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.

Bob's build 8-18 2.jpg
Bob's build 8-18 12.jpg

**DanS** · 11-18-2014, 08:56 AM

We will put in-floor radiant heat when we build.

The only question I have for the folks who have installed it in the basement slab (versus in the first floor) is does the basement get excessively hot? The thermostat would obviously be on the main floor, so if it's asking for 60 degrees, will the basement end up at 70 degrees? Or does it work out more even than that?

We've got two 200 gallon insulated stainless hot water storage tanks, so we're ready for the solar drain back system, the only question to answer is whether to put the radiant in the basement, or in the floor itself. Either way we will have radiant in the bathroom, and probably kitchen, so it will be on the first floor at least a little.

My parents installed in floor radiant heat powered by the sun, and it's so nice to keep that part of the house at 70 degrees all day long, no matter what is going on outside and not have to worry about the gas bill. And REALLY nice to take a shower with a nice and toasty floor.

Dan

**thoner7** · 11-19-2014, 04:46 AM

You would want two zones for the basement and first floor. It's very easy to have multiple zones

That is impressive that they get all of their heat from the sun!?!?

**WNYcabinplannin** · 11-21-2014, 05:42 PM

I have only the basement with radiant. It's a slow gentle heat. If I put the radiant on, 70 say- the main floor gets there slowly. It doesn't go crazy in the basement. With the basement door open it balanced faster, but not much. Mind you I ended up with three heat sources. The woodstove, and two Mitsubishi ductless: one in the kitchen on main floor and one in the upstairs master. I got them mostly for the AC, but they heat the place fast.
So let's say I keep the radiant at 58 when I'm gone for a week. I come in, hit the two ductless to 68, hit the radiant to 70, and start the woodstove.
Within 20 minutes the ductless cut off bc the woodstove is rocking. The basement has come up to 65, and gets to 70 in another hour.
Woodstove becomes the only thing running fast. I get a 12 hour burn if I pack it...
If I sleep in and the stove is cold, the radiant will have kicked back on and the whole place is toasty...
Ok there's my radiant situation over explained...

**DanS** · 11-25-2014, 01:37 PM

Originally Posted by thoner7

You would want two zones for the basement and first floor. It's very easy to have multiple zones

I should have specified: the basement will be just utilities and storage for us.

That is impressive that they get all of their heat from the sun!?!?

Very impressive. It's pretty cool being able to leave the house to remain at, say, 68 degrees while you're gone--because the heat just isn't costing anything. ...which is precisely what we're after.

Originally Posted by WNYcabinplannin

I have only the basement with radiant. It's a slow gentle heat. If I put the radiant on, 70 say- the main floor gets there slowly. It doesn't go crazy in the basement. With the basement door open it balanced faster, but not much. Mind you I ended up with three heat sources. The woodstove, and two Mitsubishi ductless: one in the kitchen on main floor and one in the upstairs master. I got them mostly for the AC, but they heat the place fast.
So let's say I keep the radiant at 58 when I'm gone for a week. I come in, hit the two ductless to 68, hit the radiant to 70, and start the woodstove.
Within 20 minutes the ductless cut off bc the woodstove is rocking. The basement has come up to 65, and gets to 70 in another hour.
Woodstove becomes the only thing running fast. I get a 12 hour burn if I pack it...
If I sleep in and the stove is cold, the radiant will have kicked back on and the whole place is toasty...
Ok there's my radiant situation over explained...

Gotcha. Good to know. I assume your basement thermostat is located in the basement?

Dan

**thoner7** · 11-26-2014, 08:00 AM

Do you have to be out west where the sun actually shines to get those kind of results?

**loghousenut** · 11-26-2014, 08:23 AM

Originally Posted by thoner7

Do you have to be out west where the sun actually shines to get those kind of results?

Solar heat is mostly for those of us to live out west. There is precipitation heat for anyone who lives near Rod. You may want to back up with a good wood stove to combat the humidity.

couldn't help myself

**DanS** · 11-26-2014, 06:44 PM

Originally Posted by thoner7

Do you have to be out west where the sun actually shines to get those kind of results?

