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Moving pipes in front of insulation but behind drywall


doublezero's Avatar
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02-26-09, 09:10 PM   #1  
Moving pipes in front of insulation but behind drywall

I'm trying to understand where exactly to situate some pipes in a bathroom. I have an uninsulated outside brick wall with old 1"x2" studs attached to it. I want to insulate the wall, put up a plastic vapour barrier and then put up sheetrock, then tile the wall.

I think I have only one choice, which is to use the 1" pink styrofoam batts which are only rated R-5. They are the only ones which will fit these studs. The problem is I am trying to understand how to get the half-inch hot and cold water pipes behind the wall. They have to go in front of the insulation but behind the sheetrock. (I don't know if they are supposed to go in front of the vapour barrier or behind it.) But there won't be enough space. I could cut 2 channels in the insulation, but then the pipes might freeze and that section wouldn't be insulated.
There is also a drainpipe for the sink which I have nowhere to put. There is no gap in the wall to put it. It is currently running sideways, well outside the former finished wall. This looks terrible and I really want to do something about it.

So this situation is creating several problems.

1. How to get 3 pipes behind a new wall so they are invisible. But the wall is not deep enough to do this.

2. I could widen the wall by replacing the 1"x2" studs with 2"x4" or something bigger. Then, the pipes would fit in between the insulation and the sheetrock. But..

3. The bathroom is extremely narrow as it is. Pushing the wall out would take up scarce space.

4. But maybe I should use thicker studs because then I could use better insulation. I'm either in zone 5 or 6 on the R-map. The map says I need R-13 to R-21 on a wall. So R-5 on an outside wall might not even be worth putting up.

This is all assuming I am not building a cabinet under the sink. The space is too cramped as it is for one.

So the H & C have to be hidden behind the wall. They will be invisible. They will only come out of the wall at the exact spot where they connect to the new faucets for the sink. I've only helped to install one sink before and it was an ugly, temporary job, so maybe I don't know enough and what I'm trying to accomplish isn't possible.

What else.. I thought that maybe I could cover the pipes with the insulation you cover pipes with and cut a channel in the regular insulation. Would that be acceptable? Or would they still freeze and let cold air in through the channel?

 
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02-27-09, 02:45 AM   #2  
I am not a contractor but to me you would want the pipes on the warm side of that wall to prevent freezing(they are in an exterior wall correct?) so they would go on the sheetrock side of your insulation. That is just my rational kinda thinking. Also like you said buy some pipe insulation and that will help prevent freezing and also keep you hot water hotter. If you do this on all the hot pipes you can turn your hot water heater temp down and save money in electric.

I know you said your bathroom is small, but why not rip 2x4's in half or even in 1/3's and attach them to your 1x2's, insulate to r-13 or something to that nature then put up 3/8 inch drywall instead of the 1/2 inch. I know you won't save a lot of room by going to a thinner drywall but something is better than nothing.

I know you said you haven't done a lot of plumbing before, so becarefull not to start a fire when fitting the copper pipes together. A pedestal sink would work best in this kind of situation where you don't have a lot of room, or even a sink that mounts to your studs and it does not have anything underneath.

Hope this helped a little.
Good Luck

 
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02-27-09, 05:04 AM   #3  
I'm not sure how much benefit the brick wall will provide, but R=5 behind the pipes and sheetrock with tile in front, they will freeze, IMHO. Part of the problem depends on where your heat source is in this small bathroom. Outside walls are your coldest and without a direct steady heat source, the inside of that wall will get very cold.

Here are some thoughts for you, recognize I can't see the space so I'm only throwing out thoughts.

Can you come up through the floor?

Can you keep the pipes below 30 inches (or just 6") and create a ledge by building out only the lower part of the wall to give the pipes more space for insulation?

Have you considered pex tubing, less suseptable to freezing and breaking. However, it will conduct less heat from warm areas into the wall.

A picture or two might help, post at photobucket.com and post the link over here.

Tell us where the pipes are coming from and where the heat is.

Bud

 
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02-27-09, 07:16 AM   #4  
Photo 1 is showing the drainpipe for the sink. As you can see, it goes sideways outside the former finished wall. This cannot happen because the bathroom is supposed to look professional when I'm finished with it. That was the whole point of hiring an architect. The architect has come up with a nice drawing of how to renovate this bathroom but now how do I do what is showing in her drawing without ending up with freezing pipes or some other kind of problem which hasn't even occurred to me yet.

Photo 1 also shows, at the bottom, where the H & C are coming from. I just cut them off 2 days ago and capped them, anticipating that I would quickly run them to their new destination, but of course, I got stuck in the details.
They used to run outside the former finished wall up through the floor. They also branched off to the former bathtub/shower which would be to the right. These pipes ran above the ceiling below, underneath the joists. They are now supposed to run through the joists, turn to the exterior wall and poke out of the finished exterior wall into the new shower. See photo 2 to get an idea of where they are supposed to go.



Photo 2



The heat source is shown at the bottom right.

Photo 3 shows the architectural plans. As you can see, the pipes are not shown and are supposed to come out of the walls only when they connect to the fixtures. The only pipe showing is the sink drainpipe and even it is entering the wall directly rather than running sideways like it does now.

