Blowing heat up an exterior wall to keep water line from freezing

[Don_Edm]

Good day all.
I've been to this site a lot and value everyone's replies.
I'm hoping someone may have a thought on if this would work or not.

We have a 2 story walk-out and this Winter we've had a single water line freeze in a bathroom on the top floor.
The water lines to this bathroom go up an outer wall and and the builder used foam insulation between the outside and the water lines (they say according to code). We can't really see where the line is freezing because we haven't torn apart the wall yet.
At the top floor the one line that freezes does make a turn at the floor height and goes about 5 feet and then up to a sink.

The builder came out to take a look and their final solution to stop the freezing is to branch a heating duct in the unfinished basement over to the wall below the sink 2 stories up. Not actually running duct work up the whole wall to the 2nd story, but just to the wall and into where the insulation is and direct it up.
They say the heat will flow up the inside of the wall and keep the water line from freezing.

I can't say that I'm a fan of this solution and can't seem to find anyone who has a good answer as to if this is a good idea.
My concerns are that the heat would never actually get to the top floor where the line freezes. And they don't know if the line is freezing in the wall where it runs up, or where it runs along the floor and up to the sink. They want to run the heat up to where the line is running along the floor.
I say running along the floor, but I don't know exactly how it is run, if it's up against the wall, or in the wall at that point.
My other concern, is that blowing heat into the wall all winter would introduce a lot of humidity in the wall and can cause mold issues after a period of time.

Any other thoughts/opinions on this?

Thanks so much.
Don.

 

[Dana]

Blowing humid conditioned air though 10 feet of fiber insulation inside a stud isn't going to provide much flow due to high flow resitance of the insulation but it will be inserting copious amounts of humid air into that stud bay, much of which will accumulate in the exterior sheathing of the house creating a potential mold & rot situtation in spring when the sheathing warms up to consistent mold-growth tempertures.

The dew point of conditioned air in winter will normally be about 3-4C, even higher if humidity is being actively added (almost always a bad idea.) What do you figure the average wintertime temperture of the sheathing is in Edmonton? (I'm guessing -10C, maybe colder, and WAY below the dew point of the air being injected into the stud bay.) Though the hot air will be heating the sheathing near where the air is being inserted, it won't be raising the temperature of the sheathing higher up in the bay by very much, but the vapor permeability of the insulation is high- the moisture will travel much further than the heat will, since the insulation resists heat flow, but not moisture flow.

 

[Sponsor]

 

[Don_Edm]

I don't think there would be a moisture problem, though I also don't see how he would blow air up a wall either. I'm glad he's not thinking of an air duct, as they really don't offer insulation when the heat is off.

Thanks for the reply!
Yes, I can't see how the air is going to get up through the wall being that it's all insulated.
Thanks again. Much appreciated.

 

[Don_Edm]

Blowing humid conditioned air though 10 feet of fiber insulation inside a stud isn't going to provide much flow due to high flow resitance of the insulation but it will be inserting copious amounts of humid air into that stud bay, much of which will accumulate in the exterior sheathing of the house creating a potential mold & rot situtation in spring when the sheathing warms up to consistent mold-growth tempertures.

The dew point of conditioned air in winter will normally be about 3-4C, even higher if humidity is being actively added (almost always a bad idea.) What do you figure the average wintertime temperture of the sheathing is in Edmonton? (I'm guessing -10C, maybe colder, and WAY below the dew point of the air being injected into the stud bay.) Though the hot air will be heating the sheathing near where the air is being inserted, it won't be raising the temperature of the sheathing higher up in the bay by very much, but the vapor permeability of the insulation is high- the moisture will travel much further than the heat will, since the insulation resists heat flow, but not moisture flow.

Thanks for the reply!
I've been online reading on this for quite some time and it was tough to really find information on this type of a situation. You've explained it very clearly. Thank you so much!
This year we had a solid couple of weeks of around -35 to -40, not including wind chill... those days were the times the line froze. But the average is probably -10 to -20. The next 2 nights we're expecting about -30 (ish), but then we will be warming up.

I'm going to talk to our builder and just say NO to their plan.
I didn't feel comfortable with their solution before, and this really solidifies my concerns.

I think going from the outside, adding more insulation, and putting it all back together again in the right plan.

Thanks again for your thoughts on this!!

