Can you get outside air by going up?

Just wondering what is wrong with the air in the room ??????

thats to expensive to burn!

just kidding thinking the same. an OAK for a fireplace...interesting

pcampbell said:

We have an odd old 70s steel fabricated fireplace. I am wondering if we can replace it with something that would take outside air by going up the chimney rather than using room air? We cannot go left, right or down for outside air (it's on the inside wall of a condo). Thanks.

Click to expand...

Clever idea.

No, if you're careful to:

Maintain all clearances to the chimney (usually 2" minimum)

Keep the intake pipe as far as possible from the chimney, so it stays as cool as possible and doesn't cool the chimney.

Position the intake far enough from the chimney outlet to ensure you don't suck in exhaust gas.

Use a relatively large pipe--I'd suggest 4"--to keep frictional losses down over its relatively long run.


The intake might initially draft the wrong way on startup, since it's a little warm and acting as its own chimney. But, if you do the above, the instant your stove starts drawing air through it (e.g. you close the stove door) the intake will cool down and stop sucking the wrong way.

shawneyboy said:

Just wondering what is wrong with the air in the room ??????

Click to expand...

Lookup OAK or outside air kit. Lots of implications and discussions. It's been discussed a lot, and I don't want to hijack this thread.

HTH, and good luck.

an OAK is most likely not needed unless the condo is really tight. I am assuming it is not since there is an older unit there, so the question then becomes why go with an OAK and "what is wrong with the air in the room?".

If you have a 70's pre-fab fireplace, no amount of make up air from outside is going to overcome the stove just shooting the heat up the flue.

pcampbell said:

I guess what I am asking is can we replace the whole thing with something that takes outside air without going left/right or down (we can't go in these directions). i don't care about keeping the existing thing.

I thought that outside air is an important part to not sucking up conditioned air and sucking in cold air from outside?

Click to expand...

Hey PC,

Yes it is, IMO. It's a matter of some debate, but yes, as you know, the idea is to not suck up the just-heated air from the stove, to be replaced by cold air leaking in and cooling peripheral areas and creating drafts towards the stove. You also lessen lost humidity, that burners often combat with pots of water on their stoves, and humidifiers. I didn't want to sidetrack the thread, since you are asking about how to do an OAK, not what they're for.

And yes to your first question, as in my previous post. I can't think of any problems if you do it right.

HTH

I think the short answer is no. You need as much air going out as is coming in. The chimney was designed to be large enough to allow sufficient capacity for the exhaust going out. This is usually a bare minimum cross-sectional area of 1/10 of the fireplace opening. By running an air supply pipe in the same flue, you would cut your exhaust carrying capacity in half, even more when you consider that round pipe will further reduce the available venting area.

pcampbell said:

We have an odd old 70s steel fabricated fireplace. I am wondering if we can replace it with something that would take outside air by going up the chimney rather than using room air? We cannot go left, right or down for outside air (it's on the inside wall of a condo). Thanks.

Click to expand...

You say that you can't go down, is there a condo under yours? If not why not go through the basement then to an outside wall. Also I think what your looking for if your looking to improve efficency is an insert, which is basically a wodd stove designed to go into a fireplace. You'll probably have to look for just the right one using a fabricated fireplace though. With these they are much more efficent than any fireplace so you won't really need an outside air kit as they don't send as much air up the chimney to begin with.

Battenkiller said:

I think the short answer is no. You need as much air going out as is coming in. The chimney was designed to be large enough to allow sufficient capacity for the exhaust going out. This is usually a bare minimum cross-sectional area of 1/10 of the fireplace opening. By running an air supply pipe in the same flue, you would cut your exhaust carrying capacity in half, even more when you consider that round pipe will further reduce the available venting area.

Click to expand...

Oh man, is he talking about running an outside air intake *inside* the flue? If so, you're completely right--don't do it! My comments were for running an outside air pipe inside the same *chase* as a separate flue pipe, outside the flue. Good catch, BK.

Which is it, PC?