Which stoves have outside air kits that are really tight?

[John Ackerly]

I hear that a lot of outside air kits bring outdoor air right into the stove, but the stove still uses some room air. Is that true? I'm curious because Alliance for Green Heat often gets questions from people building "green" homes, and some are trying to get passive house certification, which is a high bar in terms of ventilation. For a stove to only use outside air, I guess that means you can't leave the door open for the first 15 minutes and the outdoor air supply has to be big enough to get fire going. Can some do that? I have been one of the skeptics of outside air, based partially on arguments made by John Gulland on Woodheat.org. But with houses getting tighter and tighter, there is definitely a niche for outdoor air kits and stoves that are genuinely a closed system and can't draw any air from the room. Any insights, brand names, etc. appreciated. Thanks!

 

[kennyp2339]

Blaze King - all there stoves are controlled with a t-stat, all the air the stove needs comes through on inlet at the bottom rear of the stove, the outside air kit hooks directly to that.
You can keep the door open to get (extra air for the initial fire) you may want to make sure that you don't have a dryer or vent fan going though if your house is really tight.
I had an oak setup for my stove, (BK Princess) I liked it and did notice that it cut down some of the draft inside the house, unfortunately my stove is located in a below grade basement and the oak had to be raised approx. 6ft to daylight which is unsafe because if there's a reverse draft the oak could act like a chimney and bad things could happen.

 

[blades]

Most if not all take combustion air from inside, in addition to the out side air connection and will function just fine without that piping installed. I do not know if there is a model produced that "only" uses outside air for combustion - that would be A TRUE SEALED COMBUSTION UNIT( once the loading door is closed) Frankly I would likely be climbing all over it if it was available. Back in the 80s/90s some units were advertised as sealed combustion units, it was a marketing slight of hand as they still used air drawn from within the structure for combustion. ( I have one sitting in my garage, advertised as such, imagine my surprise when I had a run a way stove one day - closing both air controls fully had no effect as far as dampening the fire in the unit, and the 4.5ft long double walled pipe leading to the ceiling transition unit was dull red in short order. Scared the x out of me. This was in a mobile home at the time. That particular load of fuel was from the same stack as the day before4"x4"x6" cut offs of mixed hardwood. Never did figure out just what the heck made it go ballistic. So that was my education on "sealed" stoves and marketing hype)

 

[John Ackerly]

Most if not all take combustion air from inside, in addition to the out side air connection and will function just fine without that piping installed.)

Thanks Blades. This is what I've heard. Not sure if genuinely sealed systems are more common with pellet stoves. Hopefully, someone can vouch for a wood stove that really seals off the use of indoor air.

 

[begreen]

Some stoves take all air from a single inlet where the OAK connects like the Jotul F400-F600.. Others dump the air in the vicinity of the secondary and primary air inlets, but they are not directly connected, example: some PE stoves.

 

[CenterTree]

... For a stove to only use outside air, I guess that means you can't leave the door open for the first 15 minutes and the outdoor air supply has to be big enough to get fire going. Can some do that? I have been one of the skeptics of outside air, based partially on arguments made by John Gulland on Woodheat.org. But with houses getting tighter and tighter, there is definitely a niche for outdoor air kits and stoves that are genuinely a closed system and can't draw any air from the room. Any insights, brand names, etc. appreciated. Thanks!

Just an FYI:

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.

 

[bholler]

The argument against outside air on wood heat is greatly exaggerated. Yes if an intake is installed in the wrong spot or incorrectly it can cause problems. But in some cases they are needed. And in many more cases they can be beneficial.

 

[John Ackerly]

Just an FYI:

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.

Thanks for these links. I often end up at your site and find great info there. (What's with the black background though?).
Do you know any way of telling which stoves only take air from the OAK, and not the room? Woodstock Soapstone does that apparently in their Absolute Steel Hybrid, but surely there are others. Seems like there should also be a voluntary test that the EPA accredited labs can do that can prove to consumers that the stove can't take indoor air.

 

[BrotherBart]

Thanks for these links. I often end up at your site and find great info there. (What's with the black background though?).

It isn't CenterTree's site. It belongs to Tom Oyen. Forum member "thechimneysweep" .

 

[Highbeam]

Perhaps through luck, the last two house stoves I have bought got 100% of their combustion air from the OAK stub. The BK princess and the Hearthstone heritage. Each had a nipple on the rear that fed combustion air to the stove and no other holes.

The shop stove, an Englander NC30 has no less than 4 places that combustion air enters the stove and only one of those is used for the OAK. That is silly I think.

A totally different question is whether you can light any stove without cracking the door during initial warmup. I've never owned a stove that would start faster with the door closed if at all. So during that time, room air is feeding the fire.

 

[bholler]

A totally different question is whether you can light any stove without cracking the door during initial warmup. I've never owned a stove that would start faster with the door closed if at all. So during that time, room air is feeding the fire.

Neither of my stoves have ever needed the door cracked to light. But I have a 30' chimney. It is not the stove that determines if you need the door open to start it is the draft.

 

[Sprinter]

The argument against outside air on wood heat is greatly exaggerated. Yes if an intake is installed in the wrong spot or incorrectly it can cause problems. But in some cases they are needed. And in many more cases they can be beneficial.

Exactly. I've never seen a really good reason not to use outside air for combustion (maybe a basement install or something specific). In fact, in Washington State, it is mandatory for all new construction and in some areas, mandatory for any installation.

I never have to crack the door open to get the fire going. In fact, it usually starts better with the door closed because the airflow is better controlled, even with control full open .Of course that can depend on the fuel, how it's packed in, how it's started (I use SuperCedars), etc . My flue is only 13', but some stoves are more forgiving of short flues than others.

