Shop radiant floor heat

zenmek · Nov 22, 2002

I'm considering putting in a radiant heat floor system (concrete pad) in a future shop i'd like to build. I plan on insulating walls to R-19 and ceiling to a R-25~30 and use blue board under the pad. The heat will be supplied from a domestic hot water heater (electric). Does anybody have a similar setup that I could compare heating costs with? I would probably keep the temperature at about 60 degrees F. Oh yeah the sq.ft. of shop is 960, and I live in central KY. Any info is greatly appreciated!

Anonymous Poster · Nov 23, 2002

there has been a lot of discussion of these systems on www.agriculture.com Shop Talk board.

DougM · Nov 23, 2002

http://www.radiantec.com/radman1f.pdf

I just purchased from here

I do not know if it Works yet as I have just poured the slab.

Doug

zenmek · Nov 23, 2002

Thanks for the replies. DougM, Radiantec is where I was looking also, Did they treat ya good? I would sure like to know how yours pans out.

ljh2 · Nov 23, 2002

I'm sure you've given it some thought, but one guy I know isn't real happy with his use of in-slab radiant heat for a shop/barn. If you are planning to maintain a constant warm environment, you could be happy with this arrangement, but in this guy's application, he intended to keep a moderate temperature when he wasn't working in the shop, and increase the temp when he was there.

-- The problem is that the large thermal mass of the slab floor doesn't respond quickly to temperature changes, so if you "turn up the heat", don't expect your environment to warm up very fast.

Good Luck!

TimSullivan · Nov 23, 2002

ljh2,

The in floor heat is wonderful but you are right about the slow warm up. Electric in our area would also be very expensive. Most people go with propane or natural gas.

rockyridgefarm · Nov 24, 2002

Size the system for the standby heat and use radient heat for the wuick warm up

rockyridgefarm · Nov 25, 2002

Electric water heat aint cheap!/w3tcompact/icons/shocked.gif

What I would do is use some passive solar features in the design. Basicly make sure there is plenty of south facing glass where the low winter sun can heat that slab. Use overhangs or decidous trees to shade them in the summer. There are lots of sources for diagrams to size them properly, as well as, the proper placement of shading. It wouldn't add very much to the cost of the shop, and could do most of your heating.

zenmek · Nov 25, 2002

I like your idea of the passive solar heat, as far as the water heater, I'm lucky enough to live in an area that has one of the lowest rates in the country /w3tcompact/icons/grin.gif for electric! Thanks

heehaw · Nov 25, 2002

there is a shop about 10 miles from me that uses radiant floor heat, and it is great; they used the orange natural gas line in their floor, and tied it to a natural gas water heater. a pump is hooked to the thermostat, and when heat is needed, the pump kicks on. i was in the shop once when the outside temp was 10degrees F; and it was very comfortable.
heehaw

Hoeman00 · Nov 26, 2002

When I built my house addition (new basement under
1/2 of the 150yr old part too) I put 2" dow under floor and
used the orange PEP tubing tied to concrete mesh
before pouring the floor.
Did this in the attached garage 26' X 28' X 12' hi also.
I have an outside wood fired boiler w/ 3 zones,
1 for forced air heat in the 60 x 40 x 15' shop.
1 for forced air heat in house 4000+ sq. ft.
1 for the floor radiant heat.
To do floor radiant u need 1' of tubing/ 1 sq. ft. of floor.
The floor has 4 300' loops and garage has 2 300' loops
all hooked to same manifold (this lets me adjust temp
between the house and garage).
The warm floor is GREAT, feet feel good when standing
or laying on it when working.
Use one of the digital thermastats that u can set
different times and temps (when working in morning
set it to start heating at 4 am. or so).
This is VERY efficient heat and w/ my basement
set at 72*(garage is 75*) u sweat when working.
I would recommend 60* range for general working
in t shirt.

AndyR · Nov 26, 2002

Did you add air transfer coils to your existing furnaces when you went to the outside boiler? I am thinking of much the same setup - but hopefully with a few solar hot water panels so I don't have to fire the boiler on cool days.

MossRoad · Nov 26, 2002

We had a heated floor where I use to work. It used about 600 gallons of kerosene every month! But it was an airplane hangar /w3tcompact/icons/laugh.gif/w3tcompact/icons/laugh.gif/w3tcompact/icons/laugh.gif BIG building.

That floor was so nice to work on. You could pull in a wet sloppy snowy vehicle at night and by morning everything was melted off and evaporated off the floor. You would have to lay on cardboard to keep from sweating. If you had a puddle on the floor, you could squeegee it out and it would dry in 5 minutes. And if you had to open the doors and let all the heat out, as soon as you closed the doors it would get warm again. Just about instantly.

The downside was, it took a day to get it going from a stop. No instant heat there. We had some type of ethylene glycol mixture in it so it wouldn't freeze.

I plan on heating our next house this way. There are so many ways to generate hot water that I won't be tied to one fuel source either.

Good luck.

DougM · Nov 26, 2002

Could some one Post pictures of how every thing is
Plumbed ??/

would help me a lot

Doug

boustany · Nov 26, 2002

Make sure, make real, real sure, that 6 mil or so plastic is laid over the foam insulation before the concrete is poured. Otherwise, you'll see cracking like you've never seen before, on acount of the concrete stick to the foam like you wouldn't believe, so as it contracts, it cracks. And make sure they use reinforcong mesh (i.e. 6" grid) which keeps the cracks down too, and gives you something to attach the PEX to.
My house/basement is radient. Works swell, but I'm not sure I'd use in it a shop unless I was planning on living in it. It can take a day or more to heat a slab to temperature, so you'll have to maintain heat even when you are not using it.
I designed/installed my complete system. Happy to help anybody who is interested.

Hoeman00 · Nov 27, 2002

Yes I added a coil to the shop and in process
of adding one to the house now that we have
the new ductwork run.
Only problem is the heat exchanger in the
furnace is cracked so for heat, until I can
find an exchanger, the hot water coil is
setting in the old kitchen and a fan blowing
across it

Boy the old kitchen is HOT

JEP · Nov 27, 2002

I can give you a cost reference. My neighbor has a 60' X 120' barn with 14' ceilings. Half of it is insulated and heated so 3600 sq. ft. He keeps the floor temperature at 70 F and it cost him $600 the first year. Not bad I thought. He has a oil boiler at ~$1.30 per gallon or about 460 gallons. The insulation is similar to what you are using, maybe a little better. This is in Southern Michigan where is gets below 0 F at least a few times a year.

Someone else can check my conversion or technique:
The BTU value of on gallon #2 Fuel oil 137199 BTU
BTU to kWh one gallon oil is 40.2 kWh
Multiple by 80% efficient hot water heater 32.1 kWh
Multiply by 460 gallons is 14788 kWh per year
Multiply by $.05 per kWh (don't know what you mean by cheap electricity, you can multiply by your local cost) $740 a year electric.

Again this is for a building that is almost 4 times the size of yours and a little colder climate.

JEP

zenmek · Nov 28, 2002

Thanks for that post, it was very informative. As far as your formula, it sounds good to me! Our electric (All electric residential rate) is currently $0.043 per Kwh, so That would translate to a very affordable option.

Rch · Nov 30, 2002

<A target="_blank" HREF=http://www.jlconline.com/cgi-bin/jlconline.storefront/3de933580076b6e0271a401e1d290643/Product/View/9811usin>http://www.jlconline.com/cgi-bin/jlconline.storefront/3de933580076b6e0271a401e1d290643/Product/View/9811usin</A>
Good reference for hot water tank radiant heat. Note the author !