# Will water lines freeze if placed behind insulated stud wall in basement?



## jpsmith (Jan 29, 2009)

Hello,

Perhaps someone knows the answer to this. I'm currently finishing my basement. The foundation along the front of the house is completely below grade, except for the last 12". In the back, the top 4' of the foundation is above grade. The water main comes in through the front wall and travels between joists to a tee along the back wall where it branches to feed the bathroom and kitchen above, along with the laundry room and hot water tank in the basement. The hot water line exiting the hot water tank parallels the cold water line to the bathroom and kitchen. Basically, the bulk of my water lines run along that back wall, just below the joists at or slightly below sill height.

With my basement fully open, no interior walls, and no heat, it maintains about 58-60 degrees throughout the winter, even through this very cold January we just had where the temperature was in the single digits nearly every night. There's no risk of my water lines freezing. However, I am worried that I am introducing a risk of them freezing if I finish the basement.

For insulation, I am gluing 1" extruded polystyrene boards the concrete block foundation. Then I am building my 2x4 stud walls about 1" from the blue board, then putting kraft-faced R-13 fiberglass batting between the studs. I have sealed all cracks and gaps along the sill to ensure that no air is penetrating. I am also insulating the band joist with R-13 fiberglass.

Along the wall with the water lines, I will frame the exterior walls about 3" from the block to allow room for the water lines and drains from above to run between the stud walls and the polystyrene board. Once these walls are up, the water lines will be isolated from the main basement area. Might they freeze if they're behind the stud walls, along this above-grade block wall with only 1" of blue board between them and the concrete blocks?

Thanks!


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## Ron6519 (Mar 28, 2007)

I would add pipe insulation to all the pipes and you should be fine. Sealing the rim joist and filling all the open areas you did was very important in keeping the cold temps from the pipes. The pipe insulation is added insurance.
Ron


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## Reilley (Sep 4, 2008)

Using Kraft Faced Batts will create an infamous "double vapour barrier"; the foam being the other. I suggest using unfaced batt insulation and spray foaming any voids in the foam insulation (where it meets the rim joist, floor, etc). So long as your plumbing is inside of the foam it won't freeze as the foam is acting as the vapour/moisture/thermal barrier. Check out this article for more information of basement insulation systems.

http://www.buildingscience.com/search?SearchableText=rr-0202


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## Wildie (Jul 23, 2008)

If you live where I live (Ontario, Canada) the answer is yes! They will freeze! No insulation should ever be between the heated area and water lines. Even if the walls have foam insulation!
In south, you'll likely be OK!


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## jpsmith (Jan 29, 2009)

Thanks for all the replies! I'd read that kraft-faced was OK to use and would not create a double barrier since the kraft-paper allows air/moisture to pass through. If that's not true, I have no problem using unfaced to avoid this. I'm trying to go out of my way to do this right, a large part of which is doing what I can to avoid mold.

Wildie - where in Ontario do you live? If it's Toronto or London, then your weather is somewhat similar to mine in Pittsburgh. If you live in, say, Thunder Bay, then no way. You're way colder.

Before starting the framing, I did make sure to seal up all air gaps in my blue board. I sprayed Great Stuff foam in any large gaps between the panels, taped all the joints with tyvek tape, and I sealed the perimeter - top, sides, and bottom with Great Stuff. I've tried to make sure that no air can get between the blue board and the concrete block.

If I Were to put the top plates of my walls a few inches below the water lines so that the lines sit in the area above the walls & ceiling and below the floor above, will this reduce the chance of the pipes freezing versus having them completely behind the insulated stud walls? I am going to use a low-profile drop ceiling and don't plan to use insulating panels because I don't care if heat escapes from the basement into the floor above.


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## Scuba_Dave (Jan 16, 2009)

My basement is unheated & stays at 55 or better
There isn't any insulation except around the rim joist
My basement is also underground except the top 12"
The ground below the frost/freeze point stays at 50-55
I would have no problem installing water pipes about 1/2 way up the wall behind the insulation - provided they have pipe insulation on them

What water lines are you running?
Drop ceiling or wallboard?


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## jpsmith (Jan 29, 2009)

The attached waterlines.jpg shows my 1/2" water lines along the wall I'm talking about. As you can see, the hot line is already insulated. I did that recently just to conserve energy and have hotter water faster at the taps & shower. It helps. I had to lower the thermostat setting on my hot water tank.

The top three and a half blocks in this wall are above grade. The frost line here is 36" below grade. If I were to place these water lines lower than that, they'd be right down around floor level. I _could_ do that, I guess, but I really don't want to move the water lines... again. You can see in the picture that the copper is new. I just replaced the original 60 year old lines a few weeks ago. They were corroded at the connections and the previous owner had done some bending of the lines instead of using ells, and they weren't soft copper - they had kinks in them!

