How crutial is radiant in floor heating in the basement?

Gordy

As hot rod pointed out the logistics of the concrete pour, and how the tubing will be protected are huge.

geboy

Yes as my contractor said they will be wheel barreling the concrete around. He said that he will notify them to bring wooden sheets to put down, but I was going to pressurize the system with air before they pour. So hopefully leaks and damage will be minimal

Gordy

None, you don't want to be digging for, and fixing a leaker buried in concrete the middle of a pour.

hot_rod

You want to be there the day of the pour!

Have concrete boots on, a camera, and a pocket full of repair coupling in the event they snag or damage a tube.

Keep a 100 psi pressure test on from now until you finish the connection to the boiler.

At 100 psi you will defiantly see where, if they puncture a tube.

Use a video function on your camera or phone to document the tube layout. Some mapping is helpful should you ever want to drill into the slab later on..

I would not use pex al pex on a job where the tube is fastened to mesh or rebar and they are wheeling the mud around, too much potential to get kinking.

Gordy

And have a compressor handy to repressirize the lines of a repair happens to take place.

My previous statement is oriented to what you need to communicate to the concrete crew. No kinks, or leaks! Things happen though. A kink is worse than a leak. At least you will be able to know, and repair a leak. A kink can rear its ugly head when a loop(s) have little flow, or no flow.......after the Crete is hard.

geboy

Alright now you guys are scaring me

Gordy

Just preparing you.

Zman

It will probably be fine.
Concrete guys are probably the hardest subs to direct.
I would recommend bribing with donuts in the morning and a cooler of cold beer when they finish. They should be aware the beer exists when you feed them the donuts, but I would not give them any until they are about finished. Think of yourself as a zoo keeper. I am not kidding, you will be amazed how far this $50 investment will go.
I doesn't hurt to inspect the point on the wheelbarrow where they tip. A good time to do this is when they are distracted by the donuts. I have seen them get razor sharp from wear. You can put a strip of wood over the tip with wire and duct tape.
With 100 psi you will get a very loud audible if they hit one.

Gordy

Prepare for the worst. Hope for the best, and everything will be fine. Zmans advice is certainly worth the cost.

hot_rod

The Crete Heat does a good job of protecting and keeping the pex down. Doesn't look like much of the wheel will touch it.

When you tie pex to remesh all the tube is exposed to the wheel and tipping point on the wheel barrow. The remesh is also more of a tripping hazard.

If you go with foam sheets buy or rent a foam stapler, it is quick and easy compared to mesh. I put mesh over all the turns to help keep them in place also.

The pex will be stiff when cold, keep it warm as long as possible.

An un-coiler also simplifies the install. but for that small area just roll it off your shoulder if you don't have an un-coiler.

geboy

Thanks a bunch guys, I really appreciate it!

overpop

My experience from my self installed installation: Foam sheets under and perimeter of foundation. 6" x 6" mesh. Pex Al Pex wire tied, 4 loops concrete poured over. Then regular pex for entire 1st floor. The one time I turned on the basement with all 4 loops it felt like a sauna. Very uncomfortable not to mention the Buderus was working overtime to heat the mass up. So, here's what I ended up doing. I ran through one loop, and put it on a timer. The first floor was on a thermostat and that alone was enough to keep the basement comfortable. This was an unfinished basement and the radiant reflector was luan with the special shiney foil facing up.

Zman

overpop said:

My experience from my self installed installation: Foam sheets under and perimeter of foundation. 6" x 6" mesh. Pex Al Pex wire tied, 4 loops concrete poured over. Then regular pex for entire 1st floor. The one time I turned on the basement with all 4 loops it felt like a sauna. Very uncomfortable not to mention the Buderus was working overtime to heat the mass up. So, here's what I ended up doing. I ran through one loop, and put it on a timer. The first floor was on a thermostat and that alone was enough to keep the basement comfortable. This was an unfinished basement and the radiant reflector was luan with the special shiney foil facing up.

