PEX radiant sub-floor heating under basement floor

**Strongbow** · 11-09-2014, 03:04 AM

Does anyone have any experience with this? Problems/issues? Benefits (other than not having to hear a jet engine start up when the heating system kicks on)? Cost? How long do they last in the real world? I'd hate to set my heart on one of these only to find out after the fact that I need to smash my basement floor every ten years. Also considering masonry heater. Maybe a combination of masonry and radiant subfloor with PEX. We'll see.

**WNYcabinplannin** · 11-09-2014, 05:15 AM

Do it!
I put radiant in my basement. 3 300' loops. I put an R10 shielding down first, then the mesh grid. Pex zip tied to the mesh. 6" poured slab.
I'm in upstate NY with COLD winters. The radiant combined with my ICF block basement (with walkout) is so comfortable. I got a Navien combo-boiler. One zone just for the radiant, one for the domestic. I can heat the whole home from the slab up. Wasn't even necessary to run 3 zones under the sub floor.
The cost savings, the quiet ductless heat, and green energy joy... Huge boost to resale value- completely worth it. If you install right you'll be set. Use a good tankless water heater like Navien or Boxi.

**rreidnauer** · 11-09-2014, 06:31 AM

Yea, for the PEX portion, as long as you insulate under the slab, and have no fittings embedded in the slab, it's a slick system that will last for generations.

The tankless or condensing boilers, it's too early to make the call. A lot is being asked of these ultra compact systems, and I think getting long life out of them will be a challenge. Probably not a good place to skimp on spending if you go that route.

**btwalls** · 11-09-2014, 07:17 AM

look into ground source heat pumps as an add on if you have the land. Can do most of the work yourself.

**thoner7** · 11-09-2014, 08:05 AM

I have found this website helpful. http://www.radiantec.com

They seam to have done some studies on the subject. They also recommend using an H2O tank rather than a boiler.

**rocklock** · 11-09-2014, 10:45 AM

Originally Posted by Strongbow

Does anyone have any experience with this? Problems/issues? Benefits (other than not having to hear a jet engine start up when the heating system kicks on)? Cost? How long do they last in the real world? I'd hate to set my heart on one of these only to find out after the fact that I need to smash my basement floor every ten years. Also considering masonry heater. Maybe a combination of masonry and radiant sub-floor with PEX. We'll see.

Be sure to use the correct PEX is a must. Something like Oxygen resistant is what I used...

**rckclmbr428** · 11-09-2014, 11:28 AM

Here's one we did in Wisconsin a few months ago, if I can find land flat enough this is my plan as well.

**Strongbow** · 11-10-2014, 12:12 AM

Do they heat the concrete evenly? It seems like there would be thin stripes of heat and wider stripes of cool concrete.
Btw, a most definitely on ICF.

**TAB** · 11-10-2014, 08:23 AM

Concrete is a very good conductor of heat. As long as the loops are spaced appropriately there wont be cool concrete. Plan ahead and run pex closer together in areas that you want a little more heat (at the kitchen sink). Radiant heat is hard to describe, it's something that needs to be felt, much different than forced air. One word of caution though, radiant heat takes a very long time to heat a home, but once it's reached the desired temp it does an excellent job. I wouldn't recommend it for a weekend cabin since it takes so long to get to desired temperature without supplementing from another source.

**dakota.abe** · 11-11-2014, 04:08 AM

I helped a neighbor install the pex, etc. last summer in a 40 x 80 timber frame home/shop. The Benchmark Foam slotted Styrofoam panels make it simple to install the pex – you just lay the pex down and step on it to push it in. The slots are spaced every 6” to allow for variable spacing based on floor plan. Staples can be used in a few spots as needed but I would hate to staple the whole floor.
I know the early pex tubing had problems (but a lot less than copper) with leakage but the oxygen barrier pex seems to be the answer. It is very important to keep the tubing length consistent.
A lot of people here are heating the water with wood and solar (can be DIY) is also a viable option.
We are just starting to build a timber frame structure that will be our home and storage while building a LHBA 30 x 30 and plan to use in-floor radiant in both.

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