Having the walls not go all the way to the joists but rather stop a few inches below the water lines wouldn't be a problem for me, because you can sort of see that I'll need to put the ceiling below the valves, the large copper drain line (top center) and the duct work (top right). It will be a drop ceiling. For most of the finished area it will be right up against the joists, using something like a ceiling link system (http://www.ceilinglink.com/). In the area of concern here, the ceiling will be dropped about 7" to account for the obstacles - duct work, drain pipes, and the water valves you can see in the picture.


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## Wildie (Jul 23, 2008)

jpsmith said:


> Wildie - where in Ontario do you live? If it's Toronto or London, then your weather is somewhat similar to mine in Pittsburgh. If you live in, say, Thunder Bay, then no way. You're way colder.
> 
> .


 I'm about a 1/2 drive from Pt.Huron MI.
The thing to remember is that insulation retards the flow of heat, but it does not stop it! For instance, our homes require a continuous supply of heat to replace what is lost through the insulation! If heat is prevented from reaching your plumbing, its latent heat will eventually bleed away and when it reaches 32F it freezes.
Warmth from your home must be allowed contact the plumbing, and to replace heat lost through the insulation.
Pipe wrap only works for awhile, and if water flow doesn't replace the cold water, the pipes will eventually freeze.
Pipe wrap will delay freezing, but not prevent it!


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## Scuba_Dave (Jan 16, 2009)

My last house had a crawlspace that was unheated
In addition the floor to the house was insulated
So no heat going to the crawlspace (or very little)
The pipes never froze in the 7 years I lived there


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## Reilley (Sep 4, 2008)

Being that your basement is nearly completely below grade I doubt you would have freezing issues if the water lines were lower. The part of my basement (cellar, cold zone) which completely-submerged has not dropped below 2C, even during a week or two stretch of -20 to -30 degree Celcius weather. I record the temperature at the outside corner of the walls. 

What worries me is that the pipes are very close to the rim joist, which is going to be the coldest spot on that wall.

Keeping it within the foam vapour barrier will prevent them from freezing so long as you insulate your basement header well (cut / seal pieces of foam in each joist bed). Otherwise, you could move your plumbing a bit.

Oh, and as far as I am aware, Kraft Paper is a vapour barrier.


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## Ron6519 (Mar 28, 2007)

I'd replace those shutoffs with ball valves before starting the framing.
Ron


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## jpsmith (Jan 29, 2009)

Ron6519 said:


> I'd replace those shutoffs with ball valves before starting the framing.
> Ron


Why? Is there any benefit apart from being able to open/close the valve more easily?


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## AllanJ (Nov 24, 2007)

I would omit or cut away insulation "in front of" the pipe while putting insulation as good as possible "behind" the pipe and lining the exterior wall. A suggested insulation free zone might be a triangular section of empty space following the pipe and about as wide at the wall surface as it is deep..

In the picture, you could put 10 inches of insulation up in the joists out to the band joist (rim joist)except less where a pipe sticks up through the edge of the subfloor into an exterior stud wall above. This batt insulation would stick in past the sill plate a few inches in most areas. No wall insulation would cover the pipe where it is attached to the sill plate.


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## joed (Mar 13, 2005)

No insulation between the pipe and heated area. You need to let heat get to the pipes not insulate them from the heat.


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## jpsmith (Jan 29, 2009)

Thanks again to everyone that's helping and offering suggestions. I've made a rudimentary mock-up, seen below. Would the system I've drawn up here allow enough warm air from inside to reach the pipes while keeping enough cold from outside from getting to the pipes to ensure they won't freeze? What I've drawn gives an R23 value to the rim joist area and R10 between the pipes and the concrete block. This should slow heat loss through the foundation wall and rim joist considerably, but will this setup allow enough heat to reach that space so that the temperature there never drops below freezing?


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## jpsmith (Jan 29, 2009)

Ron6519 said:


> I'd replace those shutoffs with ball valves before starting the framing.
> Ron





jpsmith said:


> Why? Is there any benefit apart from being able to open/close the valve more easily?


I'm following up to this in case anyone finds this thread in a search somewhere down the road and wonders, like I did, why ball valves are recommended over shutoffs. The answer I found, in short, is that ball valves are less likely to leak.

http://www.rd.com/advice-and-know-how/51360/article51360.html


Regarding kraft-faced insulation, I dug a little deeper and have discovered that the kraft paper serves as a vapor barrier but not an air barrier. Therefore, if I were to use it in my stud walls after having glued XPS to the foundation walls, I would be creating a double vapor barrier and bad things would happen.

Does anyone care to comment on the mockup I posted in comment #15? Any thoughts on if this setup will allow the water lines to receive enough heat during the coldest days?


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## Wildie (Jul 23, 2008)

jpsmith said:


> I'm following up to this in case anyone finds this thread in a search somewhere down the road and wonders, like I did, why ball valves are recommended over shutoffs. The answer I found, in short, is that ball valves are less likely to leak.
> 
> http://www.rd.com/advice-and-know-how/51360/article51360.html
> 
> ...


