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jlinstrom 08-18-09 06:08 PM

Fireplace and outside air
I want to put a free-standing fireplace in my cabin and am curious about using (cold) outside air for combustion. I know using (warm) house air is dumb, but net searches haven't pulled up much discussion...
Anyone done this? Heard of this? Anyone? Bueller?


Daox 08-19-09 02:07 PM

Thats a good question. I'm no expert on fireplaces, but I don't think you'll be able to use the fireplace as is. You would literally have to make an intake duct and hole for it. As long as it is placed lower in the fireplace itself, it should naturally pull air in as hot air exits from the top.

jlinstrom 08-19-09 02:22 PM

fireplace and outside air
yeah, I figured that.
But even if I did that - what about backfire protection, vent size, a cold air pump...?
I can't believe I'm the first bozo to ask this question and the firplace insets I've seen, those with double jackets/fans, all pull warm combustion air!

You can literally feel the draft of combustion air being pulled up the chimney in a fireplace. Old friend, former Marine gunny, comes into the house one fall, fire burning crisply, and announces: "fire for effect!" How true.

I'll continue my search and add to this thread as fact arise...

Daox 08-20-09 12:19 PM

I did some googling and found these links. They should help you figure things out.

Fresh-Air Intake Vents

Fireplace Design - How An Energy Efficient Fireplace Design Can Save You Big Money

This one is a bit less directly tied to your question, but seems like good info none the less.

How to Make Your Fireplace More Efficient

About fireplace inserts and hearthmounted stoves

jlinstrom 08-20-09 05:12 PM

fireplace & fresh air
I spoke too soon - I googled again and found a bunch also. This was from 6 months ago or so...
Big deal about drafts and 'tight house' and it all makes sense.


Ryland 08-21-09 10:23 AM

Most well designed fire places have a fresh air intake in the bottom, it is sometimes mistaken as an ash dump, even in a drafty house it can help to use this fresh air vent on over cast days, but the idea is to pull in air right to the fire instead of pulling air through the gaps in your doors and windows.
If a fire place is designed well and operated correctly it can heat a house, if it's poorly done and dampers are left open, wood is not dry enough, or any other short cuts are taken and you will suck more heat out of your house then the fire produces.

bennelson 10-14-09 11:28 PM

I completely agree that it seems hard to find some really good information on using outside air for either a woodstove or fireplace.

Look at any modern natural gas furnace - it will have two PVC pipes going straight to the wall - one for fresh air in, and one for exhaust gas out.

That's really what you want for your wood fire, except that the exhaust gas pipe should be vertical, metal or stone, and bigger diameter!

jlinstrom 10-15-09 09:33 AM

cold air feed
I'm tossed between a passive air input tube and forced air...
Fans and impellors are a hassle to size and run, but fire draft will draw air in from SOMEWHERE, best if from a desired source.
Everything I read about fireplaces says using heated house air for combustion decreases efficiency and limiting air limits combustion (some help) but cools the smoke and makes creosote buildup more likely. Wish there was more discussion on this in the marketplace - I think the idea is to sell 'pretty' and let the customer figure out the 'just open a window some' solution.

dremd 10-15-09 08:39 PM

Mine has a cold air feed!
Doesn't work because I don't have a front on it . . . . . .
Of course that's mostly irrelevant since I can use it MAYBE 10 nights a year; and have been known (in the past) to run the A/C so we could have a fire on Christmas day.

Mike.Steen 08-31-13 05:18 PM

Using outside combustion air for a fireplace
I have read a lot of low and high tech discussions on whether it is a good idea to use inside combustion air but nobody mentions the net effect of sucking in outside air on the other rooms in a house. Have you ever noticed that the room where the fireplace resides is nice and toasty while the other rooms are cold? Outside air is being sucked in from every corner and crack and vent to feed the fireplace. This is why I am still a fan of a separate outside combustion air source.



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