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Thread: Outside air intake on wood stove?

  1. #1
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    Default Outside air intake on wood stove?

    Hi-I'm considering putting a outside air intake on my wood stove. I've heard this will make the house feel warmer due to cold air not being sucked in around windows, doors, etc. I understand the theory but am wondering about the reality of it. So anyone put one in and really made a noticable difference? I've read that the outside air kit will actually pressurize the house forcing warm air out instead of sucking cold air in.

    Thanks,

    KK

  2. #2
    Member walk-in's Avatar
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    I don't know about pressurizing the house just by adding an outside air intake, but probably the most immediate impact you will notice is that the stove will be easier to light and draft better. This is particularly true if you have a forced air furnace are clothes dryer running when you try to light the stove. Also, if your chimney is a wall exit, you will definitely notice the better draft...especially on warmer days in the fall or spring.

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    I have one installed in my place. You will notice a decrease in cold air coming in through the doors/windows. I had a noticeable difference in the amount of wood I was using to heat my place during the winters. The ideal gas law supports what you heard. If you keep the the volume constant and increase temperature, the pressure will rise.

  4. #4
    Member byrd_hntr's Avatar
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    Default More humidity

    Ive noticed that since Ive installed my fresh air intake the humidity doesn't drop inside the house so much. Before the intake I had a hard time keeping it running about 25% in my house, since the installation of the intake I run 38-40% which helps with the sinuses.

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    Default Atmosphere control

    Quote Originally Posted by byrd_hntr View Post
    Ive noticed that since Ive installed my fresh air intake the humidity doesn't drop inside the house so much. Before the intake I had a hard time keeping it running about 25% in my house, since the installation of the intake I run 38-40% which helps with the sinuses.

    That's a very good point, because you are using up the inside air for combustion, you can better control the water content inside. The air is awfully dry when the temp dips below zero.

  6. #6
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    Default Increase in Pressure idea rediculous

    Ignore the point about taking outside air for combustion directly to your stove somehow increases pressure in your house. This is hogwash, and someone was likely confused.

    Basic laws of Physics determine why air moves in and out of a structure. One basic idea to keep in mind is that all things want to be in balance-- to reach a point of equilibrium. Warm air moves to cold air untill they are the same temperature; high pressure moves to low pressure untill they are in balance. Woodstoves and most all other combustible appliances in your house use air from the house to combust the fuel and this air leaves the bldg up thru the chimney, exhaust fans, etc.. This air must be replaced somehow to reach the point of pressure balance, so it leaks back in where ever it can. It is always better to control where the air comes in than letting it decide on its own.
    Thus- the direct connection to the woodstove or appliance, when provided to do so, is always the best.

    It is all-to-common up here to have houses in some various state of pressure imbalance, and there are various factors at work here. Why this happens, and the causes, would be a topic all to itself, and far too detailed to go into here.

    Suffice it to say it is always a better system when we can "direct-vent" combustible appliances and "isolate" them from the building stucture--- by that we mean it balances itself by taking its combustion air and expelling the byproducts of combustion in a balanced exchange , and doesn't require air from the house to accomplish this.

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    Default Physics???

    Quote Originally Posted by Mr Bill View Post
    Ignore the point about taking outside air for combustion directly to your stove somehow increases pressure in your house. This is hogwash, and someone was likely confused.

    Basic laws of Physics determine why air moves in and out of a structure. One basic idea to keep in mind is that all things want to be in balance-- to reach a point of equilibrium. Warm air moves to cold air untill they are the same temperature; high pressure moves to low pressure untill they are in balance. Woodstoves and most all other combustible appliances in your house use air from the house to combust the fuel and this air leaves the bldg up thru the chimney, exhaust fans, etc.. This air must be replaced somehow to reach the point of pressure balance, so it leaks back in where ever it can. It is always better to control where the air comes in than letting it decide on its own.
    Thus- the direct connection to the woodstove or appliance, when provided to do so, is always the best.

