Experiencing frozen indoor PEX lines -- but only on cold and not hot?

[PorkChopsMmm]

Hey guys -- quick question from a frustrated cabin owner. We built our place ~2 years ago and this is our first winter here. Below is a diagram of our first floor. We have the water entrance in the back corner of the kitchen. From there I have a hot and a cold going directly to the kitchen sinks. I also have a set of hot and cold PEX lines going directly to the bathroom area.

I am experiencing freezing at random -- it is cold enough to freeze outside but all of the PEX piping is within our insulated interior. The lines are run in the ceiling of the first floor (we have a 1.5 story cabin) next to an exterior wall and/or knee wall of the ceiling that is insulated. Last night has been our coldest night here in Michigan (sub zero) and my cold water line froze. Not the hot water -- just cold water. They run right next to each other throughout the run from the back corner of the kitchen to the bathroom. During the rough-in of the interior I put black pipe insulation (low R value) to try and keep the hot water hot as it ran through the house.

Last night I had a slow trickle on both the hot and cold water lines and when I woke up the cold was frozen. It is still frozen now even with a propane heater going in our bathroom and bedroom. This is not the first time the line has frozen but usually it "thaws out" after we get the temperature back up to ~70 degrees from ~60 degrees when we wake up.

Any hints or tricks? The ceiling on our first floor is finished and I don't want to rip it up if I don't have to. I have gone around the exterior wall and ceiling with a laser temperature gun and see no significant variances in temperature. From our pantry in the picture I have slight access to the inside of the ceiling of the 1st  floor and I can detect no temperature variances there either.

I am left thinking that maybe a crack in the siding our some such is allowing cold air in? But wouldn't I see a temperature difference on the wall/ceiling area? I actually have no idea where this is freezing -- just that any bathroom faucets downstream from the kitchen don't have any cold water. The hot and cold runs from the kitchen area to the bathroom are all one long run of PEX without any joints for leaking -- and so far I haven't see/heard/etc. any signs of leakage. Sorry for the rambling -- I have been battling cold related issues all day.

Anyone with some "been there done that" tips?
Thank you!

[Redoverfarm]

What is the situation with the lines running adjacent to the exterior walls? Were the lines in place when you later insulated? Did you situated them in mid-center of the cavity?  Is there insulation between the pipe and the exterior wall?  Generally lines run within the residence will not freeze if there is sufficent heat.  Problem arise when they are in unheated crawlspace ,lying against the exterior sheet, or in unheated attic.

[PorkChopsMmm]

I am not the most experienced builder so I will try to describe this correctly.

For the horizontal run you see in the picture the hot and cold lines are in the "kneewall" area of the second floor. The outside wall of this kneewall is the roof and is definitely insulated.For the run of the lines down to the bathroom the lines are mounted to the top plate? It is the beam that separates the first and second floor. So the first floor wall is insulated and so is the second floor but the "beam" is not -- it's just a wood beam.

Here is a picture (not mine) that kind of illustrates it -- the beam between the two floors. So it is covered with the wall exterior wall sheathing and the tyvek.


I used the temperature gun to monitor the interior wall and ceiling temperatures and I also went outside to see if I could see any warm spots. No dice on either test.

[MountainDon]

The temp meter reads the surface temperature. I'm not certain that the "everyday" variety can discern a spot where it may be colder inside, under the surface. The folks who do the thermal scans to find deficiencies in insulation have much more sensitive equipment, I believe.

Nor sure what to suggest as a cure for the moment. 

Too bad it is not all copper... hooking a welder to it for a little resistance heating can work. Then again, if it was copper maybe you would have running water right now. Running down the wall as in a leaking, cracked pipe. 

[PorkChopsMmm]

Don, I think you are right if the piping was copper. I didn't think my cheap temperature gun would do that well but I figured if the inside temp is 70 degrees and the air leak, or whatever it is, is enough to freeze an indoors what pipe that the surface in the general area of the frozen pipe would have a different temperature.

[PorkChopsMmm]

BTW the cold water pipe thawed out last night -- with no effort from myself... and it was just as cold outside. I left a trickle from the faucet and when I woke up this morning the line was frozen again. 

I am going to cut into our tongue and groove ceilings in our bedroom and see if I can figure out what is going on.

[UK4X4]

I was discussing pipe freezing with my soon to be plumber last week in CO

I don't have a between floors space as I'm using 2x6 and beams

we intend to do base boards set off from the wall an inch or so ie boxed inside the house

but he also wants to add ventilation vents from inside the house- ie the air in the duct will be the same as the room
rather than shut off from the inside heat.

he also wants to run the heating pex in the same places

If you know the route may be just adds some vent holes where the pipes run, rather than rip the whole lot out straight away

I guess you just have some conduction from outside somewhere- small draught

[Redoverfarm]

BTW the cold water pipe thawed out last night -- with no effort from myself... and it was just as cold outside. I left a trickle from the faucet and when I woke up this morning the line was frozen again. 

I am going to cut into our tongue and groove ceilings in our bedroom and see if I can figure out what is going on.

  Ouch!

[MountainDon]

but he also wants to add ventilation vents from inside the house- ie the air in the duct will be the same as the room
rather than shut off from the inside heat.

Running a "chase" lengthwise down the house, not near the exterior walls, is something I've seen done here. Our PB repipe to PEX was done like that. It is extremely well insulated and has vents in several places. THis was added in the attic space above the one story ceiling.

[Ndrmyr]

It might help to have someone with a good Infrared Carmera come and look for hotspots (outside) and coldspots (inside).  The challenge is that if your pex is running in a cold area, it might be inacessable from the inside and show no warmth from the outside.   Most good home inspectors have Thermal Cameras and might give you a hand for a couple of bucks. Worth a shot.
For that line to be freezing when the water is running in weather that isn't severely frigid, implies that somewhere it is seriously exposed to cold.  It doesn't take much of an omission for cold to penetrate.  Worse case, I would start wondering if there is a way to run replacement PEX, a small curb at the floor of the upstars or whatever.  It might be cheaper to tie off the old lines and tap in new ones than try to fix the existing problem.

[PorkChopsMmm]

All good ideas guys -- thank you.

I do have *some* access to this space via an upstairs room. Just enough to shine a flashlight, hold a mirror, etc. I found out that the duct from my bathroom vent light came unhooked and some cool air was coming into the space but it wasn't nearly enough to freeze the pipes. I think I can cut out a small section of tongue and groove in our bedroom ceiling to expose the pipes. I think I can replace the T&G without much ado. If it requires anything more intensive then I will consider other options.

[NM_Shooter]

Well, the good news is that it is Pex, and freezing does not seem to hurt it... nor does it break the brass joints. 

The bad news is that you only need a little spot of the pex to have just a little less insulation on it for that spot to freeze and plug the line. 

I'm guessing that you have one small portion of your run that is freezing on you.  Trying to find that spot will be tough.  I don't think there is an easy fix for this. 

[CjAl]

my guess is because you have it mounted right to the top of that beam. the insulation comes down and ends right on top of it. you probably have cold air coming around the end. shouldnt it be run through the studs higher up with insulation split around it half in front half behind the pipe to keep it warm? mabey open it up and have it spray foamed?