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?

johnl

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.

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...

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

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.

thanks-
johnl

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.

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!

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.
john

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.

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.

Best,

Mike

Just to clarify, you want a free standing fireplace or a woodstove?
I ask because many people use the term "fireplace" to describe a woodstove.
I use a woodstove and I bought a "fresh air intake" for it. I have yet to install the FAI because of having to put a hole in the wall.


Wow, I did not notice this is a really old thread.

Hole in the Wall gang
 

This IS a really old thread. However, it still rings true. If you are burning air inside the house it must come from outside somehow. Stove, fireplace, cooktop range, hot water heater, etc. My point was that when you have a 30-50,000 BTU burner (or logs) it requires a lot of combustion air that eventually comes from the outside. Without a specific directed source of this air it filters in anywhere it can leaving those areas where it filters in colder. Having a specific external combustion air path minimizes this effect. I assume that you are on a slab or cannot cosmetically duct air nicely without a hole in the wall. Well, good luck with your project.

Mike

A duct that brings outside air directly to the fire is the ideal.

We heat a 900 foot home in southcentral AK 90% with wood and a propane backup. We use about 2-3 cords per winter.

anyway we have a hole cut in the wall behind the stove. through the hole is a flange on the flange is a 3 inch dia. tube. from the small tube sticking from the inside of the wall is some 3 inch flexible aluminum hose into the intake at the back of the stove.

No backfire protection (I have never seen on with backfire protection)

I often see similar set ups sold as fresh air kits for pellet stoves.

A lady i know had a free standing wood stove installed , the installers put in a vent somewhat behind and to the side of the stove, with a flap on it smaller but similar to a dryer vent flap.