It is true that a high mass slab can suck BTU's when coming up from a cold start.
As far as turning the place into a sauna, you are running a water temp that is way to high. In most applications you don't need more than 120 degree water on the design day for a properly insulated concrete slab. On a typical day the temp should be much lower. Outdoor reset and proper temps are mandatory with high mass slabs.

Gordy

The sauna part is usually moisture in building materials of new construction being driven out. In this case concrete.

MikeG

A local farmer acquaintance built a 150X80 farm shop, $1.3 million worth. Has his shop, parts storage, office etc. He has all radiant floor. I saw some of the install. He used 1" of this stuff for under the floor www.The barrier.com. I told him I didn't think it was enough, but he had it designed by someone and everything was contracted out. . It's a expandable foam. Comes in a roll with adhesive peel and stick tape for the seams. I think they only did 1" of ridged foam around the edges. They used 6x6 wire mesh mats and tied the 5/8" pex to it. I think on 12" centers. There were a boatload of zones and loops. They used rebar on chairs and poured 6" of concrete. They did pump all the concrete so no issue of wheeled buggies or wheel borrows. He heats it with 2 IBC LPG boilers. This is his fourth winter. I've been in the shop in the winter and it is comfortable when his mechanics have to work on equipment. This is different than a living area. I have no idea how much LPG he goes through. He does have a 30K LPG tank for his grain dryers, but he does use a couple of 500 gal tanks for his shop. I don't think he knows or cares what it takes to heat it. The Crete Heat definitely solves a lot of the installation issues. My limited experience is to get 2" of ridged foam under and get the thermal break around the perimeter of 2" if possible all the way to the footer. Yes it will look like the floor is floating on the insulation but the under slab product should have the compressive rating to handle it.

Zman

Generally, "The Barrier" has very low comprehensive strengths and would not be very suitable for heavy equipment traffic. A couple of their products are 25 psi which would be suitable for very light traffic. Their other products are 10 psi.
A 4" concrete slab applies around 4 psi by itself.
http://www.thebarrier.com/under-concrete-insulation.php

MikeG

Zman,
I have a piece of the stuff it was 3/4" not 1" still 8.2 R from the literature. I thought it was bit thin, both in thickness and R value. What is going to happen to it with that low compressive strength? I may have to stop in to his shop and see if he has any performance info on his setup. He brings in big tractors, planters, semis and combines.
I don't do this type of work except on my own house. I did a small utility room 12x14 in my house and used 2 layers of the 1" blue Dow board, 4" of compacted gravel with 60' of 3/4" soft copper buried in it and then 4" of concrete with porcelain tile over it. I realize the copper in the gravel may have a limited life span. I also put 1/2" pex AL in thin plates under the ceiling drywall if the floor ever copper ever pinholes. I run 110 degree water through the ceiling before it goes to the floor. It's a real nice radiant sandwich. Best room in the house. The floor is not warm but not cold. Keeps the boots, gloves and carharts nice. I did leave a bit of the ceiling insulation out on a small area that has a bathroom above it. I don't get that much upward heating as I thought. I should have just run some pex and plates on that small section.

Zman

You just touched on the other issue I have with this product. The R-8.2 is absolute BS. That is if you count the R-value of 6" of dry gravel as part of the assembly. Nobody tests this way and to represent the product this way is deceptive. The real R-value is closer to R-3.

My guess is that the concrete slab and the vehicles in your friends shop crushed the insulation to some extent right away, reducing the R-value further. If the slab was heavily reinforced, it probably squished the insulation pretty uniformly minimizing cracking.

I was burned several times in the early days of radiant by fake values. Never again...

MikeG

Now I see. So what is the 25 degrees that they test at, the subgrade temp the air temp or the difference. I see the material only R changes from 25/75 degree. So in their test the 6" of gravel has a higher R than the foam.

Zman

MikeG said:

Now I see. So what is the 25 degrees that they test at, the subgrade temp the air temp or the difference. I see the material only R changes from 25/75 degree. So in their test the 6" of gravel has a higher R than the foam.

I think it is the temp it is tested at.
I wish all AHJ's were as sharp as mine. They would fall over laughing if I submitted this one...

