Adding an air supply to a open fireplace

[SudsJeff]

Hello all,
On the main level of our house we have a fairly large older "Heatilator" style fireplace with a 10x10 clay tile liner. I know these things don't tend to produce much heat, but we love the look of the open fire and primarily use our basement woodstove or propane furnace for heat. Over the holidays we were making a lot of fires in this fireplace for ambiance (the guests love it!) and we began to notice some pretty powerful cold drafts coming in the house (particularly at the stove hood vent). I should mention it was averaging around -18F. In the end we had to stop making fires in it since it was freezing the house.

As mentioned, I'm not trying to be BTU positive with this thing but just trying to have an open fire for ambiance. My question is, can a cold air supply be added to the firebox on this fireplace, and would it help?
thanks!

 

[begreen]

It could be possible, depending on the fireplace location. This might help a little, but an open fireplace is still going to suck out a lot of room air, even long after the fire has died down. An insert would be a better solution.

 

[SudsJeff]

[QUOTE="An insert would be a better solution.[/QUOTE]
I know what you're saying, but we really like the giant open fire (this thing is almost medieval!). The fireplace is on an exterior wall. We normally crack a window close by the fireplace, but our visitors were sitting near that window so we didn't want to freeze them with that draft.
Could I drill a hole in the bottom of the fireplace near the front where I never make fires and plumb in a cold air intake?

 

[begreen]

I know what you're saying, but we really like the giant open fire (this thing is almost medieval!). The fireplace is on an exterior wall. We normally crack a window close by the fireplace, but our visitors were sitting near that window so we didn't want to freeze them with that draft.
Could I drill a hole in the bottom of the fireplace near the front where I never make fires and plumb in a cold air intake?

It's been done before, but I doubt it's effective. The hole would have to be larger than for a small pipe. And there is the issue of safe installation. An open fireplace moves a lot of air up the chimney. Maybe look for an insert that has a screen option for open door burning?

 

[SudsJeff]

fair enough. So it is what it is until we have the $ for a fireplace reno.

 

[jatoxico]

Need picture of medieval fireplace.

 

[SudsJeff]

 

[moresnow]

Shame it isn't working. I grew up in a home with 2 fireplace's. Something about watching, listening, smelling them. Made me feel like I was camping I suppose!

 

[Simonkenton]

I have a fireplace, pictured at left. Yes the fireplace sucks in an enormous amount of fresh, cold air. Yes you can install an outside air intake.
Here is what I did. One of my crawl space vents is a concrete block turned sideways, two holes that are 5 inch by 5 inch, side by side.
I made a hole in the floor on the side of the fireplace, this hole is 14 inch by 6 inch. I installed a floor vent from Lowes in that hole.
Then I got a piece of flexible pipe, 14 inch diameter, black stuff that is insulated, and fastened it to the hole in the concrete block wall, and fastened it to the bottom of the vent.

Works great. When not in use I put a little rug on top of the floor vent.

 

[cjgoode]

My son's fireplace has a fresh air intake in the back. I figured it was something to push the ashes out of. But there is a grate in it so animal cannot get in, and you have to go outside to the back the chimney to open and close it to lot more air in or shut it off.

 

[maple1]

We have a Heatilator. Gets used VERY infrequently. It has a fresh air intake port on it, bottom left. With a 4" pipe to the outdoors. Has a door to open if you have a fire, & keep closed the rest of the time. Along with the flue damper & glass doors.

Strictly an ambiance appliance, contributes very little if any heat to the house.

 

[SudsJeff]

I have a fireplace, pictured at left. Yes the fireplace sucks in an enormous amount of fresh, cold air. Yes you can install an outside air intake.
Here is what I did. One of my crawl space vents is a concrete block turned sideways, two holes that are 5 inch by 5 inch, side by side.
I made a hole in the floor on the side of the fireplace, this hole is 14 inch by 6 inch. I installed a floor vent from Lowes in that hole.
Then I got a piece of flexible pipe, 14 inch diameter, black stuff that is insulated, and fastened it to the hole in the concrete block wall, and fastened it to the bottom of the vent.

Works great. When not in use I put a little rug on top of the floor vent.

That`s a beautiful fireplace. Its interesting because I also have a 4 inch pipe in the crawl space through one of my concrete blocks close to this fireplace. It is currently plugged with a large soup can (by the previous owners)...

I was thinking I could run some insulated pipe from this, through the crawl space, break apart the cement on the floor of the fireplace (close to the front left, see my last picture), and setup a vent as you did. Would you be able to provide a picture of your fireplace vent setup? Thanks!

 

[Simonkenton]

This is the floor vent.


This is the air intake in the block wall. As I said it is a block laid sideways, but, I forgot that I had knocked out the center section, to give more air flow. So the hole is about 5 inches by 12 inches.
Sixty square inches. You have a 4 inch diameter pipe, using pi R squared, we see that the area of your hypothetical vent would be 12, 13 square inches.

This is not gonna get the job done, too small.

What are the dimensions of your fireplace opening? The amount of air the thing will suck in is directly related to the size of the opening.
Mine is 42 inches by 36, 1200, 1300 sq. inches.

My fireplace is a very good heater. It is all masonry. The fireplace is entirely inside the house, so that, the back wall of the fireplace is the inside wall of the bathroom.
If you burn the fireplace for 5 hours, it will heat up that rock bathroom wall. Gets up to about 105.
That isn't very hot, but when you have 5 tons of masonry that is 105 it will crank out significant heat for 24 hours or more.
Also the firebox area of mine is built along the Rumford style and while burning throws an enormous amount of heat into the room.
Still, my fireplace uses five times as much wood as my wood stove.

