Radiant Floor Heating for a Small Shop

Shop owners who have tried it recommend radiant floor heating, and offer tips for a good installation. April 24, 2006

I am just breaking ground on a 36 x 40 cabinet shop on my property at home. Sounds small in relation to full blown shops but I'm a small one man band and loving it. My question relates to heating the shop itself. Since this is new construction I have the chance now to put radiant heat in the concrete floor before we pour. Although I've done plenty of homework comparing radiant heat to conventional forced air and the like, I haven't found anyone who has had experience with it in a shop situation.

Some of my reasons for considering radiant: the heat might not come quick but it's more consistent; it's a moist heat so I lessen the shrinkage problems of a dry shop, and without the blowers from forced air I don't have dust blowing around nor do I have to worry about static electricity. The boiler will be in the house with feed lines underground to the shop so I don't need a furnace room, (no flame to make the lacquer go boom), and the best part, my feet stay warm.

So these among some other things make this seem like a no-brainer. What am I missing? Has anyone had any experiences either way?

Forum Responses
(Business and Management Forum)
From contributor A:
The radiant flooring will be the best thing you ever did. The second would be consideration on where the dust collection lines run. Some like it overhead, and some, if they had the chance, would put it the ground. I am no authority on it but if you have a shop layout for equipment you could easily determine what you need for DC lines. Also electrical is to be considered here. There will be many opinions out there but if you know the shop layout, it would help in the decision making.

From contributor B:
Go for the radiant, you'll love it. If you're using a boiler type system, is there a possibility of using a steam modine type heater? You may not want it, but some people like the feel of warm air.

From contributor C:

Check out the Radiant Floor Company's website. They are an excellent company to deal with. The most efficient way to heat most buildings is using radiant floor transmission. The first supply source is a gas powered super-efficient hot water heater. The second supply source is roof mounted solar hot water collectors. The government usually has tax credits or loan programs for solar systems especially on commercial buildings. The new solar systems are very efficient and long-lasting.

Radiant Floor supplies all this stuff. Give them a call and they will layout, and quote a system for you in a couple of days. They sort of specialize in DIY projects. Fine Homebuilding did a test house issue 2 years ago that proved the radiant/hot water heater/solar system is the best.

From contributor D:
No question – in-floor heat is the way to go. I have a 40 X 64 pole barn in Michigan. I got all mine online at Radiantech, or something like that. I faxed them a layout of how I wanted the zones set up and they did the rest. I had about $10 of parts left over and about 30 ft. of tubing. They were good! I use the hot water heater, natural gas. The system complete was about $5000.00, but I think a great long term investment. There are a lot of other things to consider when putting this system in - the good news is you’re heading in the right direction.

From contributor E:
In floor is the way to go. If you do go that route you will want to set it where it is comfortable and leave it. As you posted it is not instant heat - you can not turn it up at the beginning of the day and turn it down when you leave. Make sure you put down 2 inches of closed cell foam or you will lose all your heat to the ground. They make staples to fasten directly to the foam. This method works best when no wire is used in the concrete. If no wire is used you have to use fiber crete. The stuff with the fiber is better any way.

I have a 40 x 102 floor that was done in 1 pour with no expansion joints, 3 years ago, and it has no cracks yet. I also have a floor that is 36 x 48 one pour with wire in it, no fiber, and cracks everywhere.

From contributor F:
There is no such thing as "moist heat" unless you pour water on the floor! The process of raising the temperature of the air lowers the relative humidity. If you want to maintain proper relative humidity while heating the air you need to add moisture to the air. The charts can be found in the ASHRE manual, check it out at your library.

From the original questioner:
Thank you guys for your input on the radiant heat. That's what I needed in order to decide which way to go. I never thought about DC in the floor as well. That's an interesting option as well. I have to do some homework on that fiber crete. My mason never mentioned that type of bedding beneath the slab. The plan was to attach the radiant tubing right to the wire mesh. Thanks again guys for your help.

