Thread: Furnace Closets

For a 1986 home, the furnace closet ceiling are open to the attic. Gas to the furnaces are installed.

Is the ceiling open to the attic a defect ?

thanks,

bm

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Originally Posted by brianmiller

For a 1986 home, the furnace closet ceiling are open to the attic. Gas to the furnaces are installed.

Is the ceiling open to the attic a defect ?

thanks,

bm

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Ceiling open to the Attic is where the combustion air for the gas fired appliance is coming from.

No defect .
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If the furnace closet is considered part of the conditioned space then it is a defect and should be corrected.

Originally Posted by DavidR

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If the furnace closet is considered part of the conditioned space then it is a defect and should be corrected.

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Agreed.

Sealed Supply Closet Door is required.
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I see many split systems in my area that have the A coil & Furnace in the hall closet open to the unconditioned space above.

Most easily idenified by the return vents located at the bottom of the closet and usually a return vent on each side located in the a jointing rooms.
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Furnace closets often have what I call an identity crisis. Basically, is it indoor space or outdoor space?? Many I see are drawing combustion air from the attic or crawl space (outside) as well as the inside (usually through louvered doors). I never understand how many installers screw this up, even on new construction.

Make a commitment one way or another.... either one is fine.... just decide which one it's going to be. You can't do both. If you're going to draw combustion air from outside use exterior doors for the access and weather-strip them. If you're drawing combustion air from the inside there can't be openings into the outside spaces and the surronding walls have to be insulated.

I always love it when I find an insulated wall with a louvered vent in it (see picture)

There are two schools of thought on this:

1) Close the ceiling off, insulate the ceiling, then put two 12" holes through the ceiling for combustion air ... does not make a lot of sense to insulate the ceiling then put two 12" holes through it.

2) Leave the ceiling open and you have just make it better ... but how does leaving the ceiling open make it "better".

IF you do either, the walls really should be insulated and sealed as those walls, and the door to that closet, are now the perimeter of the thermal space and not the ceiling (or lack of) for that space.

If a return goes into that space, the return should be ducted directly to the return on the equipment and not left open to that space. That space is communicating with the attic, which is considered outside the thermal envelope, and thus that space is outside the thermal envelope.

One furnace closet in the upstairs hallway of the house has an open ceiling to the attic. For this one, my comment will be to just seal the closet door to the living space.

The other furnace closet in the upstairs hallway of the house has the ceiling closed, but no combustion air venting. I'll recommend combustion air venting installed and the closet door sealed.

Thanks,

bm

Originally Posted by brianmiller

One furnace closet in the upstairs hallway of the house has an open ceiling to the attic. For this one, my comment will be to just seal the closet door to the living space.

The walls around that furnace closet will need to be insulated to the R-value of the attic insulation.

The other furnace closet in the upstairs hallway of the house has the ceiling closed, but no combustion air venting. I'll recommend combustion air venting installed and the closet door sealed.

I would recommend combustion air venting to the interior, and a louvered door, not sealed.

As soon as you but combustion air vent through to the attic you almost might as well open the entire ceiling and treat the same as the first one.

In fact, I would recommend a ceiling be installed for the first one, with ceiling insulation, and combustion air venting to the interior including a louvered door ... for the reasons given.