You might get some decent heat out of your fireplace but you are going to need an outside air intake about the size of mine. How about a vent in the wood floor right in front of the fireplace?

 

[yooper08]

What about a chimney top damper? Closing it when not burning would seal off the chimney and house from those down drafts.

 

[Doc C]

I have a fireplace, pictured at left. Yes the fireplace sucks in an enormous amount of fresh, cold air. Yes you can install an outside air intake.
Here is what I did. One of my crawl space vents is a concrete block turned sideways, two holes that are 5 inch by 5 inch, side by side.
I made a hole in the floor on the side of the fireplace, this hole is 14 inch by 6 inch. I installed a floor vent from Lowes in that hole.
Then I got a piece of flexible pipe, 14 inch diameter, black stuff that is insulated, and fastened it to the hole in the concrete block wall, and fastened it to the bottom of the vent.

Works great. When not in use I put a little rug on top of the floor vent.

There also is flat magnets at most home improvement stores that are designed to go over the vents when not in use that cover pretty good.

 

[SudsJeff]

What about a chimney top damper? Closing it when not burning would seal off the chimney and house from those down drafts.

Im actually lucky with this one and I dont get any downdrafts through the flue while not in use (basement stove is a different story). The downdrafts and otherwise occur through bathroom and oven vents when I have a decent fire burning.

As an aside, I did purchase one of those fancy lyemance top-sealing dampers. What I found is that the flange and parts of the damper ended up slightly blocking the flow and I had to be very diligent about keeping a low smoke fire or it would vent into the living room. I ended up ruining a dinner party once and that was the end of that puppy, back to a standard chimney cap.

 

[yooper08]

Ah, I get the issue now. I reread your original post and I should've caught on to that.

 

[yinpin]

My son's fireplace has a fresh air intake in the back. I figured it was something to push the ashes out of. But there is a grate in it so animal cannot get in, and you have to go outside to the back the chimney to open and close it to lot more air in or shut it off.

Interesting, my upstairs fireplace has a metal door on the back of the chimney as well as a small access cover with a horizontal slot in it on the floor of the firebox. I assumed that this was strictly an ash clean out. If this was opened during a fire, wouldnt it act as a air intake? Is it an air intake? The basement fireplace does not have this.

 

[SudsJeff]

I If this was opened during a fire, wouldnt it act as a air intake? Is it an air intake? The basement fireplace does not have this.

When you make a fire do you feel cold air rushing in through that opening?

 

[bholler]

Unless you go with something really large like simonkenton did it is a waste of time and effort. It just wont supply enough air. And even if you are able to supply all of the air needed it is still going to be incredibly innefficent. You may get decent heat but you are going to go through massive ammounts of wood to get it.

 

[SudsJeff]

Unless you go with something really large like simonkenton did it is a waste of time and effort. It just wont supply enough air. And even if you are able to supply all of the air needed it is still going to be incredibly innefficent. You may get decent heat but you are going to go through massive ammounts of wood to get it.

Yes, I've been doing some reading on room makeup air and house depressurization. It will be challenging to get the 400-500 CFM of air to this baby, certainly not through a 4" round (even with a 200CFM inline blower motor and a short run. ). As mentioned in my original post, my concern is not generating heat with this fireplace, but is purely for ambiance. The issue is that the depressurization is so bad that you actually get a pretty powerful down draft through the kitchen and bathroom vents (luckily most of my appliances are direct vent or electric). As in you're sitting on the toilet and get a -20 wind blast on the top of your head.

One article I came across describes a scenario where using flow restriction, like glass doors, can reduce air requirements by 1/4. http://www.woodheat.org/fireplace-tight-house-32.html

The total cost to test this outside air supply will be about 100$.
.

 

[bholler]

Yes, I've been doing some reading on room makeup air and house depressurization. It will be challenging to get the 400-500 CFM of air to this baby, certainly not through a 4" round (even with a 200CFM inline blower motor and a short run. ). As mentioned in my original post, my concern is not generating heat with this fireplace, but is purely for ambiance. The issue is that the depressurization is so bad that you actually get a pretty powerful down draft through the kitchen and bathroom vents (luckily most of my appliances are direct vent or electric). As in you're sitting on the toilet and get a -20 wind blast on the top of your head.

One article I came across describes a scenario where using flow restriction, like glass doors, can reduce air requirements by 1/4. http://www.woodheat.org/fireplace-tight-house-32.html

The total cost to test this outside air supply will be about 100$.
.

Yes doors can reduce the air requirements. But in doing so you can end up with a creosote issue. Some fireplaces need tgat much air going through them to work properly.

 

[bholler]

Yes, I've been doing some reading on room makeup air and house depressurization. It will be challenging to get the 400-500 CFM of air to this baby, certainly not through a 4" round (even with a 200CFM inline blower motor and a short run. ). As mentioned in my original post, my concern is not generating heat with this fireplace, but is purely for ambiance. The issue is that the depressurization is so bad that you actually get a pretty powerful down draft through the kitchen and bathroom vents (luckily most of my appliances are direct vent or electric). As in you're sitting on the toilet and get a -20 wind blast on the top of your head.

One article I came across describes a scenario where using flow restriction, like glass doors, can reduce air requirements by 1/4. http://www.woodheat.org/fireplace-tight-house-32.html

The total cost to test this outside air supply will be about 100$.
.

Doors also may work well and have absolutly no negative effect at all. There are just to many variables involved to know without trying it.