From contributor F:
One thing I'd do is make sure you have a way of isolating individual tubes in case one springs a leak.

From contributor G:
I have it in my shop and it is the only way. You can set the thermostat on 60 degrees and it is very comfortable. Make sure you use a blanket that is used for radiant floor heating, so it reflects the heat up. It is similar to a concrete blanket.

From contributor H:
To contributor E: What's the price difference, if any, between fiber crete and concrete? Is it poured the same thickness? What about footings?

From contributor E:
It was about 3 years ago when I did my floor, and I think it was around 12 to 15 dollars a yard more. I thought well worth the extra cost. No wire to deal with! Yes it gets poured the same thickness. As far as footings go I think you still have to use rebar. It all boils down to what the local codes allow.

From contributor I:
Wish I had this information when I was building my shop. What about weight on floor-like a 25,000 lb router? Will that work with the pad and stuff?

From the original questioner:
As far as isolating loops in case of leakage I thought of laying out the loops a little differently than the typical design they show in their brochures. From what I've read, all the heat loops branch off of a central manifold. They radiate out and return back for a maximum run of 250 LF. Every sample layout I've see is a residential layout where the individual loops are designated for one room, maybe lapping over into an adjacent room, so here you've broken the house up into sections and looped each one individually. I tried laying out the shop area similarly but, as you questioned, what if one loop fails? I'm imbedded in concrete, I can kiss that loop goodbye and that leaves me with a cold section somewhere in the floor. I thought instead of sections for the loops I'd take several loops together and lay them side by side through the floor, so if one fails I have its neighbors picking up the difference.

To contributor G: The RH blanket you refer to, is it like a thin heat shield? My mason will insulate the perimeter foundation walls with Styrofoam boards before pouring the floor in order to keep the heat from radiating out from under the foundation. The question about doing the same for the slab also came up for the same reason you present. Two of the guys disagreed. One said "Do it", and the other said the Styrofoam was not stable enough to take the weight and could crack down the road. Both scenarios make sense so tell me more about the blanket you refer to. It sounds like the best solution.

From contributor E:
The foam under the floor is more critical than the foam around the perimeter. What you need is a higher R value below the floor than the floor itself. The law of physics says heat seeks cold and it will take the easiest path to get there, the path of least resistance. Water transfers heat more rapidly than air, so if the ground below your slab is wet or the water table is high and you have no (or not enough) R value, your heat will go to the ground not the slab. As far as a tube getting a leak, forget it - it won't happen, unless someone puts a nail or screw in it. It is very strong well tested stuff. Be sure and use he-pex as it has an oxygen barrier that regular pex does not. This is critical if your heat source has any iron in it.

I was in the heating business for many years before going to the cabinet business. I have installed hundreds if not thousands of in floor heat systems. I have seen in-floor heat systems not work because the contractor did not want to spend the money on the foam.
The type of carpet pad on top of the floor is even critical as to whether it will work or not. Anyway, put down the foam (higher R than the slab and any flooring) - it may cost you a little more at first but you will notice it in your heat bill one way or the other.

From the original questioner:
I've finally seen some "in slab" examples on some of the web sites that were mentioned in this forum. I've requested help with layout and costs from two of them so we'll see what they come up with. I 'll share the results with the forum as I get them. Thanks for your input. With your experience I'll definitely keep you up to speed as I move forward.

One more question. Concern has been brought up again about possible deflection and cracking in the floor from the weight of the equipment or vibration if foam board is placed in below the concrete as an insulator. Again these are my mason's concerns. The foam board that I use, though, is it a dense foam unlike that which you'd use against the walls?

From contributor E:
The foam is very dense, usually pink or blue. It is closed cell not like the white Styrofoam. It is very hard to crush and you can walk on it with out it denting. As far as weight goes as long as your ground is good and level (and compacted) you should be able to set any large machines on it with out a problem as long as the slab is at least 4" thick. I have a 5 x 10 Anderson router, auto beam saw and many other heavy machines on my floor with out any problems.