outside air intake duct

I read about it but it is for freestanding stoves and not my insert. I think there is a knockout on the bottom somewhere and then a plate that screws on to block off the inside air...I think...never investigated any further - until i decide to put some legs on this thing.

Anyway, the benefit is that you will be filling the house with warm air from the stove / blower as opposed to, in addition, sucking cold air in from outside. Should help keep the house warmer.

Without an outside air duct to feed your stove combustion air your stove must use indoor heated air for combustion. As that air is burned and exhausted through your chimney new air is sucked into your living space through the cracks in your envelope. Cold outside air.

The outside air connection is a requirement in Washington and elsewhere.

But, if you pull it through the cracks/crannies you are diluting the warm air inside the envelope. With an OAK (outside air kit) you pull the cold air directly into the stove without cooling the room.

Don't confuse combustion air and fan air. That is, combustion air is going to go out the chimney, and fan air just gets pushed back into the room.

My Regency warmhearth uses outside air for combustion. It's nice to know that none of my heated room air is going up the chimney. Also, once I close the door, I don't have to worry that running the exhaust fan will suck smoke into the house.

My Fireplace XTrodinaire that I had in my last house used outside air for the fan air. Resulted in positive pressure in the house.

Yes without OAK your nice heated room air is being sucked from the room, burned, and sent up the chimney at a rate determined by your chimney's draft. This suckage pulls outside air into your home through all of the air leaks, and yes we all have air leaks. This outside air that gets sucked into the house contains very little moisture which means that your RH levels will fall. The outside air is fresh, cold, and oxygen rich. Some folks like the idea of an uncontrollable leak which exchanges old room air for new air, the rest of the folks would rather have a tight home with controllable air leaks like windows and fans.

My last stove used inside air and this new stove uses outside air for combustion. We think it is less drafty with OAK.

This is the first year that I have used a OAK. I did not want to drill a hole thru the floor or side of the house. What I did was made a board with a 3" hole in that just fits into a window. The board is insulated and the window shuts down on it. So far it has been working great and I can remove it in the Spring. The other nice thing is I don't have to worry about being around the stove as much with oxygen as it is getting it's air from outside.
Don

There's no such thing as a free lunch.

If you pull combustion air from outside, remember that you're going to have to heat that cold air a lot more than the warm air pulled from inside your house (Δt) to maintain adequate stack temperatures to prevent creosote buildup. Also, if the heat from your wood is going into heating up the combustion air, that heat is not coming out of the stove into your house. It's going into your exhaust gases. Finally, drawing cold outside air into your stove is going to have the effect of cooling your stove ... meaning that its temperature will drop, which means that there will be less of a Δt between your stove temperature and the room air temperature around it, meaning that you're going to get less heat out of the stove through convection and radiation.

All of this is a long-winded way of saying there's no free lunch. I just let the stove draw combustion air from the house. Adding a combustion air duct from ouside the house seems to me like more trouble and cost than it's worth.

Adirondackwoodburner said:

ok so what you are saying is that if I had a 'leaky house" the stove would be pulling air in through the walls anyways rather than just from one direct point source?

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If you pull combustion air from inside the house, that air is being exhausted to the outside up the chimney. That air has to be replaced somehow. Even if you don't have a leaky house, you'll still have some air infiltration. It may come through bathroom fan vents or range hood vents, or where ever it can find a way in. If not, your stove will get awful smoky due to weak draft.

-SF

The other issue is that if you have other natural draft appliances (water heater, furnace, etc.) the stove could affect their drafting or pull air down the chimney.

To elaborate on what Metal said, if you have no outside air kit, you may have to crack open a window when you do such things as use your dryer, or risk pulling smoke out the stove door when you re-load....

I have always thought that Outside Air was a safety requirement rather than a heating-performance issue. Required in some jurisdictions to avoid back-draft situations either in the stove itself, or in something else that shares the same air supply, like a gas water heater.

Eddy

DoubleClutch said:

There's no such thing as a free lunch.

If you pull combustion air from outside, remember that you're going to have to heat that cold air a lot more than the warm air pulled from inside your house (Δt) to maintain adequate stack temperatures to prevent creosote buildup. Also, if the heat from your wood is going into heating up the combustion air, that heat is not coming out of the stove into your house. It's going into your exhaust gases. Finally, drawing cold outside air into your stove is going to have the effect of cooling your stove ... meaning that its temperature will drop, which means that there will be less of a Δt between your stove temperature and the room air temperature around it, meaning that you're going to get less heat out of the stove through convection and radiation.

All of this is a long-winded way of saying there's no free lunch. I just let the stove draw combustion air from the house. Adding a combustion air duct from ouside the house seems to me like more trouble and cost than it's worth.

Click to expand...

The combustion air always comes from the outside. The only thing that changes is path it takes to get into your stove (OAK duct or through the house). If it's 20 degrees outside, the total increase in temperature from 20 degrees to combustion temp is the same. It will take the same number of BTU's to increase the temperature of the air, so the BTU loss is ultimately going to be the same in either case. The only difference is where the air is warmed up. If your house is at 75 degrees, the air is warmed up by 55 degrees in your house before being sucked into the stove. The temperature increases substantially after that.

I have a hard time believing that a difference of only 55 degrees on the intake is going to make any sort of noticeable difference in stack temperatures.

I for one would prefer to make the increase all happen inside the stove instead of sucking cold air into the living space. The OAK could potentially make a difference in how comfortable your house feels under the right circumstances.

My stove is a little over sized for my house (30-NC in a 1600sq/ft house), so I'm not too worried about drawing cold air in through the house.

Does anyone know what the gas temperatures are inside a stove while it's in operation?

-SF

In affect, if you don't have an OAK, you have the equivalent of an open window in your house.

Adirondackwoodburner said:

t ome your statement makes no sence?? I fill my house with warm air from the stove/blower right now? The blower sucks in air from the house (warmer that the outside) and cycles it aroudn the stove and goes back out into the house warmer.. So, I dont understand why pulling sub zero air from the outside would be better?

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Yeah - sorry about that. Was in a hurry and did not make a clear point at all...just trying to help out another Olympic user...

Anyway - questions answered.

G

One of the things about the EPA stoves is that they draw much less room air than the traditional open fireplaces. This is why, even when they use room air for combustion, they are somewhere around 70% efficient while the open fireplaces are usually close to 0% or negative efficiency.

I have a fresh air intake near my oil furnace burner intake to avoid a negative pressure in the house and I have never had my PE Vista insert backdraft.

SlyFerret said:

Adirondackwoodburner said:

ok so what you are saying is that if I had a 'leaky house" the stove would be pulling air in through the walls anyways rather than just from one direct point source?

Click to expand...

If you pull combustion air from inside the house, that air is being exhausted to the outside up the chimney. That air has to be replaced somehow. Even if you don't have a leaky house, you'll still have some air infiltration. It may come through bathroom fan vents or range hood vents, or where ever it can find a way in. If not, your stove will get awful smoky due to weak draft.

-SF

Click to expand...

Your stove runs hotter with the correct amaut of air. Cold or warm.