Vent Above and Below Fireplace
Having moved into a new home in the summer, we were surprised in the winter when our living room floor was cold to play on with our baby. There was a distinct draft coming from the fireplace. Had the flue been left open? No, it was the vent intake below the fireplace. A fan sucked in air below the fireplace and blew warmed air out above it, just below the mantle, presumably to make the fireplace more efficient.
I took the vent grill off below to look underneath, and, of course, there's nothing under there in terms of insulation. So how does one prevent cold winter air from guttering from this area? What was left off in contruction to cause this, or what has failed? I have no idea how to solve this or even who to call the fix something like this.
Can anyone tell from the description in the above post whether I have an insulation problem, a vent problem, or just shoddy workmanship?
Thanks for your reply.
Not enough information. Gas or Wood, inside or outside chase. A pic would be good also.
It sounds like you can cold air infiltration from a gas direct vent fireplace or possibly a wood burner with gas logs. Regardless, cold air comes in because of pressures. Where it comes in is due to opportunities otherwise known as the Path of Least Resistance. Open a basement or other opening low in the house and your cold air should stop infiltrating there.
Seal the upper level penetrations and bypasses first. Next, provide fresh makeup air down low. Third, consider a Level III inspection of the chase. While open, you can have the specialist weatherize the chase but that will be costly. It does allow the opportunity to inspect for proper clearances and installation.
Keep the fire inside the fireplace.
Sounds like an old Heatilator Wood Fireplace
I've heard this problem described many times in our area. It can happen on wood or gas ZC boxes in uninsulated chase situations. In this case it sounds like an old heatilator wood burning fireplace.
They were the latest and greatest thing 30 years ago for masonry fireplace options. They feature a wood fireplace made of metal with air circulation around the box. The air would come from the bottom or sides of the hearth area in the room and heated air would discharge directly above the fireplace opening or off to the sides. When the fireplace was burning they could take a standard 5% efficient masonry fireplace and turn it into something that was 3 times better - or 15% efficient.
However, when it was not in use and cold temperatures could cool the metal box (from the flue or even just infiltrating through the chase / chimney structure itself) - it would turn the fire box into a more efficient cooling device. Often, even when the damper is fully closed, you can feel air moving around the box - usually in reverse with cold air coming out of the bottom grills.
To fix this, I've seen people cover the intake grates especially at the bottom, and sometimes even stuff them with insulation. I recommend that they be uncovered when you do go to use the fireplace so you can get the maximum benefit from your fireplace. (In the case of other ZC boxes there might be some other things I would do instead...)
Hope this is helpful. If this is not your type of fireplace that I have described, please submit a clarifying description and I can adjust my recommendations.
This sounds like the problem I am having (or WAS having when it was colder). I guess I need to figure out how to temporarily insulate the area around the fireplace when its not in use without it being impractical for removal when I want to have a fire. Even if I wasn't concerned about maximum efficiency, I would worry that the insulation would burn or melt.
Thanks for the description!
fix the problem
Fix the root cause instead of treating symptoms.
FYI, if you operate the fireplace with those louvers blocked, you could burn the house down.
Just thought you might like to know....
Keep the fire inside the fireplace.
I agree hearthman...
Yes, fixing the root problem is what needs to occur. That is why I agreed with the other posts that more information needs to be obtained before attempting the ultimate fix. As I noted, the fix will ultimately depend on the kind of fireplace it is.
If it is the old masonry heatilator fireplace I described with vents seperate from, but circulating around the fireplace itself - then the fix I described goes to the root of the problem and will not cause a house fire since this box is not a ZC box and is installed in a masonry chase with clay flue tile flue. The circulation is not needed to keep the box cool and is there only to increase heat output.
If it is a ZC box then what you say is absolutely correct and the source of the cold air needs to be found and addressed. Causes could be numerous and range from actual air leaks to an uninsulated chase - and everything in between.
On a ZC (zero clearance) box - even an old one - there should be some kind of manufacturer's tag or marking. Sometimes those get lost or removed over time, but that is the first thing to look for. Another clue to see if it is a ZC box is to look at the flue. Is it masonry or metal? If you still can't tell, it is high time to get a professional to look at it before you start making changes and get in over your head.
Sounds like Westerlee has a descision to make...
Westerlee, probubly the biggest questions here is... do you want to use the fireplace or not.
If you dont want to use the fireplace and you just want to stop the draft then you (as a homeowner) can do about whatever you want to insulate and air seal it within reason. Just make sure to mark the firebox real well that it is disabled so you dont have an unwitting house guest that starts your home on fire by using the disabled fireplace.
If you do want to use the fireplace, your hands are going to be severly tied as to how you can correct any of the heatelator issues you have here. If there is more than 4 inches between the tubes running through the fireplace you can maybe put in a chimney balloon fireplace damper to stop the air comming in through the flue area but that may be about it.