OT In floor hot water heat??

I have a question for anyone who has any experience with in floor heat. Our tractor club put up a new building last summer with tubing in the floor for heat. Building is up, but heat is not hooked up yet. Which is more economical for heat source, hot water heater or a demand type heater? I know the system needs antifreeze in it, but will it make the cement more likely to crack if the heat is not used after filling system and start up? We haven't finished hooking up the system yet, some of the guys are saying it has to be heated or the cement will crack and possibly break the pipes, others say that it won't make any difference. We really don't want to pay for heat when we are not using the building, but we don't want to run the risk of the floor cracking and possibly breaking the tubing. Building is fairly well insulated, but the temps have been below 0 for the last week or so. What are your experieces? Thanks, Chris

Can't and don't really want to answer the "what if's?", but floor heating is something that will spoil you. Not really something that you can turn up and down and notice the difference in a day though. If it was me, I'd get the most efficient 30 gallon (maybe even smaller) electric (because it would be unattended) water heater I could find, wrap it in a thick blanket of insulation, and set it at 40-50 degrees and hook up a circulating pump on a thermostat. Walking from 0 to 40 degrees is a nice change but, if you know you want it warmer on a certain weekend, just raise the temp on the heater a few days ahead.

Enjoy...

Dave

What dave2 said I second, it"s not like I"m cold let"s turn up the heat and walla I"m toasty. You"re better off setting it at comfortable level and leaving it that way likewise the cooldown is the same way. Without going into engineering details of which I"m not an expert. When you said copper I"m suprised because last I heard they were using an ABS product similar to what is used in geothermal that can withstand the shifting of the concrete which will happen and the joints are specially welded and pressure tested. My two cents worth.

there is a special anti-freeze for those boilers for floor heat. when the heat is shut down your good for a few days till it cools off. myself i dont like that type of heat one bit. its like your standing on a stove and your feet are always hot. i know turn it down but it is still not comfortable for me.its very good for melting frozen vehicles underneith though. i like the radiant htrs.depends on your preference and what the building is to be used for.also the temp setting needs time to adjust, not like a theremostat that is instant.

The tubeing is not copper. It is the recommemded type of tubeing for floor heat. When the building isn't going to be used for 2 or3 months, we are wondering if we can turn the heat off without any problems. Chris

Seeing that it is a group of people involved in this project, what is said here is not really going to matter that much . For the final answer that will be accepted to all, I would call the manufacture of the tubing.

I myself say the tubing will be fine if not heated.

I would never use in floor heat where it would be turned off and on.

It will take longer to warm the building for just a short time of use. Forced air heat will warm it faster. Not saying it will take more energy just longer to get the temp up for a evening meeting.

I would never allow the building to freeze, for fear of heaving in the floor. You may have to heat all the time.

Lastly extreme heating and cooling may cause the floor to crack sooner.

I'm sorry super99 somehow I got copper out of that, it's been a long day! I stand corrected.

Rapid heating and cooling tends to cause more stress and therefore cracks.Particularly around the freezing point.
Type of heater doesn't matter particularly energy wise. The demand unit takes up less space and responds faster.

Hey Super 99,
I've got it in my barn and love it! Your standing in the heat, so you don't have to turn it up very high. I leave mine set at around 52-53 degrees.
From lots of years in the concrete and excavating business, I agree with IA Gary.If you let it freeze too hard in the building, the floor slab is liable to heave and could play hell with the tubing.
My Son has been looking into a system that uses organic stuff (grass, horse poop, etc to create heat in a rotating drum that looks promising. Still need the gas for back up, but the cheap stuff will be your primary fuel.
I'll get the address and get back to you.
Larry NE IL.

My car washes have tubing in the floor ,we have a 400,000 btu boiler for heat . Unit is mainly just to keep ice off bay floors ,but there is no cracking in exstream cold like we are having now. and we just use 50-50 green anti freeze in our system no problem and it's all 8 years old

If you use a demand heater you can't use glycol. You can't get an efficient enough heat transfer. I just started up my system. Rannai heater in a 30X48' well insulated shop. It took 4 days for the concrete temperature to equalize. Started at 50 degrees F. to 77 degrees, stat. set at 65. VERY comfortable to work in, but used a huge amount of propane to get it stable.

I have 30 gallons of water in my system. The rannai puts out a constant 104 degrees forever if needed. I couldn't imagine using a 30 gallon water heater.

