How do you stop EPA stoves from drafting when not in use?

[FGZ]

Unfortunately I don't get to tend my insert often enough throughout the day to keep a fire going 24/7. So when the insert is cold, the oil FHA furnace is on. Since EPA stoves don't seal up completely, how do I keep my pricey (oil-made) hot air from going up the flue?

 

[Todd]

I use to stuff some insulation up in the exhaust collar above the baffle.

 

[ControlFreak]

My opinion only:

I doubt that the tiny amount of air that sneaks up your chimney when the stove is cold will ever make any difference. If you're that concerned about this, you would be best served to get an outside air kit on your stove (OAK), so you are not sucking in cold air when your stove is actively drafting.

 

[BrotherBart]

If you stuff something up in that flue collar for darn sure make sure that there is something like a red rag or something on a string hanging down in the firebox. If somebody comes along and starts a fire in that thing not knowing it is plugged ya got a major problem on your hands.

 

[BrowningBAR]

Unfortunately I don't get to tend my insert often enough throughout the day to keep a fire going 24/7. So when the insert is cold, the oil FHA furnace is on. Since EPA stoves don't seal up completely, how do I keep my pricey (oil-made) hot air from going up the flue?

This isn't a fireplace you are dealing with. The amount of air that is going into the stove when it is cold is minimal.

 

[corey21]

Theirs no use in blocking your flue off and when you forget that it is blocked and go to build a fire hmmm.

 

[Highbeam]

To answer your question, an OAK will prevent any heated and humidified inside air from escaping up your flue during fires and during times of no fires. This is one benefit of the OAK.

I do agree that the air flow is relatively minimal when no fire is burning but I've also spent weeks air sealing my home to try and eliminate even the smallest air leak. Same thing with the stove, it's an air leak.

Without an OAK there is no way to shut off primary or secondary air supplies to your chimney and it will always be drafting.

 

[LLigetfa]

Ja, install an OAK with a positive shutoff.

 

[precaud]

Ja, install an OAK with a positive shutoff.

Many/most stoves have separate air inlets for the secondaries which aren't always fed by an OAK.

 

[FGZ]

I thought an OAK w/ positive shutoff would only close my secondary air, while the primary still leaked a little. But taking y'alls comments in, maybe it's not drafting much while not in use. I'll get some incense to test, my initial impression that it's drafting is because I can hear the wind whip around the chimney cap and assume it's pulling my hot air out with it. If it is an issue, some highly visible rags shoved into the flue above the baffle can do the trick till something more sophisticated comes along.

 

[jharkin]

To answer your question, an OAK will prevent any heated and humidified inside air from escaping up your flue during fires and during times of no fires. This is one benefit of the OAK.

I do agree that the air flow is relatively minimal when no fire is burning but I've also spent weeks air sealing my home to try and eliminate even the smallest air leak. Same thing with the stove, it's an air leak.

Without an OAK there is no way to shut off primary or secondary air supplies to your chimney and it will always be drafting.

If an air leak as small as the 1 or 2 sq in of the stove air inlet really makes a difference in your house, then you probably should be installing a positive ventilator system to get enough fresh air for the inhabitants.

 

[LLigetfa]

Ja, install an OAK with a positive shutoff.

Many/most stoves have separate air inlets for the secondaries which aren't always fed by an OAK.

Well... I cannot speak to "many" or "most" and the jury is still out on what is "primary" and what is "secondary" but, IMHO if a stove is designed to have an OAK, it stands to reason that said OAK would provide the lion's share of air and that "other" air sourced from inside the home would be considerably less.

My stove has a 4 inch OAK supply and the internal "zipper" air a mere 3/8ths of an inch.

There are some stove models that don't have a tight seal on the OAK and as such, they could leak a lot of cold air into the home if they don't have a positive shutoff, so there is not one right answer.