Gordy

You have to remember as temperature delta increases r values increase. Most standard insulation is tested at 70 degrees for its rvalue. Sips for example rate their rvalue at 40-45 degrees. So their rvalue are a bit higher.

Ditch the barrier for reasons stated.

geboy

Pic update. This was completed yesterday, luckily the concrete got pushed back due to the carpenters being pushed back cause of rain.

Harvey Ramer

You might want to look over it and add a few more zip ties. They look a little sparse in some areas. Don't want the tubing coming up during the pour.

Also, where are the leaders coming up? I see a plywood box where it looks like they end up in? Normally, you would use some type of bend supports and bring them up out of the slab by 2' or so. Then manifold them and put the tubing under a pressure test till the boiler is ready to be installed. Also, you should have someone on site, with a few couplings and heat shrink tubing, in the event a repair has to be made while the concrete is being poured.

Gordy

If you can pick the tubing up between ties with little effort it will float up.

Curious as @Harvey Ramer about the box, and leaders.

Mesh should be lapped.

Means, and methods of pouring?

hot_rod

12- 18" max on ties. The loop ends tend to float most, 3 ties around the loops.

Tube spacing looks 15- 18"? probably fine for a basement load.

bio_guy

Anyone considering radiant in slab should be aware that it limits the use of the space due to the extreme inertia. For example, you are not going to exercise heavily in a relatively cool area and then relax with the family over a movie in the same room an hour later without blankets.

This comment is a little late for the comment about no insulation under a slab because the heat will warm the soil. I can't believe that it is hard to grasp that the earth is effectively an infinite sink for the heat from a home.

geboy

I believe it's 7/8's pex and it looks like the ties are about a foot at least around the bends. May have to go and add some on the long runs.
The pex has been pressurized since Friday. The installer is going there today to double check the pressure. The box is where the hardlines meet the pex...I believe. The box also acts like a little shelter box while pouring to form the concrete around the 90* elbows.

Gordy

I was wondering....... He put 90's at the loop ends?

Gordy

bio_guy said:

Anyone considering radiant in slab should be aware that it limits the use of the space due to the extreme inertia. For example, you are not going to exercise heavily in a relatively cool area and then relax with the family over a movie in the same room an hour later without blankets.

This comment is a little late for the comment about no insulation under a slab because the heat will warm the soil. I can't believe that it is hard to grasp that the earth is effectively an infinite sink for the heat from a home.

Usually if people are fitness fanatics they will dedicate an exercise room in the space. Thus being on its own zone.

Zman

bio_guy said:

Anyone considering radiant in slab should be aware that it limits the use of the space due to the extreme inertia. For example, you are not going to exercise heavily in a relatively cool area and then relax with the family over a movie in the same room an hour later without blankets.

This comment is a little late for the comment about no insulation under a slab because the heat will warm the soil. I can't believe that it is hard to grasp that the earth is effectively an infinite sink for the heat from a home.

@bio_guy

If it ones intention to heat a room to 60 degrees for workouts then heat it to 70 degree a few hours later for family time, radiant heat would not be a good fit. I believe the OP is just looking for nice comfortable heat with no temp setbacks. For this application, a setup with high mass radiant , proper insulation and outdoor rest will work great.

The earth does make for an infinite heat sink. If the OP is intending to keep the living space at a balmy 50 degrees (or whatever the ground temp happens to be) then I think the insulation is a horrible idea.

What needs to be "grasped" is that heat sinks are a two way street. When you put a 75 degree slab in direct contact with 50 degree earth, you are infinitely giving up heat to the earth. You are not somehow heating the earth and storing energy, you are just giving away energy to a mass so large it could never be heated. Everything will eventually achieve thermal equilibrium, insulation helps slow this process...

geboy

Just went to the house to check out the install. Zip tie spacing is about 18" max and I tried picking one of the pex tubing up in between the 18". Couldn't get it above an 1" before it pulled the whole wire mesh up with it, so it all seems pretty sturdy.
Yes I believe they use hard line 90* bends out of the floor. So pex is all horizontal, and then 90* into hard pipe.