 

[WorthFlorida]

With a two story house and pipes freeze it is generally in the joist area, that is between the ceiling below and the floor above. When the pipe froze and thawed there were no leaks? Your lucky. If you’re going get hit with another deep freeze, I would cut a hole in the ceiling near the wall to allow warm air to raise into the floor joist. Cover the hole with a return grill for appearance but it is by no means a fix but better than frozen pipes.

How thick are the outside walls, 2x4 or 2x6? Do you know how close the pipes are to the the warm side of the wall? Are the pipe CPVC? Is it all foam insulation? Adding insulation is only beneficial if there is a heat source to keep the pipes warm.
Generally, all pipes in a cold climate should run up to the second floor on an interior wall, then run along the floor joist and come up under the bathroom cabinet so it is well away from the exterior wall cavity. The pipe should not go through the top wall plate on exterior walls. This only good practice.

 

[Don_Edm]

With a two story house and pipes freeze it is generally in the joist area, that is between the ceiling below and the floor above. When the pipe froze and thawed there were no leaks? Your lucky. If you’re going get hit with another deep freeze, I would cut a hole in the ceiling near the wall to allow warm air to raise into the floor joist. Cover the hole with a return grill for appearance but it is by no means a fix but better than frozen pipes.

How thick are the outside walls, 2x4 or 2x6? Do you know how close the pipes are to the the warm side of the wall? Are the pipe CPVC? Is it all foam insulation? Adding insulation is only beneficial if there is a heat source to keep the pipes warm.
Generally, all pipes in a cold climate should run up to the second floor on an interior wall, then run along the floor joist and come up under the bathroom cabinet so it is well away from the exterior wall cavity. The pipe should not go through the top wall plate on exterior walls. This only good practice.

Good day!

They are pex lines. No leaks yet.
The walls are 2x6 and the insulation up that wall is spray foam. Unfortunately we haven't opened it up to get a look at it yet. The exterior wall in this case was the choice the builder made (or plumber made) due to the layout (open concept). The plumber kept saying "it's to code" and "passed inspection" and that it's fine... but it's freezing, so the builder will have to do something. He said it was closer to the inside, but I really won't know until we open it up and check.

Along with adding insulation, we think we're going to use a recirculating pump to the hot water line at that sink and have the return on the cold line that we had issues with. So that will at least have some warm water in it when it gets really cold again.

When they remove the outer wall to check/add insulation I'll make sure I'll check to see if they did go through the top wall plate.

Thanks for your reply. That's great information!
Don.

 

[WorthFlorida]

I only mentioned the top plate so the pipes can be further from the exterior wall but many do go through it. If the pipe must go up the wall it can only go through the top plate, otherwise you’ll need a soffit and it’s then not pretty. With PEX it is pretty forgiving but it’s the connectors and angles made of metal or plastic that can crack with freezing.

 

[Don_Edm]

I only mentioned the top plate so the pipes can be further from the exterior wall but many do go through it. If the pipe must go up the wall it can only go through the top plate, otherwise you’ll need a soffit and it’s then not pretty. With a PEX is pretty forgiving but it’s the connectors and angles made of metal or plastic that can crack with freezing.

That's a great point! The builder kept saying that it's PEX and to not worry about it freezing... but if there were any joins in there (which there shouldn't be), then those could easily crack with freezing.
Thanks so much for that. Something like that is easily missed!

 

[Jadnashua]

If the pipes are run along the inner wall versus being embedded in it, the heat from the home doesn't get to them as well as it should.

 

[sarvesperi]

Thanks for the reply!
I've been online reading on this for quite some time and it was tough to really find information on this type of a situation. You've explained it very clearly. Thank you so much!
This year we had a solid couple of weeks of around -35 to -40, not including wind chill... those days were the times the line froze. But the average is probably -10 to -20. The next 2 nights we're expecting about -30 (ish), but then we will be warming up.

I'm going to talk to our builder and just say NO to their plan.
I didn't feel comfortable with their solution before, and this really solidifies my concerns.

I think going from the outside, adding more insulation, and putting it all back together again in the right plan.

Thanks again for your thoughts on this!!

Having same problem. Upstairs master bathroom shower is exposed to outer wall. When temperatures fall below 15 or so, there is some leak that shows up as water mark on downstairs room ceiling. Several attempts from various contractors did not yield resolution. It goes away once temperatures are normal.

Did you resole your issue? What was the solution, it may help me as well