Pex-B for radiant floors

RedMonte85

Is Pex-B tubing from RHT the correct tubing to use for an above subfloor install and a ceiling install? This has the oxygen barrier, is it going to cause noise issues? Should I be using something else? The tubing is 1/2" if that matters. Thanks

hot_rod

as long as you fasten it tightly in the plates it should be noise free. Generously sized holes with insulators where you penetrate wood floor or joists.

RedMonte85

Are there thinner insulators than what I see online mostly? For 1/2" pex the insulator hole needs to be around 1 1/4" or 1 1/2". Some of my piping will need to go through ceilings joists (2x6) and I would prefer not to swiss cheese them with large diameter holes.

hot_rod

plenty of joist drilling charts online, usually 1/3 the joist depth for a hole.
1-3/8" is a common hole size for insulators, that should be fine in a 2X6 (5-1/2")

RedMonte85

The attic is not used for storage and I will be blowing about 16" of cellulose up there in the near future. Would installing "raceways" along the tops of the 2x6's for the supply and return runs be acceptable? Using nail on clips or something similar to hold the pex ?

hot_rod

RedMonte85 said:

The attic is not used for storage and I will be blowing about 16" of cellulose up there in the near future. Would installing "raceways" along the tops of the 2x6's for the supply and return runs be acceptable? Using nail on clips or something similar to hold the pex ?

I would suggest protecting that attic pex some how. Maybe a thin masonite layer to try and keep rodents at bay.

RedMonte85

I shouldnt have any issues with rodents, had the space between the top plate and the roof sheathing baffled and foamed. My cat has eliminated the vole problem in the yard. Never the less, rodents can manage to get in anywhere. The supply and return lines go over 3 bedrooms and 2 bathrooms. I cant floor over the tops of the joists because of the insulation going there. I dont see a way of ever covering it honestly, unless I spray foamed around it.

psb75

Rodents do not like borax treated cellulose insulation. Its too loose.
They can't 'structure' it to live and travel through.

mattmia2

They sure seem to like the cellulose in my attic...

Ironman

Good type A pex, like Rehau or Uponor doesn't cost that much more in the entire scheme of things, but has a 200 year life expectancy vs 25 years for the stuff that you're considering.

IDK your climate, but if freezing conditions normally occur, the attic will be a freezing spot too.

mattmia2

Pex b has a 25 year life expectancy? So home depot is basically selling the new polybutylene?

Ironman

> @mattmia2 said:
> Pex b has a 25 year life expectancy? So home depot is basically selling the new polybutylene?

Do you mean to say that you’d go to Home Depot for radiant tubing?

rick in Alaska

The main thing I would be concerned about with pex-b is that if you kink it during installation, which is easy enough to do at the bends,you would have to cut out that section and put a splice in, but with pex-a, you can use a heat gun and fix it. Personally, I would not want a buried splice in my floor.
Rick

mattmia2

Ironman said:

> @mattmia2 said:

> Pex b has a 25 year life expectancy? So home depot is basically selling the new polybutylene?



Do you mean to say that you’d go to Home Depot for radiant tubing?

I would if they carried oxygen barrier pex a. I chose pex a because it can use expansion fittings, crimp or compression fittings on pex don't seem like a long term solution to joining it. i would prefer to not have to buy it in increments of 100'. deterioration at different rates would be a huge factor in my decision as well.

If deterioration is an issue for heating, it will also be an issue for domestic water since some of it will be exposed to similar conditions in attics and where it runs near heating equipment and such.

GroundUp

25 year expectancy versus 200? Do you happen to have some data on that @Ironman ? I find it hard to believe that the same material in one form can outlast the same material in another form by 800%.

@rick in Alaska you can absolutely repair pex-b kinks with heat. I've done it dozens of times and always pressure test to 150 PSI with no deformation

Ironman

GroundUp said:

25 year expectancy versus 200? Do you happen to have some data on that @Ironman ? I find it hard to believe that the same material in one form can outlast the same material in another form by 800%.

@rick in Alaska you can absolutely repair pex-b kinks with heat. I've done it dozens of times and always pressure test to 150 PSI with no deformation

Rehau has data on it and I'm sure there's plenty on the net about the life expectancy of pex B.

As far as kinking goes: it only takes a couple of bends, back and forth, on a piece of type B to kink it. Ive been in classes with Rehau type A where it was intentionally bent back and forth for a 1/2 hour and still never completely kinked.

Im not aware of any brand of type B that the manufacturer approves of repairing with heat once its kinked.

Maybe you have something on that that I don't know about. I'm sure hot_rod probably could shed more light on the subject.