 

[precaud]

All I'm saying is, don't assume that an OAK with positive shuttoff will close all of the incoming air supplies. I've examined the air systems of quite a few EPA stoves and most of them have separate inlets for primary, secondary, and doghouse air which are not all in a sealed environment fed by the OAK inlet. Examine the stove in question to see if it will or not.

 

[FGZ]

To answer your question, an OAK will prevent any heated and humidified inside air from escaping up your flue during fires and during times of no fires. This is one benefit of the OAK.

I do agree that the air flow is relatively minimal when no fire is burning but I've also spent weeks air sealing my home to try and eliminate even the smallest air leak. Same thing with the stove, it's an air leak.

Without an OAK there is no way to shut off primary or secondary air supplies to your chimney and it will always be drafting.

If an air leak as small as the 1 or 2 sq in of the stove air inlet really makes a difference in your house, then you probably should be installing a positive ventilator system to get enough fresh air for the inhabitants.

This is probably one of the most valid points - my house is nowhere near that tight. I have several projects' worth of weatherstripping before the stove is my worst draft offender. And maybe by the time that happens I could already have an OAK in place to solve part of or most of that problem.

 

[LLigetfa]

All I'm saying is, don't assume that an OAK with positive shuttoff will close all of the incoming air supplies. I've examined the air systems of quite a few EPA stoves and most of them have separate inlets for primary, secondary, and doghouse air which are not all in a sealed environment fed by the OAK inlet. Examine the stove in question to see if it will or not.

Again, I dare not be so liberal with the term "most stoves". Rather than speak in generalities, perhaps someone well versed in how the Jøtul C450 gets its air could chime in here and set FGZ on the right track.

One other point with an OAK... even if it has a tight seal to the stove and provides the lion's share of air, that air is still very cold and as such may turn the stove into a chunk of frosty cold steel that still sucks heat out of the house. The flue will draft mostly from the heat rising through it and not from the wind wistling past the cap. If the house has a pressure deficit, the OAK will push more cold air into the stove than the draft could suck warm room air. In my case that resulted in frost appearing on the glass and metal and lots of condensation elsewhere. A positive shutoff cured that.

 

[krex1010]

I may be way off here, I am not an expert in any of this. But how much air can a cold EPA stove really be leaking? It's not like the older stoves where the air feed is a direct opening into the firebox, the air has to take a route through the back of the stove then is directed through small openings into various points in the firebox, right? The fire is basically the engine that drives the draft in a woodstove right? So take away the fire, what is going to force air to take that route through the stove and up the chimney? I hear of people that have to preheat there flue's to get a draft going and some people who have really airtight homes have to crack windows or turn their forced air systems off to get their stoves to draft. People have trouble getting heat to work it's way through their home, so why would heat work it's way through a cold woodstove? Warm air really has a hard time displacing cold air so even if some small amount of air made it's way through the air intakes on the stove would it even come close to being able to displace the plug of cold air in the chimney so it can escape and create a draft? Anyways I think I rambled enough here, am I wrong in my thinking here?

 

[LLigetfa]

But how much air can a cold EPA stove really be leaking?

I cannot say what the Jøtul C450 would let by when closed down but in the case of my RSF, the butterfly on the air control has a one inch square notch in it. The rest of the formula depends on how much the flue draws and how much pressure deficit there is at the stove. A home could easily leak more than one square inch at a single window, attic hatch, or plumbing stack. A poorly installed OAK could (would) make it worse instead of better.

Now an operating stove is another matter. The much higher heat going up the flue induces draft and the larger air opening results in much more air being drawn.

 

[firefighterjake]

Minimal heat loss . . . I suspect I lose more heat in the home every time I open the back door to either go pee outside (it's a guy thing) or to get more firewood than I do through the woodstove . . . although I do tend to heat 24/7 so there generally isn't a whole lot of heat loss due to that fact.

 

[midwestcoast]

To answer your question, an OAK will prevent any heated and humidified inside air from escaping up your flue during fires and during times of no fires. This is one benefit of the OAK.

