Ok to route radiant PEX under joist instead of through?

watercourse

I'm wondering if you could offer some advice?

I'm installing PEX in joist bays above a crawlspace.

I'm struggling to feed the PEX back and forth between joist bays because it's binding in the 2" holes I drilled, so I wonder if I can instead just cross under the joists to get between the bays, and maybe put a bit of pipe insulation over the small section of PEX that would pop out below the joist.

EBEBRATT-Ed

Shouldn't be an issue

ethicalpaul

I'll be curious to see what the pros say, but I can't see why not...but how is 1/2" (presumably) Pex binding in a 2" hole?

Also, is the crawlspace conditioned? Or open to the freezing outdoors?

watercourse

ethicalpaul said:

I'll be curious to see what the pros say, but I can't see why not...but how is 1/2" (presumably) Pex binding in a 2" hole?

Also, is the crawlspace conditioned? Or open to the freezing outdoors?

It really starts binding after it's gone through 2+ bays. I guess the little bit of drag from each hole adds up. And I tried pulling the whole pipe length through each bay, but it gets really twisty. So going under the joist seems a lot easier. I guess just held in place with a pex talon or something and covered in some foam rubber pipe insulation?

The crawlspace isn't conditioned. I'll be insulating the bays.

ethicalpaul

Ahh well you can't just pull it through multiple bays, you have to push it through one bay at a time, with the correct single "twist" in it so that it ends up in the right pattern.

It will be a lot easier to insulate it well if it's all in the bays and not coming underneath each one.

ethicalpaul

See my pics here. I'm a DIYer too. In a crawlspace is not nearly as fun I'm sure:

https://forum.heatinghelp.com/discussion/183827/recommended-floor-condition-for-radiant-over-heart-pine-plank

Jamie Hall

I hope those holes were less than a third of the depth of the joist, and located on the midline of the joist... otherwise you have created a serious structural issue there.

yellowdog

for insulating purposes, it will be a lot easier if your pipe isnt running below the joist to get to the next bay.

watercourse

yellowdog said:

for insulating purposes, it will be a lot easier if your pipe isnt running below the joist to get to the next bay.

Yeah that appears to be the tradeoff for me right now. Easier to install the pex vs easier to insulate the pex.

watercourse

Jamie Hall said:

I hope those holes were less than a third of the depth of the joist, and located on the midline of the joist... otherwise you have created a serious structural issue there.

Yes

watercourse

ethicalpaul said:

Ahh well you can't just pull it through multiple bays, you have to push it through one bay at a time, with the correct single "twist" in it so that it ends up in the right pattern.

It will be a lot easier to insulate it well if it's all in the bays and not coming underneath each one.

How do you do the correct single twist?

I was wondering if it was possible to keep the pipe somehow organized or coiled back up at the end of each bay as you pull through.

mattmia2

You might want to get some unsplit insulation and slip pieces of it over the tube as you are installing it.

Mad Dog_2

You really need two people on those radiant staple up crawl space jobs. One to feed the pex and keep turning to stop kinks and one to fasten to the plates.  Technically you're cheating by crossing under the joists but you gotta do what you gotta do.  It's not the end of the world. Mad Dog 🐕 

watercourse

Mad Dog_2 said:

You really need two people on those radiant staple up crawl space jobs. One to feed the pex and keep turning to stop kinks and one to fasten to the plates.  Technically you're cheating by crossing under the joists but you gotta do what you gotta do.  It's not the end of the world. Mad Dog 🐕 

Thanks. If I'm technically cheating does that mean it wouldn't pass inspection?

EBEBRATT-Ed

@watercourse LOL most inspectors won't go in a crawl space or on a roof .......at least around here.