Soffit Cold Air Intake (Above Wood Stove Firebox?)

[billwill.julz]

Hello, all! I just want to say that from information I have learned on this forum, I have installed a Supervent chimney in our new construction, slab on grade home. We are planning for the Vermont Castings Dauntless with a cold air intake. Everything is looking great, however, I failed to plan ahead when pouring the slab and did not install a solid vent pipe under the slab for the cold air intake.

R1006.2 Exterior air intake: The exterior air intake shall not be located within the garage or basement of the dwelling nor shall the air intake be located at an elevation higher than the firebox."

I am unclear whether "air intake" or "exterior air intake" refers to the actual port located on the exterior wall or the entire length of the pipe.

Here is my plan: install the air intake behind the stove below the firebox, run it up the interior wall (8ft.) into the attic, over to an exterior wall (9ft.), and back down that exterior wall (8ft.) to a location below the firebox (see attached image).
Would this avoid back draft issues/competing flues and also be installed to code or does the entire length of the intake pipe need to be below the firebox?

Thanks for any and all input.

 

[begreen]

That is not a good plan. It will introduce at least five 90º turns in the outside air path which will be too restrictive. Unfortunately with the slab it sounds like the intake will end up being elevated anyway once it emerges from the slab in order to avoid getting buried by debris or snow.

It might be better to core a hole the slab and then tunnel under the slab to meet that hole. But what happens on the outdoor end of the pipe?

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[billwill.julz]

That is not a good plan. It will introduce at least five 90º turns in the outside air path which will be too restrictive. Unfortunately with the slab it sounds like the intake will end up being elevated anyway once it emerges from the slab in order to avoid getting buried by debris or snow.

It might be better to core a hole the slab and then tunnel under the slab to meet that hole. But what happens on the outdoor end of the pipe?

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Thanks, begreen.

Cutting/coring the slab is not an option as the concrete is our finished floor, plus there is hydronic tubing throughout the floor.
However, the intake would not need to be elevated as you are thinking as the slab is 10" above grade and we only get maybe max 6" snow here.

I do have another option to throw your way, but you may not like it as it involves six 90 degree turns and requires reducing the pipe size to ~2" in order to be fed through non-load bearing 2x4 walls. (see attached)

The benefit here is that the total length is ~17 ft. (whereas the attic plan has a total length of ~27 ft.) and the pipe never exceeds the elevation of the firebox.

Do you think either plan would suffice or should accept the loss and abandon the cold air intake idea altogether?

Thanks,

 

[begreen]

That's even worse. The extra elbows would be even more constrictive. Reducing the pipe size is the opposite of what is needed.

As long as there is an air gap in the air supply right before the stove, the risk of backdrafting is eliminated. It looks like the cleanest route then is this shortest route with the air vent at the wall, right behind the stove.

 

[billwill.julz]

That's even worse. The extra elbows would be even more constrictive. Reducing the pipe size is the opposite of what is needed.

As long as there is an air gap in the air supply right before the stove, the risk of backdrafting is eliminated. It looks like the cleanest route then is this shortest route with the air vent at the wall, right behind the stove.

View attachment 335948

Thanks. That green route is actually through a passage/entranceway.