As everyone said, in-floor hot water heat isn't a great choice for building that you don't need to keep heated. But if you did the job right, it should not matter whether or not the pipes are filled. If you did the job wrong, filling the pipes won't prevent cracking, anyway.

You should have cut control joints in the pad if it's very large. And the pipe underneath the joints should have been covered with some sort of tubing to allow a bit of movement between the slabs. Whether or not you need control joints depends on the size and thickness of the slab, I don't recall what the rule is.

I work at a Raspberry farm and we have a large cold storage building that runs at -10 degrees all year long, when they built the building they put in tubing to heat the floor. It runs anti-freeze through it to heat it. I was told they put it in to prevent cracking becasue of the cold temperatures. It's a different situation but I could see how the heating and cooling of the concrete could damage the floor. Maybe you should talk to a company that deals with alot of infloor heating systems and get their opinion on it.

Several posters have pointed out that there is no "instant" warm up with in-floor heating.

If I wasn't going to keep the heat on, I'd certainly use some type of anti-freeze in the tubing. My worry, without anti-freeze, would be expansion of the tubing when it froze. I think it would pop up the concrete over the tubing, much like a rebar rusting in a bridge deck.

My son built a 30X50 shop with hot water in-floor heat. It was nice - he used an electric boiler that looked suspiciously like an electric water heater. No anti-freeze, but we're in southern Illinois. He set the thermostat on the lowest setting and left it alone.

I worked with a guy who bought a house with in-floor hot water heat. Concrete floors, nice modern gas boiler. He was a tightwad, and waited 'til it got to 40 degrees before he turned the heat on. Took three days steady burning to get the house warmed up. Lotsa mass in that conc floor. Probably didn't save much money.

Paul

My sister just put up a 50x 80 building . in floor heat . PEX tubing is used , glycol mixture is a must . They use an electic boiler . I have seen tank type water heaters used with no problems . It is not very fast to respond to temp adjustments, takes few days . I think you 'd want something faster if it is not heated all the time . Forced air might be good option

Don't forget that if you do go with in-floor, and WANT a "fast" warmup boost, you can also get fan-coil units and incorporporate into the same system. These are basically just a huge heater like in your car---a heat exchanger with water/ glycol, and a fan, hooked with appropriate valving and pump into the boiler setup

Around here, most guys put the PEX tubing in the SAND beneath the concrete so the cracks in the concrete that inevitably occur won't break the tubing.

I don't suppose anyone ever suggested that to you guys?

Bob,

Why would you want to heat the dirt under the building? It gets expensive. It's best to have insulation under the slab. A little more money up front, but a huge cost savings over time.

Built a 50'X48' building with 6" slab, and in-floor heat, and supplemental forced air furnace, with Plastic "zip strips" in floor for stress cracking. I use straight water in system, as Glycol mixture reduces heat transfer to concrete dramatically, resulting in a bigger boiler being needed. You NEVER CUT or DRILL into finished floor with tubing in floor. If you are only going to "ocasionally" heat building to comfortable Temps., then you will want a glycol mixture in system. You will have to turn heat on at least 2-3 days ahead of time. I would recommend running floor heat w/o glycol, at min. temp all winter, and adding supplemental forced air units for quicker recovery for comfortable temps when needed.

Bob, I've never saw the PEX placed beneath the concrete around here - not saying you're wrong, but I see no need to heat the sand/soil/gravel beneath the floor. We have only done two floors, so no expert. We compacted the CA-6 real good with a heavy turtle, spread out visquine, laid one inch blue board, fabric sheets on white brick, then zip-tied the PEX to the pavement fabric. Chairs don't do too good on the foam board unless you use sand plates, so bricks were our choice. No joints in the entire floor - both floors 30X50. The "no joints" concept goes against everything I've ever done in a lifetime in concrete. Both floors - no visible cracks - but I know they're there. All floors crack. It seems that the PEX is very forgiving and would stand a certain amount of cracking on a firmly compacted subgrade. If it gets kinked, you can carefully pass a propane torch over it and it will "heal" itself. Best way to avoid kinking/laydown problems with the PEX is to use a modified high tensile fence wire spinner. We chose the heavier pavement fabric sheets over the thinner roll mesh, and also made a greater than normal effort on the subgrade compaction in hopes of no vertical slab movement. We're very happy with the finished product.

Bob, I have a feeling you already know all of this and more. Just describing how we did it in our area.

Best wishes,
Paul