Comments on: Two Open Doors to the Attic – A Building Science Nightmare

By: James Howison

James Howison — Fri, 15 Jun 2012 01:46:08 +0000

Hmmmm, I have a situation
Hmmmm, I have a situation that might be similar and might not. We have a naturally-combusted gas furnace in a mechanical room, but the water heater isn't there. There is air-intake in the closet door but it's at ground level; it's the return for the ducting system. In theory the rest of the closet is air-sealed from the conditioned space (I'm working to improve that).

There are two issues here. The first is air-sealing. Does it matter if the air-barrier is at the door or at the ceiling of the closet (where it can never be since one needs combustion air)? Seems to be that sealing the closet is all that's required, in my situation.

The second is radiant heat from the roof down into the closet (I should say that we're a cooling dominated climate) onto the top of the plenum and the air handler. That's really more of a "ducts inside conditioned space" thing and probably would be improved by covering the top of the closet, but above the plenum (remembering to provide combustion air still).

In a heating situation (we get those sometimes ;) I think it's much obviously problematic, since the cold air in the attic will sink into the closet (probably won't notice when the furnace isn't running), creating a radiant heat sucking cool stack in the middle of the house. I'm assuming that the closet is open at the top but otherwise well air-sealed (like mine, not the one in the picture).

Am I thinking about this right?

By: Debbie

Debbie — Tue, 12 Jun 2012 18:51:53 +0000

common here in La. also.&
common here in La. also.

usually heating system in same interior closet..all open to attic.

last house had a huge thermal bypass at fireplace, on top where you could see firebox & interior of sheetrock walls as expected. the ceiling changed heights from living room with fireplace to bedrooms. at this kneewall there were 5 open joist bays with batts stapled in place. $8.00 sheet of sheetrock, a little caulk and all sealed up. took longer on top to cut the sheetrock to fit and seal between ceiling joists. 700 cfm leakage from this room down to 120 cfm. (still needed to caulk brick at fireplace to walls inside house)

thermal bypasses are pretty common at details in master bathrooms & foyers in my area...just gotta look for them!

By: Robert J Susz

Robert J Susz — Tue, 12 Jun 2012 00:45:23 +0000

I see this in a retirement /
I see this in a retirement / group home community all around Rochester, NY. The mechanical rooms have a 6" duct that runs vertically 1, 2, or 3 stories up to the attic.

I was told it is for makeup air and was required by code.

"Besides, don't worry about this. You're not here to look at makeup air; You're here to look at ice damming."

Not to mention the gas bills for a 600 sf apartment were higher than those for my 3000 sf house.

-Rob

By: Jamie

Jamie — Mon, 11 Jun 2012 22:32:25 +0000

I see this kind of thing here
I see this kind of thing here in KY all the time. In many cases it's the only reason the family has not died of co poisening, because a poorly installed furnace and a gas water heater cramned into a little space almost always spells back drafting especially in cooling season when there is no gas to aid the water heater in venting. My soultion is go all electric because "Gas go Boom!". Also nice New Balances!

By: John Nicholas

John Nicholas — Mon, 11 Jun 2012 17:05:23 +0000

I have seen a slightly
I have seen a slightly different arrangement 3 times on audits. The DHW is partially in the house and partially in the attic. The homeowner on the first one was very proud that he did not have to bend over to light the pilot light. When I got to the attic, I found the work he had done to air seal.

http://dl.dropbox.com/u/20018953/DHW_Attic.JPG 

Glad to know it is not just a Wichita thing. Sorry to see it happen at all!

By: Dennis Brachfeld

Dennis Brachfeld — Mon, 11 Jun 2012 15:58:47 +0000

We find this fairly common
We find this fairly common with hot water heaters, and furnaces in condo and apartment closets. If below attic,we run combustion air ducts into attic with "cold air loops" (like P or O traps), line the vented door and seal and insulate the the ceiling, not the walls (we are a heating climate here in Denver CO . If over a crawl space we run the air in from crawl space vent, also with loop. "We loop it up!" (cold air traps)

By: david gano

david gano — Mon, 11 Jun 2012 14:11:22 +0000

Could this be another So
Could this be another So called Passive House failure? Dave Gano