GroundUp

ASTM standards require a minimum of 50 year lifespan from any pex tubing, and both Rehau pex-A and Everhot pex-B are rated at 50 years while Uponor pex-A is rated at 100. This tells me it's little to do with the crosslinking process and a lot to do with the product.

B, in 1/2", is very easy to kink I will agree. I can't imagine any MFG of pex-B recommends repairing a kink with heat, but having done it a number of times I know very well that it works nearly the same as it does with pex-A; which is also pretty darn easy to kink in 1/2".

rick in Alaska

I would be very nervous about that repair. If I am not sure if a product is a or b, I just bend it a few times and literally break it in half. You can't do that with pex a. But, I don't know, maybe one small kink would be ok to repair with heat.
Rick

GroundUp

I guess I've never seen that side of B. Yesterday when I was wandering around the shop taking some measurements for Zman in another thread, I grabbed a short chunk of Everhot 1/2" B and kinked it purposely. Then worked it back and forth maybe 40 times and slowly heated it with a MAP torch and it returned to almost original form. After it cooled, I was squeezing it with a pliers and it seemed to be pretty close to original integrity but I did not pressure test it. The vast majority of my work is radiant slabs and I have yet to find a reason to install A. One minor kink per 20,000 feet of tubing is about my going rate, which I do repair with heat on-site with great results. The price of A is more than double the price of B, and I always give the option but of the 85,000 feet of radiant I sold in 2019, exactly zero people opted for the A and I don't blame them.

rick in Alaska

That is interesting. I think I have a couple pieces of other brands of pex b laying around, and will see what happens with them. Every piece I have ever bent more that 5 times I can pull completely apart, but maybe everhot has something different added? But yeah, pex b would definitely save a lot of money if you are using it a lot.
Rci

hot_rod

I’d worry more about the quality control, virgin resin, manufacturing process, etc then I would the type of Pex

Stick with a known, respected brand. A properly done splice should not be a big deal. With composite fittings and Pex expander rings Pex A can be spliced in slab if needed without corrosion concerns

hot_rod

I wonder what an heat gun does to the wafer thin EVOH oxygen barrier on the tube?

GroundUp

Something like Viega I'm sure is probably a higher quality B than say Nibco from Menards, I guess I use primarily Everhot because of the price point at my supplier and the luck I've had with it. It's definitely not as much fun to work with as HePex or other A, but I'll gladly trade the extra hassle for the extra cost. A good tubing uncoiler and technique goes a long way

psb75

Just to add some confusion to the mix: what about Pert®? Its orange and quite flexible and has O2 barrier and sold at F.W.Webb. I don't think its expandable.

mattmia2

you have to hold the heat back from a distance and heat it gently and slowly to keep from burning the oxygen barrier off. I have seen it curl up and char around the edges when softening pieces to remove them from brass fittings to reuse the fitting from a temporary setup.

Ironman

psb75 said:

Just to add some confusion to the mix: what about Pert®? Its orange and quite flexible and has O2 barrier and sold at F.W.Webb. I don't think its expandable.

Yes, you can use ASTM 2080 (Rehau) cold expansion fittings with it. I confirmed this with one of Roth's engineers some years back when I saw it stated in RE Michel's catalogue.

PERT is a good choice that's less expensive than pex A, but superior to pex B.

GroundUp

PERT is also a lot less resistant to abuse, at least the Oil Creek variety I've used. The mud monkeys aren't often very cautious when pouring a slab and will squash PERT with a loaded buggy if they miss the plywood. I'll use it for other things but not slab applications after that.

hot_rod

GroundUp said:

PERT is also a lot less resistant to abuse, at least the Oil Creek variety I've used. The mud monkeys aren't often very cautious when pouring a slab and will squash PERT with a loaded buggy if they miss the plywood. I'll use it for other things but not slab applications after that.

Will the PERT tube squash with a 100 psi air test on it?

GroundUp

Actually yes. Not nearly as much as it does deflated, but it does. I've only used it in slabs a couple times but one of them I made a little test area and what I didn't like was the PERT expanded at 100psi, leaving air space around the tubing after the concrete cured and tubing was depressurized. The next one I only ran at 10psi to try to curb that, and there were a few areas I saw them drive over with the power buggy that flattened the tubing like a regular poly water line and it just kind of stayed that way. I love PERT for joist installations due to flexibility but between the two aforementioned issues, I won't put it in a slab again. At least not Oil Creek anyway, I'm sure Roth is a considerably better product but is out of the price range 99% of my customers will pay.

RedMonte85

Pex-B is really only rated for 25 years? Everything I have read seems to point towards it lasting 50+ years.

Zman

As Hot Rod said, the quality control is going to be better with Pex-a. Not only is it a superior product to begin with, the manufactures of Pex-a have a lot more experience and frankly more at stake if there is an issue.