I don't know if it's so much an east vs. west issue, or a low vs. high altitude issue. My parents place is at just under 7000 feet, and mine is at roughly 9000. When the sun shines, it is HOT. There's very little atmosphere between us and the sun, so I suspect that makes the solar heat much, much more effective.

Dan

**pip1972** · 10-19-2016, 03:09 AM

I am going to resurrect this thread for a brief moment. We are planning on building a 2 story garage with the foundation starting next fall. I believe we will be using PEX in the garage floor. I read through various links earlier in the thread. I am convinced that is the correct option for the pad. I've read info on the tankless and that seems to be a subject for debate. I do like the "looks" of the water heater on the radiant site.

Here is question #1. For the upstairs I can not determine if radiant (pex under the 2nd floor/ceiling of the garage) is the most efficient for our application/location. The garage will be located in the central Michigan with in sight of Lake Huron (lower peninsula for those out west). I understand multiple loops, zones and having other sources, hence question 2.

Question #2. If a wood stove is also part of the equation, can it be located on the slab and the heat routed to the 2nd floor? I am still young and dumb and can carry firewood to the 2nd floor. In 20 years that will not be the case.

Your thoughts, opinions, experiences, critiques are welcomed. I'm doing it once and want to have the best sources of heat with minimal cost (as does every one else).

**panderson03** · 10-19-2016, 04:18 PM

1 we have pex in the 5 inch slab of our basement cement floor. works great to heat the whole garage including the loft

**pip1972** · 10-19-2016, 05:07 PM

The loft is heated just from the heated pad? Or is there a heating source in the loft? Is the loft insulated from the garage/slab area? Is there a living area in the loft? What do you use for the PEX heating source ?

**rckclmbr428** · 10-20-2016, 02:10 AM

Heat rises

**panderson03** · 10-20-2016, 06:21 AM

Originally Posted by pip1972

The loft is heated just from the heated pad? Or is there a heating source in the loft? Is the loft insulated from the garage/slab area? Is there a living area in the loft? What do you use for the PEX heating source ?

the loft is heated just from the PEX in the cement slab. there's a game room/man cave in the loft (not necessarily a living area .... dog house maybe?).
we have a boiler for the heat source though I read that a plain old water heater would work too!

**BoFuller** · 10-21-2016, 07:13 AM

I imagine the pad heats the loft very well. My woodstove cooks us out of the upstairs. We have no heaters upstairs and usually sleep with the windows open, even when it's below freezing.

Heat rises. I'm concocting a plan to duct the heat from the ridge pole area back down to the 1st floor bathroom.

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**oldtrapper** · 10-21-2016, 07:42 AM

Just to clarify, warm AIR rises, heat radiates in every direction from hottest to coldest. just saying.

Learned this the hard way, with an earth sheltered house, back in the 80s.

**pip1972** · 10-21-2016, 09:22 AM

Thanks for clarifying. Now, if the second floor is more of a living space then a loft would just running vents to pass the warm air from the 1st floor to the second be a reasonable solution? I still believe a heating source should be used. Most of the 2nd floor would be hardwood or tile. Could PEX be run in the floor be a good idea to ensure appropriate heating? I would consider either an outdoor boiler or just using a boiler in the garage area. Using a small tractor to bring wood in. One more thing. Would there be any square foot mind or maximus to make that work as planned?

**pip1972** · 10-21-2016, 09:26 AM

Ugggh spell check. I am referring to the second floor above.

Would there be any square foot minimums or maximums to make that work as planned? Meaning size of the pad to heat the structure with assuming no heat source in the living area above.

**pip1972** · 11-17-2016, 02:24 AM

Outdoor boiler? Do you run that straight into the pad? What temp enters the pad?

**pip1972** · 11-17-2016, 02:29 AM

Your wood stove is on the first floor? What is the square footage for downstairs/upstairs? Do you use PEX in the slab (assuming you have a slab)?

Originally Posted by BoFuller

I imagine the pad heats the loft very well. My woodstove cooks us out of the upstairs. We have no heaters upstairs and usually sleep with the windows open, even when it's below freezing.

Heat rises. I'm concocting a plan to duct the heat from the ridge pole area back down to the 1st floor bathroom.

Sent from my iPad using Tapatalk HD