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Old 01-15-2011, 03:08 PM   #1
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Heat loss over shower stall


You can see, from the snow melt picture, that there is heat loss through the ceiling and roof. This snow melt spot is directly above the shower stall - not the ceiling outside the stall.

This was a 7" snowfall, last weekend, which is very unusual for northern Alabama.

The house was built in 1963. In 1985, roughly, we had some blown-in fiberglass insulation added, in the attic, on top of the original 5 inches of rock wool. That got us to a total of about R35.

I have never been to the part of the attic above the shower - so I don't know how the shower stall was framed, whether it has a vapor barrier above it or whether there is any insulation above it.

There is no vapor barrier in the attic, in the areas that I have access to, such as the one in the attic picture. There are no HVAC ducts in the attic.

This bathroom is not vented, but we don't get mold problems - maybe because we leave the door open to the bedroom while showering.

This is not a new issue. Whenever we get frost on the roof, the same spot is the first part of the roof to get defrosted.

What could be causing this heat loss - and is it something that should be fixed?
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Heat loss over shower stall-snow-melt-over-shower-stall.jpg   Heat loss over shower stall-attic-insulation.jpg   Heat loss over shower stall-shower-stall.jpg   Heat loss over shower stall-shower-top.jpg  

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Old 01-15-2011, 03:19 PM   #2
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Heat loss over shower stall


#1 is always AIR sealing. You'll have to get in there and see why so much air is passing from the shower up to the roof, and, no, that is not good at all and, yes, that should be fixed. Insulate while you are in there air sealing. Moving air carries heat and moisture into the attic. A vapor barrier is probably not necessary in Ala, but air barriers are. No fan? You should install a fan asap, if at all possible.

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Old 01-15-2011, 04:56 PM   #3
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#1 is always AIR sealing. You'll have to get in there and see why so much air is passing from the shower up to the roof, and, no, that is not good at all and, yes, that should be fixed. Insulate while you are in there air sealing. Moving air carries heat and moisture into the attic. A vapor barrier is probably not necessary in Ala, but air barriers are. No fan? You should install a fan asap, if at all possible.
There is only one noticeable possibility of an air leak inside the house. It's a crack in the gout between the tiles of two walls inside the shower. I did a smoke test and there was no air being pulled into that crack.

Could it be that the tiles of the shower are conducting heat into the attic - and - if there is no insulation, or 'failed' insulation, above the shower, the heat goes quickly to the roof?
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Old 01-15-2011, 06:35 PM   #4
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Heat loss over shower stall


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There is only one noticeable possibility of an air leak inside the house. It's a crack in the gout between the tiles of two walls inside the shower. I did a smoke test and there was no air being pulled into that crack.

Could it be that the tiles of the shower are conducting heat into the attic - and - if there is no insulation, or 'failed' insulation, above the shower, the heat goes quickly to the roof?
Is your shower stall ceiling built down? I'd put an exhaust fan inside the shower (will need to gfci connected) and exhaust it outside. You also need to make sure the attic vents are working properly. Deal with the moisture removal first, then the insulation. Eventually you could have a mold problem which is worse than a heat loss problem
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Old 01-15-2011, 07:13 PM   #5
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Is your shower stall ceiling built down? I'd put an exhaust fan inside the shower (will need to gfci connected) and exhaust it outside. You also need to make sure the attic vents are working properly. Deal with the moisture removal first, then the insulation. Eventually you could have a mold problem which is worse than a heat loss problem
There is about 18" between the top of the shower and the ceiling in the bathroom. You can see it in the pictures.

Can a lot of moisture actually get through the tile of the shower and up into the attic? I'd have thought that a lot more of the shower's moisture would go up through the sheet rock ceiling of the bathroom.

The attic vents are working. It might be that the blown in insulation has walled-off the area above the shower, all the way to the roof, which isn't very far up. But, that wouldn't explain why there is less heat loss above the rest of the bathroom - especially between the shower and the outside wall.

Could the way the shower was framed have anything to do with this?

Last edited by John_W; 01-15-2011 at 07:20 PM.
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Old 01-15-2011, 07:47 PM   #6
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Heat loss over shower stall


You may have to cut into the Gypsum above the entrance of the shower to get a good peek. Plus it would allow you to see how hard it will be in getting the fan up there. There are remote fan units, where you would place the vent in the shower, but the fan would be away, so as not to make so much noise in the shower area. Unless you can find a midget or a small kid to crawl over that way with a camera, it will be hard to see from the attic space.

