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In slab and staple up radiant design help

We are about to start building our new house next month and I’m adding radiant heat in the basement slab and also for the first floor. House is a 1850’ ranch, in Northeast Pa. R23 in the walls, R50 in the attic, basement ceiling R30. Basement is 10” poured walls that will be finished later on. I’ll be adding 2” XPS under the slab and on the sides, then tying the pex to the wire mesh prior to them pouring concrete. I’ve been on Slant/fin going over my heat loss calculations. But for now I want to at least get the rough in done while construction is happening. Heating the system will happen later on, as a closed system with a boiler of some sort.

A couple questions I have are:
I’ll be using 1/2” O2 pex, 12” on center in the slab, and the same for the first floor in the joist bays stapled up with heat transfer plates at 8” on center. I’m planning 1 zone for the basement, and 2 zones for the first floor.

What type of Pex is recommended for this install? I have recieved a couple quotes from some online suppliers and they all recommend using different types of Pex.

Where can I go to get a design layout for this install and/or purchase everything from? I know I’ve read some reviews on here regarding the companies that have sent me quotes, and I don’t want to break any rules, so I won’t mention any sites. But just looking for a little guidance so I can place the order for everything when I’m ready.

Any other tips recommended for this install would be appreciated.

Figured I would ask here since there is a ton of knowledge on the forum.


  • Ironman
    Ironman Member Posts: 7,379
    edited August 2019
    The best thing you can do is get design help from a pro BEFORE you start purchasing components or plan on any tubing layout. It's gonna require more than just having one of us answering a few questions.

    There are several men on here that can do it if they have the time. I don't, but be patient and usually someone on here can.

    As you've apparently noticed, you should in general avoid online peddlers.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Zman
    Zman Member Posts: 7,574
    What you are describing will work very well. Be sure to keep your loops in the ~250' range.
    When it comes time to set and pipe the boiler, you will need to determine whether the upper and lower levels will need different supply water temps. You will do this by comparing the heat loss of the space to the output of your zones at a given supply water temp. Usually the basement will need lower temps as the concrete conducts heat better and the heat loss is likely lower that the upstairs. There are a variety of ways to make this work.

    As for Pex, there is Pex-A, Pex-B, Pex-C and Pex-Al-Pex. For heating projects you must use a tubing designed for heating which has an O2 barrier. Most brands have one product line for potable water and another for heat tube.

    For most projects like yours, it is advisable to go with Pex-A from Uphoner or Rayhau they cost a little more than some of the other brands but have historically low failure rates.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • hot_rod
    hot_rod Member Posts: 22,254
    If there is a radiant pro in your area, they usually have the best data for designs specific to the climate, as well as product selection that is well supported in your neck of the wood. They would know local sub contractors that are radiant friendly.
    Good to have a concrete crew that respects the tube.

    A load calc performed on a radiant specific program by a knowledgable radiant contractor will give the exact details, tube spacing, circuit length, flow rates, SWT, etc.

    Certainly the load calc and design could be performed by any knowledgable radiant person, near or far.

    Supply houses, reps, manufacturers offer this service, sometimes a small fee is required.

    If no one is listed here at HH in your area, check with the local plumbing and heating suppliers in the area that sell radiant.
    Contact the manufacturers or their reps for boilers, pumps, tube, etc to get a list of contractors in the area, these folks usually can help steer you to the best.

    A lot of the best radiant guys and gals are "underground" :) their work is all word of mouth and they may not advertise. You need to ask around and get in the loop.

    Some contractors welcome help from the homeowner, I always did, save you some $$ and make new friends.

    IG and FB groups are another place to look at job pics and talk to some of the best hydronic folks.

    The A type pex are the most flexible, to use especially in tight spaces. 3/8 is sometimes preferred by installers for joist bay work, but more and shorter loops will be the trade off.

    If you get good quality transfer plates with a tight tube fit, regular pex is fine. PAP has less expansion concerns it the tube is expected to be moving around. PAP is tougher to work in joist spaces and can be easily kinked.

    I'd stick with a name brand barrier pex, plenty to choose from, some advertise on this site. Uponor, Rehau, Mr Pex are a few brands that use an expansion fitting, many installers prefer that system for full flow.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • onemoosehorn
    onemoosehorn Member Posts: 5
    Thanks everyone. Yes plan is the keep all the loops as close to 250’ as I can. I will be using an O2 barrier pex, but was curious what type everyone recommended and why. I’m in the research phase now so all this helps.
  • GroundUp
    GroundUp Member Posts: 1,924
    For staple-up I'm really liking the PE-RT tubing myself. Flexibility is far greater than any Pex-A and I feel there is less noise. I alternated loops in my own house with PE-RT and He-Pex, just to give the PE-RT a try, and have been using PE-RT ever since on customer jobs
  • onemoosehorn
    onemoosehorn Member Posts: 5
    > @GroundUp said:
    > For staple-up I'm really liking the PE-RT tubing myself. Flexibility is far greater than any Pex-A and I feel there is less noise. I alternated loops in my own house with PE-RT and He-Pex, just to give the PE-RT a try, and have been using PE-RT ever since on customer jobs

    I’ll look into the PE-RT tubing also.....