Fresh Air Intake for a Woodstove or Wood Heater W/ Round Intake

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Introduction: Fresh Air Intake for a Woodstove or Wood Heater W/ Round Intake

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Lots of people don't realize it, but when you use a heating appliance that is vented to the outside, every cubic foot of air that goes up and out the stack has to be replaced in the room. With the regular old fireplaces and pot belly stoves we know and love, that replacement air is going to be many, many cubic feet per minute and is going to be in the form of cold air seeping in through cracks, under doors, around windows... any way it can get in. Otherwise there would be a vacuum formed in the house, your ears would pop, the canary would die and eventually your house would implode.

Well, okay, I got a little carried away... actually, if your house is that tightly sealed, your wood burning device would burn slowly and it would be difficult to get a good draft going up the chimney. A lousy draft = a smoky wood burner or fireplace with a lot of the smoke ending up indoors.

My old house is nowhere close to being tightly sealed. When I had a good fire going in the wood burner, I could put the back of my hand up to the crack in the front door jamb and feel the cold air being pulled in. A lot of the work of the heater was going toward heating that cold air! I finally decided to do something about it. But what? The air intake on the front of my stove was a round design with a built-in adjustable damper and it swung open with the door when it was opened to add wood.

Step 1: Adapter

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After tossing around many, many ideas that eventually got dismissed because of complexity or cost or being a pain to remove every time I wanted to add wood, I thunk this one up. It went together so easily that I was kicking myself for not thinking of it sooner.

While replacing old rusty flue pipe, I noticed that a 6" 90 degree elbow perfectly fit over the round air intake on this stove. All it needed to secure it was a small angle bracket, pop rivited to the elbow and held to the stove door with sheet metal screws.

I had just bought some dryer vent hose for another purpose, and my quick-as-a-snail brain put the two together.


Yes, I've got rocks on my stove. They serve as a small thermal mass that slowly releases heat into the room after the fire has gone out. The smooth rock on top of the granite block is my bedtime foot warmer on really cold nights. Behind the chunk of granite is a pile of aluminum ingots from my backyard foundry. Sometimes the granite gets replaced by a big pot of lima beans or corn on the cob!

On top is a small amethyst "cathedral" that I put there just because I think it looks purdy.

Step 2: Mounted Adapter

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You could use more than one mounting bracket, but I found that the weight of the pipe and hose holds the elbow securely enough against the door.

Step 3: Air Control

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The only drawback of this scheme is that I can't reach the air intake damper to adjust it from outside. I'd have to open the door and adjust it from the inside. But I pretty much leave it wide open anyway and control the draft with the flue damper if I need to.



I think I need to invest in a bottle of stove-black.

Step 4: Uses the KISS Principle

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This is 6" flexible foil dryer vent hose that you can get at most any home improvement store. It is secured to the elbow with metallic heating & air duct tape. It looks so much like the foil of the hose that you can't tell where one ends and the other begins.


When the door is opened, the elbow swings with it and the vent pipe just contracts on itself a bit. Works great!



No, the vent hose is in no danger of being damaged by heat. Even with a hot fire going, the vent hose and the elbow both become cold to the touch because of the cold air flowing through it from outside the house.

Step 5: It's Not Pretty But It Works Really Well.

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I didn't even have to cut an opening to the outside. Back when I used central heat, there was a 4" x 10" heat register mounted in the floor right behind where my stove is located now.

I just bought a 4"x10" to 6" round adapter (also at the home improvement store) and adapted my vent hose to the register.

The heat duct under the house is disconnected, so fresh air is pulled in from under the house.

We are just finishing our first winter season of using the stove with this fresh air intake system and there have been no problems associated with it.

My housemate said she could tell the difference right away because it was easier to heat the house and she wasn't having to chop as much wood.

'Nuff said.

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    17 Comments

    "every cubic foot of air that goes up and out the stack has to be replaced in the room."
    Please correct me if I am wrong, but I do believe a lot of the exhaust is coming from the wood being converted to a gas. As an example, the average weight of air is 0.0807 lbs. per cubic foot. So a 10 pound log when burned will produce 123.92 cubic feet of exhaust gasses. More if you consider that hot air takes up more space than room temperature air. The wood doesn't just disappear. I think the amount of mass that is lost is almost immeasurable.

    I know this is a really old post, but you did say to correct you if you were wrong. Last time I checked, fire needs oxygen to continue to burn. Much of what is going up the chimney is exhaust from the wood itself but the fire needs to pull oxygen from somewhere. If you do not have an outside supply, it will pull it from inside the house which will depressurize the house and the fire will burn poorly.

    u didnt know this but if u put a small chunk of live ember into that amethyst. it would actually heat up an make light.

    I know this is hasn't been posted on in a while, but it will always be good information. Now that you are pulling more cold air into your crawl space, does the floor seem any colder? I was thinking that you could pipe from that floor register directly outside through the wall, and further reduce a little of the heat loss from your house.

    Our family has an old vacation property in upstate NY that was FREEZING cold during the winter that we stayed there, and it was because of the negative pressure and air leaks that you mentioned. I think that this would go a long way towards a remedy. Thanks!

    I have seen people put a coil of copper pipe on the stove, then run it over to a radiator with a pump and a fan on the radiator....warms 2 places at once

    Do you know how much heat you're losing out of the flue? I have a vague idea that it would be good to use the flue gas to pre-heat your air intake, via some kind of heat exchanger, but not much more than that. ? L

    I think my father's experience somewhat answers to your question (see my recent post).

    Have a good week

    "Do you know how much heat you're losing out of the flue?" Yes, a lot. I usually point a fan at the flue to rob some of the heat before it makes its exit. I have thought about putting fins on the flue. But I have friend that owns a tree service and he dumped a huge dump truck of oak and pecan on the back of my lot so the wood is practically free. Just a bit of labor to cut it up and split it.

    Thanks for the reply - I can see some of the flue, I know you can get a lot of heat out of them. Or on the case of one I know a shed full of smoke... L