To the left, is that the ductwork for the Furnace, or just a Soffit that was built in that section?
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Old 01-15-2011, 08:00 PM   #7
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You may have to cut into the Gypsum above the entrance of the shower to get a good peek. Plus it would allow you to see how hard it will be in getting the fan up there. There are remote fan units, where you would place the vent in the shower, but the fan would be away, so as not to make so much noise in the shower area. Unless you can find a midget or a small kid to crawl over that way with a camera, it will be hard to see from the attic space.

To the left, is that the ductwork for the Furnace, or just a Soffit that was built in that section?
Good idea about cutting through the wall above the shower to see what's 'going on' up there. I agree about it being hard to get to that spot through the attic. Very difficult and messy.

The pipe to the left is a plumbing pipe. Its connects, down in the crawl space, to the toilet discharge pipes. Probably something about keeping sewer gases out of the interior of the house.
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Old 01-15-2011, 08:17 PM   #8
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Heat loss over shower stall


Not on the roof, I am talking about the Soffit above the plumbing access in the third picture.
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Old 01-15-2011, 09:09 PM   #9
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Not on the roof, I am talking about the Soffit above the plumbing access in the third picture.
We put a fluorescent light fixture on the ceiling, over the sink/commode. What you see is the box we had built around and below the fixture, to hide it but let the light through.

No holes were made in the walls or ceiling.
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Old 01-16-2011, 10:47 AM   #10
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You may have to cut into the Gypsum above the entrance of the shower to get a good peek. Plus it would allow you to see how hard it will be in getting the fan up there. There are remote fan units, where you would place the vent in the shower, but the fan would be away, so as not to make so much noise in the shower area. Unless you can find a midget or a small kid to crawl over that way with a camera, it will be hard to see from the attic space.

To the left, is that the ductwork for the Furnace, or just a Soffit that was built in that section?
Suppose I open the wall above the shower and there is no insulation or 'failed insulation' up there. Is it OK to put new insulation in there? What kind and how much?
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Old 01-16-2011, 10:55 AM   #11
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Heat loss over shower stall


RoxWool would be the best. I would right now look at it as the aspect of investigation. Get the hole cut, and take some pictures. Now also, where the pipes are for the shower, even just blocking the convection process on that side with Roxwool would be a plus first, then see from there. Humidity rises through air movement process, heat through the convection process.

Also, if you can get to where the shower is and take photos up in the attic of the wood sheathing, that would show everyone if there are other problems in that area. Even if you can get a vent fan into the bathroom and either vent through the side of the house, or through the roof, that would be a start and something to put on the list for Summer.
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Old 01-18-2011, 03:52 PM   #12
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Heat loss over shower stall


Is that plumbing access or some sort of medicine cabinet in the third picture? Can you use that to get a look up through the wall?

It is likely that the soffit above the shower is open to the attic and to the inside of the neighboring walls between the studs. Air is heated within those walls or leaks into those walls and rises up to the soffit and into the attic.
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Old 01-19-2011, 03:47 PM   #13
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Is that plumbing access or some sort of medicine cabinet in the third picture? Can you use that to get a look up through the wall?

It is likely that the soffit above the shower is open to the attic and to the inside of the neighboring walls between the studs. Air is heated within those walls or leaks into those walls and rises up to the soffit and into the attic.
It's where we accessed the pipes in the wall behind the shower, to fix a leak, but it's not easily opened. I didn't like the flimsy snap in approach to covering the hole so I put sheet rock in and framed the resulting cut lines with the molding you see.

Thanks for the air heating theory. That's what I think too.

I will probably open the soffit above the shower for the best possible view - and as a way to make any needed fixes.

I'm still not clear on what to do - assuming it's just hot air rising from inside the walls and the top side of the shower - into an open, unobstructed, uninsulated part of the attic. I want to stop the airflow, insulate to slow heat transfer and do it without creating a moisture problem of some kind.
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Old 01-19-2011, 07:19 PM   #14
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Heat loss over shower stall


Install Bathroom Vent, and then try to get to the top of the shower, and make sure there is enough insulation on top of the space in the Attic.
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Old 01-20-2011, 11:28 AM   #15
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Install Bathroom Vent, and then try to get to the top of the shower, and make sure there is enough insulation on top of the space in the Attic.

OK. The bathroom vent would suck all the moist air from the shower out. So, with that installed, the worry about moisture rising from the shower into the attic goes away.

Then, to deal with daylong heat rise from the interior of the shower stall cavity, I can just shove some insulation into the soffit over the shower, with no air barrier? Or, do I need to install an air barrier above the shower stall, and put the insulation on top of the air barrier?

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