    It is all-to-common up here to have houses in some various state of pressure imbalance, and there are various factors at work here. Why this happens, and the causes, would be a topic all to itself, and far too detailed to go into here.

    Suffice it to say it is always a better system when we can "direct-vent" combustible appliances and "isolate" them from the building stucture--- by that we mean it balances itself by taking its combustion air and expelling the byproducts of combustion in a balanced exchange , and doesn't require air from the house to accomplish this.

    Mr. Bill,
    Although I agree with most of what you posted, I find it difficult to understand several statements. e.g. "Basic laws of Physics determine why air moves in and out of a structure. One basic idea to keep in mind is that all things want to be in balance-- to reach a point of equilibrium. Warm air moves to cold air untill they are the same temperature." Can you help elaborate on this theory? It is my undstanding that hot air rises due to decrease in density as a result of expansion in volume from heat. Due to movement of air, convection currents are generated and air moves around in a confined space (that's why fiberlgass insulation was invented).

    On a separate note. I hardly consider the ideal gas law hogwash. For example, if you take a can of gas and heat it up, do you think it will increase in pressure? Of course this assumes the volume is constant and no leaks. I agree, that you would not feel this pressure increase.

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    Member ret25yo's Avatar
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    personal experience......... I have a outside air wood stove in upstairs in the living room and a inside air wood fireplace downstairs...

    downstairs is so so so so so so much easier to light. gets hotter quicker and in general would seriously consider one for my own house when I buy one.

    upstairs is just a pain to light gets cold really quick and burns wood quickly and finally it takes forever to warm up..

    If you cant stand behind the troops in Iraq.. Feel free to stand in front of them.

  9. #9

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    Any combustion is going to need oxygen to sustain itself. If you don't have an air inlet going directly to your stove then it's either going to pull air in from the outside or it'll burn poorly (lots of thick smoke, weak flame)/go out. I'm not sure what your exact setup is, but you can also just put a small vent near the stove for incoming air. Directly feeding the fire is going to be more comfortable for the buildings inhabitants.

  10. #10
    Member Matt S's Avatar
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    We have outside air on our stove, it works great. If your stove supports the setup I would do it.

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    Default Outside air

    There are good and bad points on having outside air tied to your wood stove or fireplace.
    When you have it set up it will help equal the pressure in the heated home by not causing a vac in the house.

    The neg point of drawing outside air is you are pulling cold air throe the hot stove. The problem with that is hot steel when hit with cold air tends to cause the welds to crack inside the stove.

    I saw this for many years when i was a chimney sweep in CO and i had my head stuck in thousands of stove.

    The UBC used to require outside air on furnaces as well and it would cause the heat exchanger to crack within a couple years.

    There is a lot of devices in the home that cause neg pressure i.e. draft hoods over the stove, bath room fans, wood stoves and furnaces etc.

    Some states or counties still require outside air on some appliances with in the home or modular.

    Just my 2 cents i hope this helps some.
    Regards T

    Sweepint
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    Member dkwarthog's Avatar
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    Anyone have an opinion on whether taking your woodstove combustion air from a basement would cause other problems?

    One potential problem I see is having flame problems on water heater and clothes dryer due to negative pressure in the basement.

    How about running the woodstove intake thru the basement then outside in a long duct so the air can pre warm a little before it gets to the stove? ...possible frosting/mold problems??

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    Default re:dkwarthog

    I think its a good idea but i do believe there may be some problems as a result of it.
    I think it would be harder to start the fire in the stove. The flue gas or chimney will only exhaust as fast as the make -up air enters the stove.
    The longer the run the more restriction of flow. For both ends.

    But on the other hand if it was a short run it would probably not afect the stove at all and you are back to the first issure again.

    I have never heard of anyone pulling combustion air from a basement to the above floor, but that does not mean it does not happen , i just have not seen it.

    We were able to pull a combustion air from the crawl space on mobile home in CO then the county came back a few years later and said they wanted it to the skirt of the trailer.
    Regards T

    Sweepint
    Wasilla, (when not overseas)
    '' Livn' The Dream ''
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