Heat Tape Through Joists

[kgordon]

Hey everyone,
I think i know the answer to this but wanted to get some other opinions. Last year i had a plumber run pex lines in a crawl space for a new half bath in what used to be a porch that was enclosed years ago. This is not a heated crawl space. The plumber ran the pex through the joists to keep it as high as possible and used foam insulation. I then added fiberglass over the top in the joist bays and even boxed it in with foam board. Needless to say it froze twice last year.

So i wanted to add heat cable to it but he drilled 3/4" holes for a 1/2" line. So my thought was that i just need to rerun the pex, pull it below the joists so i can run heat cable on it. I don't want to try and cut a larger hole with the pex in there. Though i suppose i could remove the pex, cut out a larger hole and then reinstall in the joists.

Thoughts?

 

[Kaizen]

Yup pull it out and strip it of insulation. Put on the heat tape but not sure if there is a different one for pex? I have some on pex and it turns to spaghetti. Anyway use rubber insulation...not cheap foam. Make sure you get every inch of it. Might be able to just plug in heat strip when you know it's going to freeze for days. Might want to put the whole thing inside a larger pvc to make hanging easier. Just hang under the joists


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[kbs2244]

You have insulation between the floor and the pipe?
If so, it is in the wrong place.

You want to shield the pipe from the cold.
The cold is below the pipe.

Remove ant insulation between the floor and the pipes to allow heat to come down fro, above.
It will not be much heat but with insulation below the pipes it should be enough to prevent freezing.

Your heat tape idea will work.
Just be sure it is temp controlled with the sensor in the pipe cavity.

 

[T_R]

Just drill another small hole in each joist next to the existing one and run your heat tape. It doesn't need 100% contact to work.

Take the insulation above the pipes off, you want the floor heat to migrate down to the pipes to keep them warm.

Also leave the water running when it's really cold at night. A small stream just above a drip and it won't freeze.

 

[Bert_]

You have insulation between the floor and the pipe?
If so, it is in the wrong place.

You want to shield the pipe from the cold.
The cold is below the pipe.

Remove ant insulation between the floor and the pipes to allow heat to come down fro, above.
It will not be much heat but with insulation below the pipes it should be enough to prevent freezing.

Your heat tape idea will work.
Just be sure it is temp controlled with the sensor in the pipe cavity.

This^

Insulate below the pipe. No insulation between the pipe and the floor.

 

[ItsNemo]

And throw a vapor barrier under all of that to keep the breeze out...air movement through insulation will still cause it to freeze.

 

[kgordon]

Thanks all. I wanted to avoid leaving the faucet dripping, thats the whole point of removing all this. I think pulling out the lines, running under the joists with heat tape and fiberglass wrapped insulation will be the answer.

 

[n20junkie]

You shouldn't have to heat tape if properly installed. It is a system that you rely on, and when it fails, your going to have issues again.

If you only insulate the bottom of the pipe, and keep the arflow to a minimum, the pipe will easily keep warm from the floor heat radiating down.

 

[kgordon]

You shouldn't have to heat tape if properly installed. It is a system that you rely on, and when it fails, your going to have issues again.

If you only insulate the bottom of the pipe, and keep the arflow to a minimum, the pipe will easily keep warm from the floor heat radiating down.

This is a small room and in the winter we usually keep the door closed to the bathroom and office as its off the living room and lets cold air in. Whoever built this thing did a "quality" job.

I'm confident that there is not enough heat coming from above to keep the lines from freezing. I had issues last year when we had 3 or more days of below 0 temps.
The heat tape has a thermostat and the plug lights up when its working so i should know when it fails. I am in the basement every day so i will notice if they go out.

Thanks for the input.

 

[samss]

Get a self regulating heat trace like Raychem W51-24. It'll only heat where and when needed, can be overlapped and cut to length.

 

[gungatim]

I would have had the plumber use a recirculating pump on that circuit. hindsight.

 

[Bert_]

I'm confident that there is not enough heat coming from above to keep the lines from freezing. I had issues last year when we had 3 or more days of below 0 temps.

There isn't any heat coming from above because you insulated between the floor and the pipe! Your insulation is preventing the heat from getting to the pipe...

The insulation belongs below the pipe with none above it.

 

[Angelfire]

I'd also consider insulating that crawl space.