 My son had a similar situation to yours! His ceiling was a dropped T-bar ceiling! As the air space above was dead air with no flow, his pipes froze!
He used sections of 'egg crate tile' to allow air flow! This resolved his problem!
Somehow, you should allow some ventilation into the ceiling space!


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## Ron6519 (Mar 28, 2007)

jpsmith said:


> Why? Is there any benefit apart from being able to open/close the valve more easily?


The washers need to be changed on these valves. The packing around the shaft leaks over time. The valves frreeze in the open position when they're not open and closed, especially if they're locked in the open position. They project down much further than a ball valve.
Ron


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## Winchester (Aug 27, 2008)

When I get around to finishing my basement, I'm going to use 2" foamboard (R-10) with furring strips over the top to create my exterior wall. Is this a possible scenario in your situation? This would give you increased R-value from the outside and less insulative properties from the inside (drywall only I presume). The heat from the basement will be more readily available from the inside to prevent freezing of these pipes that are "sandwiched" in the wall cavity.

As a side note, are you going to insulate the floor as well and create a subfloor? You may want to consider this if you're truely interested in insulating your basement. I've seen the use of 1" high density foamboard and 1/2" or 5/8" flooring used in this situation. Or there are the Dricore or OvrX (?) systems.

Best of luck.


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## jpsmith (Jan 29, 2009)

Wildie, I think the egg crate ceiling tiles is a good idea. I could put them in the last row along that wall and if I paint the joists and subfloor above white, it won't look to bad I don't think. Plus, this area is just going to be a half-bath and a fruit cellar, so seeing through the ceiling tiles won't be the end of the world.

Thanks, Ron. I wish I'd have known that ball valves were better a month ago when I was putting in those lines...

Winchester, it's a good suggestion, but I'm not keen on using furring strips for my walls for a couple of reasons. First, my block foundation walls aren't perfectly straight; they have a bit of a bow to them. If I used furring strips, that bow would transfer to the finished wall. By framing in with 2x4 stud walls, I'm guaranteeing that my walls will be straight, plumb, and square. Also, I plan to fully wire the area with plenty of receptacles and light switches, and having stud walls makes this easy. Finally, the area I'm concerned with in this thread is going to be a half-bath. It already has a toilet drain set in the floor. I just have to add water sources for the commode and lav, and add a drain for the lav. I'd have no place to put these things if I used furring strips.

In case anyone's interested, attached is a PDF that shows the layout I'm going with. Unfortunately, the grid from visio didn't transfer to the PDF when I printed to file, so you can't see measurements in this drawing. It's 41' by 26' total.


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## jpsmith (Jan 29, 2009)

Winchester said:


> As a side note, are you going to insulate the floor as well and create a subfloor? You may want to consider this if you're truely interested in insulating your basement. I've seen the use of 1" high density foamboard and 1/2" or 5/8" flooring used in this situation. Or there are the Dricore or OvrX (?) systems.


Sorry, I didn't answer this question when I answered others... I'm seriously considering using Dricore with engineerd hardwood on top of it for the main living space, then for the half-bath and mud room, I plan to put tile on hardibacker. The Dricore is 7/8" thick, and the hardwood ranges from 1/4" to 3/4". This means where the tile meets the hardwood, the hardwood will be a bit elevated. Now I'm wondering if I could put 1/2" foam board underneath the hardibacker. Off to research...


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## jpsmith (Jan 29, 2009)

What I decided to do was:

1. Move the water lines away from the wall about 6". 

1a. While I was soldering, I replaced the shutoffs with ball valves and roughed in for the toilet & lav. It worked out well. Ironically, the ball valves leaked after one week. But I just had to tighten the nut behind the handle one each one. Apparently the factory didn't tighten them.

2. Install 4" of blue XPS up against the wall in the same manner I installed 1" of it along all the other walls. I used 4' x 8' x 2" boards, two layers thick. I taped and sealed the first layer before applying the second layer, which I also taped & sealed. This gives me an air-tight R20, with the water lines on the warm side.

3. Frame up the stud wall and install no fiberglass in this wall. This will allow heat to go through the drywall and keep the waterlines from freezing. But the heat won't escape beyond the blue board that's between the water lines and the foundation wall.


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## jpsmith (Jan 29, 2009)

jpsmith said:


> ...then for the half-bath and mud room, I plan to put tile on hardibacker. The Dricore is 7/8" thick, and the hardwood ranges from 1/4" to 3/4". This means where the tile meets the hardwood, the hardwood will be a bit elevated. Now I'm wondering if I could put 1/2" foam board underneath the hardibacker. Off to research...


I should post back here with the results of my research. Yeah, that was a bad idea. You can't put backer board on top of a concrete slab. I'm going to be doing a 1.5" mud job in my bathroom and mud room, so with the 1/4" tiles it will bring that floor about level with the dricore/floating floor in the rest of the basement. I might need a transition piece, but it won't be dramatic.


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