit inside the space formed by the mantel and the hearth, and put foam weatherstripping around all the sides so it seals. Attached a couple of handles so it can be easily removed to use the fireplace and replaced afterward.
Like I said, it's not the prettiest thing in the world and I have to be VERY careful not to put the cover in place if there's even one ember glowing in the fireplace. But it does work well, the room is a lot warmer now.
Our planned long-term solution is to lose the cheesy fireplace and put in a woodstove instead. ;^)
Eric Law

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