Hydronic Floors & Hot Water Heat

[dadster4]

I've installed over 30 in-floor systems- gravel, poly vapor barrier, 2" high density foam board, 6" mesh, fasten oxygen -barrier PEX 12" O.C. to the mesh with zip ties. Concrete guys will pull the mesh up 2" from top of pour as they work. You can use a water heater for a heat source for such a small area (remove the anode rod). Tekmar makes a thermostat that uses air temp AND slab temp- install slab sensor in conduit before the pour.

 

[ovrszd]

I've installed over 30 in-floor systems- gravel, poly vapor barrier, 2" high density foam board, 6" mesh, fasten oxygen -barrier PEX 12" O.C. to the mesh with zip ties. Concrete guys will pull the mesh up 2" from top of pour as they work. You can use a water heater for a heat source for such a small area (remove the anode rod). Tekmar makes a thermostat that uses air temp AND slab temp- install slab sensor in conduit before the pour.

Good stuff.

 

[teejk]

I've installed over 30 in-floor systems- gravel, poly vapor barrier, 2" high density foam board, 6" mesh, fasten oxygen -barrier PEX 12" O.C. to the mesh with zip ties. Concrete guys will pull the mesh up 2" from top of pour as they work. You can use a water heater for a heat source for such a small area (remove the anode rod). Tekmar makes a thermostat that uses air temp AND slab temp- install slab sensor in conduit before the pour.

That's exactly what we did back in 2010 other than ours is a traditional wall mounted thermostat/relay/circulating pump. The current thinking now might have switched to an "on-demand" boiler in place of the water heater. In either event it is essentially a closed loop system. Depending on climate you might want to consider glycol anti-freeze to a 50/50 blend. Zip ties instead of staples allows the tubing/mesh to be pulled up during the pour as you mentioned. The concrete guy may insist that you nip the ends of the zip ties to make sure they don't protrude up through the slab. It needs to be mentioned that there are limits to the distance of the loops (depends on the diameter of the tubing). I heat 1,200 sq ft so I think we had 3 loops that all return to a manifold (5/8" tubing...1/2" would have shorter loops). We used Rehau brand tubing and the lengths are marked on the tubing. I would recommend renting an uncoiler rather than having to man-handle the coil.

 

[rScotty]

Check out Supplyhouse.com. great price. Free shipping.

Gravel base. Plastic covered. Pinkboard. PEX pipe. Steel. Then pour concrete.

I recommend 2" pinkboard insulation. Lay the PEX on the pinkboard and staple it down. Supply house has the staples. They also have the elbow sleeves to protect the PEX where it comes thru the concrete.

Problem with doing a small area is you still need the heater, expansion tank, pumps, manifold with valves. Makes the cost per square foot pretty high.

We just finished pouring a 1875 square foot shop floor. When operationall it will have a cost of $2.80 per square foot.

Yes it will be high per square foot. Your price seems exceptionally good. Mine won't even be close to that nice $$/sq. ft figure.
Of course not being so large the total price isn't all that bad. The heater is the big expense. I'll use an regular HWH to heat the fluid, and even so the HWH alone will probably cost as much or more than the rest of hydronic system.

 

[CalG]

I didn't insulate the "thin slab", its up above grade, on sandy fill, about 2 feet.

The "on grade", "immersed pipes in slab" (if that is a term) is over 2 inch "blue board".

I can not detect any difference when the heat is not on, summer or winter. (summer time to dry the sweat). The thin slab without insulation is by far the "faster" system. Less mass I suppose.

Both give comfort without heating the surroundings,

 

[Paddy]

rScotty,

our home is heated radiant. It's great. But I would not use it in a shop unless you were in it 16 hrs a day. Radiant has a very slow response time. So best set the temp and leave it, but expensive to heat a large space 24 hrs a day. I would think a shop heat would be shut off when not in use.

 

[teejk]

rScotty,

our home is heated radiant. It's great. But I would not use it in a shop unless you were in it 16 hrs a day. Radiant has a very slow response time. So best set the temp and leave it, but expensive to heat a large space 24 hrs a day. I would think a shop heat would be shut off when not in use.

I figure 3 days or so to totally ramp up from a cold start in my shop. But there is something in the brain that says if your feet/legs are warm your whole body feels warm. It's a trade-off. As noted earlier, I think the trend is away from water heaters towards "on-demand" units. You could manually drop the temperature a few degrees when the shop isn't used. Recovering a few degrees doesn't take that long.

 

[rScotty]

I figure 3 days or so to totally ramp up from a cold start in my shop. But there is something in the brain that says if your feet/legs are warm your whole body feels warm. It's a trade-off. As noted earlier, I think the trend is away from water heaters towards "on-demand" units. You could manually drop the temperature a few degrees when the shop isn't used. Recovering a few degrees doesn't take that long.

In our home I use a small propane heater or wood stove on cold winter days. The hydronic heat simply provides a baseline of heat year round - especially for when we go away for winter vacations. I'm thinking the same thing will apply for the shop. My shop typically has shelves of things like paint, caulk, tubes of silicone & sealer - all things that are better if kept from really cold temps.
rScotty

 

[teejk]

In our home I use a small propane heater or wood stove on cold winter days. The hydronic heat simply provides a baseline of heat year round - especially for when we go away for winter vacations. I'm thinking the same thing will apply for the shop. My shop typically has shelves of things like paint, caulk, tubes of silicone & sealer - all things that are better if kept from really cold temps.
rScotty

Your latter point is true. I killed an expensive pressure washer in my shop because our LP supplier forgot to fill the tank (I have 2, both on "keep-full"...they got the house but not the shop).

 

[rScotty]

I didn't insulate the "thin slab", its up above grade, on sandy fill, about 2 feet.

The "on grade", "immersed pipes in slab" (if that is a term) is over 2 inch "blue board".

I can not detect any difference when the heat is not on, summer or winter. (summer time to dry the sweat). The thin slab without insulation is by far the "faster" system. Less mass I suppose.

Both give comfort without heating the surroundings,

Cal, when you did the thin pour how did you hold the pipes down to the slab substrate? How is it built?
thanks,