Cold Drafty Fireplace -- Solutions?

[[email protected]]

Hi- I have a problem with my fireplace that I am not sure how to solve. I moved into a house with a Lennox wood burning fireplace in the den room. The model is "LBR 4324". From what I can tell, it is a "zero clearance fireplace" that vents out through a metal exhaust (called a B-Vent??) through the roof above it.

My issue is this: when the temperature gets very cold outside, the entire fireplace box gets VERY cold, and it makes the entire Den room cold and uncomfortable. There is also a very clear air gust flowing throughout the fireplace and into the room

At first I thought the obvious solution is that the cold air is coming down the metal chimney into the fireplace, but I fully sealed the damper shut, and the cold air was still coming in at the same rate that it was before, so the source of the cold air is NOT through the damper of the chimney. BUT WHERE ELSE COULD IT BE COMING FROM? I can only think of three other sources:

1. I have read online about fireplace having a combustion air intake vent attached to the side. Could this be the source of the cold air? If so, how can I stop it?

2. Is the fireplace possibly open to the back or the side or the bottom, so that cold air can get into the box from any of these sides?

3. Could it be that the cold metal chimney vent is making the firebox cold by touching it (i.e. by conduction)? I find this hard to be believe, because the entire firebox is freezing on cold winter days.

If you have any suggestions for what is causing this, I would greatly appreciate your help, as this condition is making my living room unbearable in the winter time!

Thanks,

Oliver

 

[bluedogz]

Five will get you ten that the info you'll get here will focus on your chimney height.

The damper is not intended to be airtight, so it very well could be the source of your draft, especially if your house is very tight. My masonry fireplace does the same thing.

Could it be that the cold metal chimney vent is making the firebox cold by touching it (i.e. by conduction)?

Doubt it.. but could be by CONVECTION.

 

[greythorn3]

ya my fireplace gets cold comming from under the mantel, so we put pillows under there in winter, and carboard behind the glass inside it, helps some. try that.

 

[mellow]

Does it have an outside air kit installed? That is where I would focus on.

 

[[email protected]]

how can I tell if there is an outside air kit installed? are there any obvious signs to look for? There is nothing on the inside of the fireplace that clearly shows this, as far as I can see.

 

[mellow]

http://www.lennoxhearthproducts.com/resources/brochure/Lennox_Hearth_LBR_Brochure_785305M.pdf

From what I can see it looks like it has an air port on the left side facing the fireplace, look to see if you have a vent on the outside that would look like a drier vent.

 

[madison]

Are their gas logs in this unit or are you burning wood?

Outside on the chimney chase you will probably find something that looks like a cloths dryer exhaust trim piece covering the vent. You may be able to plug it, if you do not intend to use the fireplace. More than likely the gas logs in the fireplace would function normally without this vent as long as the fireplace doors are open, close the doors and depending on how tight the doors seal it may or may not function properly.

I would also check with your local building inspector to find out if the vent must remain open and not plugged, it could be a code issue with the gas logs.

Or, stick around the forum, learn, and consider ripping the prefab out and put in a real heat source.