Outdoor air supply in wood stove insert

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mainemac

Member
Mar 10, 2008
139
Maine
At the risk of a major back and forth battle akin to "cover your wood" vs "leave it open" and "CAT" vs "non CAT"

I would like to ask about OAK

I was talking to a friend about his Hearthstone Equinox.
He heats creaky old house with 4 cords a winter but was excited to tell me about his outdoor air tube.
He is very handy and rigged this himself.
He hooked up the back of the equinox to a tube that connects to outside. He noted immediate improvement.
Claims as soon as he hooked it up there was less draft in his house, and the heat cranked out then
dissipated into 2 adjacent rooms in 10-20 minutes that had previously not had heat previously.
Since the fire had plenty of OUTSIDE air fueling the flames, there was less need for the stove to Pull air through
all his creaks and cracks in the doors windows, etc.

I of course was interested in this. Do others have same immediate improvement?
Is it only for free standing stoves? Not sure my insert would be able to have the same set up or not?
I like many others have a creaky drafty old house that I tinker with caulking insulating and storm doors all the time.
Central chimney with SS liner to the top. 2400 Sq house
Thanks

Tom
 
In my experience, only some people notice a difference with one. If you have an abnormally tight house it might be useful. A good way to test if your house will benefit from one is to open a nearby window. If there is a noticeable difference in the way the stove burns an OAK might be a good investment.

Keep in mind that they can introduce other problems into the equation depending on the particulars of your house and location. If the OAK is on the windward side of the house, you may get a bit of a turbocharge effect on the fire during strong winds. They also need to be clear of snow.
 
Using outside air for combustion does have several positive advantages. You're not using already heated interior air to burn the wood, you're not creating negative pressure inside the house which draws cooler air in through doors and windows to replace the air that's gone up the chimney, and it gives the stove plenty of combustion air if you have a very tight house. The problem would be how to adapt it to an insert. Stoves that are designed to use an outside air source have a place to attach a duct. Your insert doesn't and if it can't make a good seal and deliver the air directly to the stove air intake it isn't going to work properly.
 
Wood Heat Stoves said:
Stoves that are designed to use an outside air source have a place to attach a duct. Your insert doesn't and if it can't make a good seal and deliver the air directly to the stove air intake it isn't going to work properly.

Not really true, you could still install a fresh-air intake, and have it end close to the stove's air intake.
This is called a "passive" outdoor air supply.
Some wood stoves come without an outside air provision, the their manuals recommend having a fresh air duct ending near the stove, if needed.

Some VERY good reading on Passive air supply vs. Direct to combustion chamber air supply can be found here:
http://www.woodheat.org/the-outdoor-air-myth-exposed.html
 
This is interesting. An OAK appears to have advantages and disadvantages, dependant on the installation.

When we built, I decided against an OAK for the WinterWarm (which is factory fitted with an OAK adapter) mostly due to cost and complexity, not performance. Now I would have to hamer through 12" of concrete pad to install one, so it's out of the question.

Our house is pretty tight, but I'd say the WinterWarm at operating temp and throttled baclk, uses far less house air than a bathroom fan. Thr primary inlet is not much more than 2 square inches. Additionally, the secondary inlet cannot be hooked to an OAK at all -- always uses house air -- and it is about 3 to 4 square inches.

The mention of snow clearance is something I had not thought of either, and it would have been an issue all winter long, as the outside inlet has to be lower than the stove. It would have been right above grade.
 
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