Easiest way to insulate frozen pipes on exterior wall?

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miketp

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During a bathroom renovation, plumber convinced me to move the shower/tub faucet to the opposite wall so it was easier to reach. Unfortunately the opposite wall is an exterior wall and the pipe now freezes. No issues with the sink/toilet on the other (interior) wall. Pipes are not wrapped in any insulation (even though I would've thought at minimum the hot pipe should be wrapped) and plumber says the freezing is the carpenter's issue for not adding insulation.

Besides letting the tub faucet drip when it's cold, what's the easiest way to remedy? Some options I can think of:

1) Remove trims and spray expanding foam insulation in the holes (great stuff?), but I think this would encase the entire pipe and make repairs more difficult and prevent interior heat from reaching the pipes

2) Remove trims and spray non-expanding foam insulation in the holes toward the outside wall only. Is there a specific brand/type of foam that should be used, would a few cans be enough, and could I cover enough to insulate using just the shower and trim holes?

3) Remove tiles, break the wall, and put in fiberglass insulation
 

Cacher_Chick

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You want the interior side exposed to the heat of the room. It helps to run the piping as close to the interior wall as possible, so the maximum amount of insulation can be applied behind it. The foam is better than fiberglass, but you need to get that entire stud bay insulated behind the piping or you will not have accomplished much.
 

WorthFlorida

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Do you know where it is freezing? In the wall between the studs or between floors such as first to second floor? No amount of insulation will help unless there is a heat source. The exterior wall should have been double stud in thickness to get at least 3.5 inches of insulation behind it and then the pipe would have a warm side (heat from the home). If you think it is freezing between floors you need to get heat in the joist area. On the lower level you cut a hole in the ceiling and place a slotted vent and cover the hole to get heat in that cavity. Since you're in the deep freeze this is just to get you buy so a permanent solution can be had when the cold easy up above freezing for a while.

Since you are going to get another blast of cold, can you turn off the water to these pipes from another area? If you can turn off the water and try to drain the pipes by opening a faucet and let the water drain out from a lower level. You'll have to live a day or so without the use of this bathroom but it is far better than having a blown pipe dumping water at 3:00 AM.

I think you got a bone headed plumber for the job and made changes to make his job easier. All depending how the pipes were run, he should have informed the carpenter about the change. Was there a inspection? A inspector should have noticed this.
 
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miketp

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I would imagine the pipes in the wall between the studs are freezing, but how can I verify? The kitchen is directly below (so cutting a hole in the ceiling is unlikely) and those pipes never freeze, and the washing machine in the room above also doesn't freeze. The pipes only freeze a few times a year when it gets really cold. They unfroze last night and I'll let it drip when it's cold until we have a permanent solution.

Plumber put in new pipes in the entire house, this is the only one with issues. He actually charged more to route the pipes this way, and it definitely made the job a little harder. Inspector didn't mention any issues.
 

Jadnashua

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Any siding, rim joist, or other area of air leaks into the stud cavity will make regular fiberglass operate just like a nice furnace air filter (IOW, any insulation only works if you don't have air moving through it - it must be trapped)...you need to stop any air infiltration AND trap some heat, which means insulation behind the pipe to the wall as has already been said. IF you used spray foam, unless you could accurately direct where it was applied, could end up insulating the pipes from the heat in the room and make things worse. Depending on exactly how deep into the wall the pipes are, you may not be able to get enough insulation behind them to prevent this, but if there are air currents in the wall, you have to stop them first.
 

Sluggo

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Even if it only freezes "a few times a year," this is a flood waiting to happen. I have to say it, but I would break into the wall cavity, and insulate with fiberglass between the pipes and the outside; I would leave the pipes exposed to the interior side to pick up room heat. I would also make sure that any penetrations are sealed. I recently had my first freeze in a kitchen in the ten years I have been in this house with a kitchen sink that had pipes in an insulated, exterior wall. When I cut into the sheetrock under the sink I found a penetration hole in the bottom plate that allowed a nice cold breeze into the wall from outside, and it froze the pipes even though there was insulation between them and the outside wall. Once I blocked that, no more problems. If I had your situation, I would choose to get at the wall cavity from the outside: although this would be a pain, it would seem to be less of a pain than tearing out your tile work.
 

Jadnashua

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The biggest advantage to fiberglass insulation is it is cheap and easy to install...it is by far not the best in performance. It is almost totally transparent to an air leak. Insulation relies on trapping air - movement can overwhelm it by removing any of the heat that might have been trapped. As said, you really must keep the pipes open to the warm side, but add as much insulation as you can towards the cold side. That often requires foam, and closed cell foam is more efficient than open cell stuff whether in a sheet or spray in. YOu must block off any air leaks, or the amount of insulation is almost irrelevant.
 
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