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02-27-09, 07:28 AM   #5  
Posted By: Bud9051 I'm not sure how much benefit the brick wall will provide, but R=5 behind the pipes and sheetrock with tile in front, they will freeze, IMHO. Part of the problem depends on where your heat source is in this small bathroom. Outside walls are your coldest and without a direct steady heat source, the inside of that wall will get very cold.

Bud
Bud, both you and Diyplank have suggested that the pipes have to run outside the wall or they will freeze. I am willing to replace the 1x2 studs with 2x4's so the wall can be better insulated, but the pipes are going to have to go behind the wall so the bathroom looks like it does in the drawing.

With 2x4 studs, I can use the 2" R-10 foamboard, the kind that locks into the aluminum furring strips and is also considered a vapour barrier. Or, I could put in fiberglass batts with an even higher R-rating if I had 2" of cavity space.

But would the pipes still freeze?

The wall is double brick and it's not that cold in there even with the walls down. The walls don't feel freezing to the touch. They just feel cool. And I have patched up a lot of the holes in the masonry.

 
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02-27-09, 10:12 AM   #6  
Hi dz. The heat will always divide itself from inside temperature to outside temperature. So when there is nothing covering it, the surface will remain close to the inside temperature. Cover it with 2 inches of insulation and the reverse will happen, it will go to the outside temperature. Put sheetrock on one side and one inch of foam on the other with the double brick and it will be closer to inside than outside. But, air leakage, objects blocking the heat from the sheetrock, someone turning the heat down to save energy, power failure, and will it freeze??? There is a high risk.

And the issue with the brick may get even worse. I'm not up on brick construction at all, but have pasted a link that will talk about maintaining an air gap between your insulation and the brick. Now you upgraded your description to double brick, so I'm twice as "not qualified".

My thinking is the bulk of this problem belongs on the architecs desk. They get the big bucks AND they have project responsibility. What are they saying?

BSD-106: Understanding Vapor Barriers &mdash;

Bud

 
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02-27-09, 11:15 AM   #7  
Posted By: Bud9051
And the issue with the brick may get even worse. I'm not up on brick construction at all, but have pasted a link that will talk about maintaining an air gap between your insulation and the brick.

BSD-106: Understanding Vapor Barriers

Bud
The website in your link appears to be saying that the way most contractors and homeowners insulate is wrong. Also, all of the pictures of insulation being installed which I have ever seen are different from what is shown on the website.

The website seems to be saying that I am supposed to put up OSB. What is this OSB going to be attached to? Then the studs would be attached to the OSB I assume.

But before the OSB, there will be a vapour barrier and before that, there will be insulation, and before that, there is a 'drainage' channel. Then you have the bricks. What is this drainage channel? I can't have water pooling somewhere inside the walls because that would damage the bricks. I already have most of the bricks in the basement disintegrating because of moisture damage. There is nowhere for moisture to drain. There are no weeping tiles inside the walls, not even at the foundation, or a drainpipe or anything.

I was mostly looking at Figure 8 in your link because it looks like it matches my climate and house most closely. Except for one thing, the brick in this house is not a veneer, it is the structure. They didn't have plywood or OSB when this house was built. Maybe I should use Figure 15?

I will send your link to my architect and see if she has any advice. Now I can't decide what to do because I don't know enough and any decision I would make, even before I found your link, would be guessing, and probably wrong.

 
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02-28-09, 10:01 AM   #8  
Posted By: Bud9051 Hi dz. The heat will always divide itself from inside temperature to outside temperature. So when there is nothing covering it, the surface will remain close to the inside temperature. Cover it with 2 inches of insulation and the reverse will happen, it will go to the outside temperature. Put sheetrock on one side and one inch of foam on the other with the double brick and it will be closer to inside than outside. But, air leakage, objects blocking the heat from the sheetrock, someone turning the heat down to save energy, power failure, and will it freeze??? There is a high risk.

Bud
So I'm trying to research 'wet walls'. A wet wall would solve the problem of getting the pipes off the brick and further inside the building. If it covered the entire wall length, it would also enable me to put the pipes behind the sink and shower and toilet (not the toilet drain, just the intake pipe) so they could come out of the wall and not the floor outside the tiles. But it would create new problems in that I would have to build and insulate one wall, then build and insulate another one right in front of it to house all the pipes in that room. This would mean that the finished wall would end up being around 4" thick instead of the 1" it was before I demolished it. Also, based upon your explanation of how insulation works, it might not even protect the pipes from freezing. How will I know if the pipes won't freeze in a wet wall? This wet wall would also not have a heat source and it would be insulated to attempt to keep the pipes from freezing.

So what is the correct procedure for constructing a wet wall? My guess is you put up whatever insulation would fit against the interior side of the brick, then a vapour barrier, then sheetrock, then put up 2x4" studs for the wet wall, insulate between the studs, bring the pipes up through the bottom of the wet wall, another vapour barrier, sheetrock, then tile it.

 
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02-28-09, 10:53 AM   #9  
Has your architect seen the space after the walls have been stripped?

I'm not sure you have to classify this as a wet wall. I assume it is above grade?? Were there any signs of water/moisture damage before you removed the plaster? And I see no real indications of mold.

Is the ceiling below heated? Copper conducts heat very well, so if the space below is protected from the cold and has access to some heat, it may serve to protect your pipes with minimal insulation.

Problem is I'm guessing. You and the architect are the ones who will have to hash this out.

Wish I could help more,
Bud

 
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