I do agree that the air flow is relatively minimal when no fire is burning but I've also spent weeks air sealing my home to try and eliminate even the smallest air leak. Same thing with the stove, it's an air leak.

Without an OAK there is no way to shut off primary or secondary air supplies to your chimney and it will always be drafting.

If an air leak as small as the 1 or 2 sq in of the stove air inlet really makes a difference in your house, then you probably should be installing a positive ventilator system to get enough fresh air for the inhabitants.

This is probably one of the most valid points - my house is nowhere near that tight. I have several projects' worth of weatherstripping before the stove is my worst draft offender. And maybe by the time that happens I could already have an OAK in place to solve part of or most of that problem.

Although I'm a bit obsessive about air-sealing, the most I do is close the primary air down when the stove is not in use & call the rest insignificant.

You may know already, but the worst air leaks are ussually the ones that are somewhat hidden. The plumbing stacks, chimney chase, stud wall footer & header areas, poorly built & unsealed ducting, knee-wall to floor joist & side attic connections, open soffits.... The smaller stuff like electrical penetrations & recessed lights can also add up 'cause there are so many. I've found air leaks better measured in square feet than inches in this place.
Aside from things connected to the chimeny, air leaks in the lower (basement) & upper (attic) portions of a house will leak more air per sq inch because there's generally a slight low pressure down low & high pressure up high in a house in winter. Leaks like windows & doors in the living space are often less important as they're in tha more neutral pressure zone, but they are right there where you can see & feel them.

 

[Hogwildz]

If you have a shut off on the OAK, does the airlfow come from the house then anyway?

 

[LLigetfa]

That would depend on the stove model and how well the OAK seals to the stove. On mine it would nearly snuff out the fire and turn it into a nasty smoker, blackening the glass. Don't ask me how I know.

 

[Hogwildz]

I mean from a manner if the stove is not lit or burning, and the OAK is closed down, I suppose depending on how tightly the OAK closes & seals.
Would the any natural draft occur where the draft of air would come from the warm house air, much like a stove w/o the OAK?
And also curious, does a stove with OAK still get down draft effect from the stack when cold? With or without the positive shut off engaged?

 

[LLigetfa]

If there is not a good seal between the OAK and the stove, a fully closed OAK would not prevent room air from going up the flue. Again though, I can't imagine very much air going up the flue on a cold stove that is closed as far as possible.

As for reverse drafting, that is usually caused by stack effect whereby the house has a pressure deficit which counteracts the weak draft on a not so hot flue. I can't imagine an OAK with a good seal on a cold stove reverse drafting as there should not be much if any pressure deficit between the OAK inlet anf the flue outlet except in very rare wind conditions. While rare, it is possible and that is why the OAK install should factor a possible flue reversal on startup that could push hot gasses out the OAK.

If the OAK to stove connection is not well sealed, or the stove has alternate air intakes to the room, the presence of the OAK will not prevent a pressure deficit from reversing the flue.

I've said it before and I've said it often that an OAK in and of itself will not cure a pressure deficit situation entirely. The building needs to be factored in the overall design and operation of the OAK/stove.

 

[buckstove]

I've had the same opinion on losing air when not in use but just said forget it and decided not to worry about it. When summer gets here I might try to come up with something if i'm afraid I might lose might precious cool air from my AC. But I did put in an OAK during install.

 

[CHIMENEA]

I'm going through the same problem with my insert. Was replacing insulation in the crawlspace today so I've been keeping an eye on the thermostat lately to see how the temp is holding. Sitting here ~8ft in front of the hearth, and notice a draft in the air. I can't figure where it could be coming from, thought I was sealing up the last of the 'big' holes under house this afternoon.

Get up, walk toward the insert, kneel down on the hearth, and bam. The hearth is ice cold, cold air is down drafting out of the bottom blower intake louvers. Bummer, cold air is coming out at varying speeds up to the same force as the blower on low speed.

Weather channel has it at 32*, NNW17mph. Maybe it won't be as noticeable with lighter winds.