 

[Sprinter]

have been one of the skeptics of outside air, based partially on arguments made by John Gulland on Woodheat.org. But with houses getting tighter and tighter, there is definitely a niche for outdoor air kits and stoves that are genuinely a closed system and can't draw any air from the room.

The way I look at it is that the air will take the "path of least resistance". If outside air is available, especially in a tight house, that is what will be used, even if there may be a slight path available to the interior of the house. For example, my stove gets air from a bottom plenum. If the outside air is made available, that is what will be used. If not, it will take air from the house. The plenum is tight enough that I can't imagine any appreciable amount of air would come from the house. I just don't think it's worth worrying about how much.

I would select your stove based on other factors, as long as it has an OAK available. It will be fine.

I do wish that Woodheat.org article would be at least be modified. IMO, it does more harm than good by scaring people away from what is a very good system and mandatory in more and more codes.

 

[John Ackerly]

Looks like Europe is a bit ahead of us on this topic. I just across a retailer in the UK who has a whole page on the details of each stove's outside air kit. Quite a few specify that they get their primary air from outside and secondary air from inside.

Hwam says: "Total seal. DibT tested for passive houses."

Moreso stoves appear more complex and not necessarily completely sealed and some need work to seal the backs.

Vermont Castings says: "However this is not totally air sealed as a little air can get into the stove from the room."

Here is the link for long list of stoves, only a few of which are sold in the US:
https://www.stovesonline.co.uk/direct-air-supply-stoves.html.

 

[Smoked]

First thought, why provide an OAK inlet if all combustion air is not supplied through it??? From comments above, I guess all manufacturers don't feel that way.

 

[JA600L]

The Ideal Steel Hybrid does not have an oak hookup for the cat air supply.

 

[CenterTree]

Thanks for these links. I often end up at your site and find great info there. (What's with the black background though?).
Do you know any way of telling which stoves only take air from the OAK, and not the room? Woodstock Soapstone does that apparently in their Absolute Steel Hybrid, but surely there are others. Seems like there should also be a voluntary test that the EPA accredited labs can do that can prove to consumers that the stove can't take indoor air.

It isn't CenterTree's site. It belongs to Tom Oyen. Forum member "thechimneysweep" .

Thanks Bart!

OP: (John) Just to be clear.... I merely posted some useful info.
That site is from another member here and it has always helped me a great deal by providing useful info on wood burning.

 

[branchburner]

It is not the stove that determines if you need the door open to start it is the draft.

I'm not sure this is completely true. In my Oakwood, for example, there was no baffle... so with the bypass open, that stove was easier to start cold with no open door than either the Jotul or the Woodstock seemed to be.

The burn technology and configuration of the stove is going to play some role in how effectively a given level of draft pulls through the firebox, isn't it?

 

[bholler]

I'm not sure this is completely true. In my Oakwood, for example, there was no baffle... so with the bypass open, that stove was easier to start cold with no open door than either the Jotul or the Woodstock seemed to be.

The burn technology and configuration of the stove is going to play some role in how effectively a given level of draft pulls through the firebox, isn't it?

Yeah you are right that will play some role also.

 

[begreen]

Stove construction has a lot to do with this. Many stoves have boost air manifolds that direct a little air at the base of the fire. Some have separate startup air control to do the same thing. Also, the way that the air supply is ducted will affect how much draft is needed to supply air to a starting fire and as it warms up, to the secondaries.

 

[Poindexter]

I have been reading up quite a bit lately as the wife and i have an offer in on an empty we would like to retire to.

The eu spec "passivehaus" certification is very attravtive to me becuase such a huge portion of my home energy use is for heat.

The bugaboo in the passivehaus spec that is largely unadressed in north american standards is sealing. To earn "passive haus" you close all the doors and widows, install a vacuum pump in a convenient window and see how much vacuum can be drawn before air leaks into the home theough whatever joint is least tightly sealed.

No outdoors exhaust over the cook stove, youd be lucky to draw 0.001 inches of water vacuum.

I think this testing is the source of the op question.

 

[Poindexter]

At 5 star energy efficiendcy now i am right on the cusp of needing an hrv to maintain in dor air quality.

Saving money on the heat bill is good, but going to a tighter house i would have to have an hrv system, and a generator to keep the hrv running during power outages.

Mold abatement ( when not if i think) would be a MAJOR pain in the tuckus.

 

[Poindexter]

From an indoor airquality perspective, letting even one particle of smoke into the house is problematic because indoor air turnover is so slow.

The compromise option i looking at is meeting passivehaus beore the cook stove exhaust and wood stove chimney are installed.

From there i am toying with an opable door on the cook stove exhausr outlet, an oak that seals pretty good, with the hrv plumbed to drop fresh air near the stove when the wood stove door is closed - and an hrv inake near the stove to pump smoke out while the wood stove loadibg door is open.

 

[Sprinter]

I'm mostly replying to this thread to follow it, but one question I have is, how many CFM of combustion air are you using when considering a design for an hrv system, etc? Being down here in more moderate climate, these things don't come up that often.

It just seems to me that any interior leakeage from a decent OAK stove would be nearly meaningless, but I'm willing to learn. It seems that a specific CFM quantity would be essential.

Sorry if the thread is going astray. I'll bow out if so.

 

[Sprinter]

Many stoves have boost air manifolds that direct a little air at the base of the fire.

This description seems to apply to my stove (PE 27). The air seems to flow nearly laminar to the base of the fire, allowing it a quick build-up. No need for a cracked-open door at all. If anything, the open door usually hinders the fire (at first) because it's too vigorous and seems to have a cooling effect. Very occasionally, I'll crack the door open for a minute, but that's usually because I've loaded it poorly.