Ever heard of electric radiant floor heat under slab? - Contractor Talk - Professional Construction and Remodeling Forum

IHI · 02-25-2009, 11:45 PM

Getting pieces in place to throw up a garage here at home and it will have radiant floor heat, and i had planned the traditional route with PEX, but a freind of mine i race with said a buddy of his installed some sort electric radiant floor heat under his slab in his 30x40 shop, and says it's the only way to go since there's nothing to go bad.

I guess they installed seperate 200amp service to this building so it's considered all electric since the house is on propane, and supposedly his utilites to heat the shop are next to nothing. For me, i'm in town and hooked to NG so i cant get an "all electric" price break unless i did the same, which i dont intent to do and dont even know if they allow the electricity price reduction since it's on the same property as my house hooked to NG.

So- anybody heard of this stuff? How's it priced compared to typical water heat? How effeicent is it? Obviously i have'nt googled it yet since i was hoping for first hand expereince..just trying to get things organized and in place before the ground thaws.

olyteddy · 02-26-2009, 11:55 AM

Years ago in TN I used to come across a product known as 'Ceil Heat'. It was radiant electric heat embedded in the ceiling drywall. Don't see why there wouldn't be a similar product for floors.

MALCO.New.York · 02-26-2009, 12:21 PM

They are often used in Walkways and Driveways in Cold, Precipitous areas of the Country.

NuHeat etcetera.

kbsparky · 02-26-2009, 09:52 PM

IN-floor electric radiant heating is available out there, but be warned, this stuff can go bad.

We did a job recently in a bathroom tile floor which went "bad" after about a year. The thermostat's built-in GFCI started tripping, and there really is not a way to repair those element wires once embedded into the concrete/tile.

We worked around the problem by installing an isolation transformer on the heating elements. This solution prevented us from having to bust up the floor, and replace the whole she-bang. At least for now ....

IHI · 02-26-2009, 10:02 PM

Google has provided me with nothing that sounds close to what this guy has in his shop. supposedly it's BIG electric cable encased in some sort of sheathing to protect it from the cement and drying temps, i guess it's big stuff, like 6ga cable size and it gets laid in just like PEX water lines would...i dunno? never heard of it, cant find anything online about it to investigate, so i'm sticking with putting water through the floor instead of electricity.

I may run another circuit out 10' under ground and up into the new shed location too so i can have a seperate storage area able to be kept above freezing as well since the main system is already plumbed no too far away anyhow.

SLSTech · 02-26-2009, 10:08 PM

How much does it cost to run? It may be cheaper up front, but I am willing to bet it will cost you big time on the electric bill.

cleveman · 02-26-2009, 10:10 PM

it's probably cost effective as long as you have a reactor close by.

Come to think of it, that is a good way to think of it. If a guy asks if electric heat is efficient, just tell him that you can stay warm with it as you stoke coal into the generator to produce the electricity to run through wires to produce heat. The only thing better is when you plug a car into the electricity, or an electric powered coal mine.

IHI · 02-26-2009, 10:28 PM

Quote:

Originally Posted by SLSTech

How much does it cost to run? It may be cheaper up front, but I am willing to bet it will cost you big time on the electric bill.

If my property was 100% electric i could see whatever system he's talking about being more effeicent than say a boiler set up since you get a huuuuge price reduction for being all electric, freinds of ours utuilites average on total 12 $70-90/month that are all electric while ours hovers around $150/month and then spikes like a mofo during the winter whereas theirs stays more constant.

The building will be insulated well enough i'm sure a ceramic heater would fir the bill too, but since i work on vehicles i want a warm slab, there is no other option

granted with the hoist i wont be wallowing around on the ground like we've all done growing up, but i wont have it any other way.

SLSTech · 02-26-2009, 10:33 PM

Screw the boiler - its just a shop, go with a water heater set to 110 degrees

Fine Homebuilding (?) just had a good article on all the different types of Radiant Floor systems (electric floor wasn't one of them though) which discussed the pros & cons of WH, Boilers & type of systems.

MALCO.New.York · 02-27-2009, 04:21 AM

AllWarm.Com

Warmsmeallup · 02-27-2009, 05:32 PM

Yes, you can insert a low voltage or line voltage element in the slab just before pouring the concrete. If you are looking for a primary heating system, a heat loss calc is mandatory.

KBSparky: Yes, the line voltage cables/mats are VERY difficult to fix, but they can be in the right circumstances. Though we won't install them (for just that reason) we have fixed many. Not fixed more than many though

I can go into a long explanation of what makes them difficult but there's no need here as it doesn't change the fact.

IHI:
If you choose to go electric, insert a low voltage element. It attaches right to a remesh held 1-1/2" from the surface. DON'T forget the insulation below the pour. IF you have any problems with it, a simple tic tracer will find the break and a butt splice with some heat shrink fixes it. However, the installation design almost all but prevents the issues from arising.

Any electric system will be just about 100% efficient (+/- .03%) in that any electricity you buy generates heat without any substantial loss between the source and the floor. You also won't have to pay for maintenance and it won't cost you anything unless it's calling for heat. Once you do the heat loss, come back a post the results along with what you pay per kilowatt hour for electricity and I can tell how much it will cost to run.