outside air

[bobnoffs]

my harmon stove uses outside air . anyone have any idea how many btu's are given up to heat outside air vs. taking inside air for combustion?
bob noffs

 

[bholler]

my harmon stove uses outside air . anyone have any idea how many btu's are given up to heat outside air vs. taking inside air for combustion?
bob noffs

It is more efficient to use outside air than inside air

 

[gthomas785]

I've wondered about this. For sure, using outside air increases comfort by reducing the count of cold air being drawn into the house. But the colder air from the OAK must affect the fire and heat output somehow, no? Perhaps it's negligible.

 

[Das Jugghead]

I've wondered about this. For sure, using outside air increases comfort by reducing the count of cold air being drawn into the house. But the colder air from the OAK must affect the fire and heat output somehow, no? Perhaps it's negligible.

I am with @bholler in that using outdoor combustion air is far more efficient than using indoor air. The effect of cold air into the firebox is indeed negligible.

I went from using indoor air to using outdoor air and it made an enormous difference in the comfort level in our home. Additionally I designed an intake that preheats the incoming combustion air which does help the stove light off the secondary burn much sooner than it did last year. Now I just have to slow down the burn to reduce the frequency of reloads - I have plans to rework the flue to accommodate a key damper in the spring. With a small firebox (a little over a cubic foot) and being a low-end stove I am always looking for ways to squeak out every little bit of efficiency that I can.

 

[bobnoffs]

after looking at the mechanical set up of the intake it seems that the stove takes outside air that is being warmed, at least some, by the exhaust chimney. that right there would be more energy efficient than sucking truly outside temp. air from every airleak in the house.
bob noffs

 

[jetsam]

I've wondered about this. For sure, using outside air increases comfort by reducing the count of cold air being drawn into the house. But the colder air from the OAK must affect the fire and heat output somehow, no? Perhaps it's negligible.

It's probably negligible, and even if it's not, the amount of already-heated air drawn out of the house by a wood stove is huge (think ~30cfm for an EPA stove, maybe ~500cfm for an open fireplace). Every cubic foot is replaced by dry, ice cold air from the outside.

Even if the stove suffered a large performance hit (which it doesn't), it would be more efficient to use outside air.

This is also why it's so cozy to sit by an open fireplace- because every other part of your house is gonna be freaking cold when that thing is burning!