skip to main content

Heating & Air Conditioning

Electric Radiant heating on slab

12 years ago

Hi,

Our house is on a concrete slab and I want to understand the options for installing electric radiant heating on slab. I hear these have come a long way and there are ultra-thin mats available. Any advice on what to look out for, brands, sizing, any issues? Can we do room specific controls? We are thinking of doing tile or hardwood flooring. I searched the archives but could not find anything specific to my question.

We live in California near San Francisco, so not terribly cold but cold enough.

thanks

Lalitha

Sort by:Oldest

Comments (3)

david_cary
12 years ago
Electric radiant heating is generally used for small spaces like bathrooms. To do a larger area is a very expensive undertaking and even more expensive to use. The thought of doing that in CA is particularly insane....

Why insane? Well your peak rates are 4 times mine (maybe not but most of the Bay area is). and I wouldn't do it here because of the expense.

Makes far more sense to do hydronic and heat with NG. But any slab heating for a large area is really overkill in such a temperate climate. What do you heat your house currently with? Are you trying to heat your house with radiant heating (because that isn't really possible with electric) or are you just trying to take the chill off the floor?

Normally electric is used for taking the chill off of tile. Since you mentioned wood, I am guessing that you want to heat a room with this...
davidro1
12 years ago
i'd like to add a few points.

A slab is a thermal mass bigger than an elephant.
Concrete is a heat sink.
You do get all the heat back, if you own both sides of the slab.
In that case a concrete slab is a heat source as well. A governor.
Here you don't have that.
A slab on grade is connected to mother earth.
The more it acquires heat (from any source above), the more it loses heat to the ground underneath.
The more you try to heat it, the more you spend on heating the earth underneath.
That is a lot of mass.

This explains why seeds germinate next to rocks.
The rocks acquire heat from the sun and re-radiate that heat into the ground, triggering germination.

Your slab on grade might be on earth that is generally dry and warm. Or not.
The more moisture in the earth, the more slab heat is lost to the earth. More quickly.

It may be easy to have a warm floor on a warm slab on grade. Do nothing more than install wood on an underlayment.

It's difficult to turn a cold wet slab on grade into a warm floor.
A layer of really good insulation is required.
Now, you are walking on a raised floor.

Since you asked about the new and thin electric heating cables, I'll guess that you can't raise the floor by much.
Related Discussions
electric radiant heat under hardwood floors - recommendations?
Q
Comments (1)
The NWFA guidelines are a good place to start for advice on radiant heat under a wood floor. There is also a discussion on the link listed at the bottom. Hardwood Floors Magazine has a forum discussion at http://hardwoodfloorsmag.com/forum/topic165-solid-pine-over-radiant-heat.aspx. Launstein has a web page devoted to radiant heat at, http://www.launstein.com/radiant-heat/radiant-heat.html. American cherry and walnut are know to be more stable so are often suggested over radiant heat. There are a number of species that professionals have experienced problems with including Brazilian cherry. You might look at the discussion at http://hardwoodfloorsmag.com/forum/topic109-jatoba-over-radiant-heated-gypcrete.aspx Here is a link that might be useful: Blog on Radiant
...See More
Electric radiant floor heating - Sunctouch floor heat
Q
Comments (1)
There is no practical technology for passively shielding a heating element to virtually eliminate H-field EMF. The only effective approach is "active shielding". This means canceling the H-field of one heating element with the H-field of another parallel element. Watts Radiant electric heated floors use this approach with a complex wire made of two sets of heating element constructions; running them in parallel with a patented helical twist. Here is a link that might be useful: Electric Radiant Floor Heating
...See More
On-Slab Radiant Floor Heating Feasiblity
Q
Comments (2)
What you're proposing is certainly feasible using your existing boiler and some sort of 3 or 4 way mixing valve or assembly. Your floor would have to be isolated from the existing slab and you would not benefit from a thermal mass. However, you may have faster reaction times. Keep in mind that pipe spacing is related to water temperature so make sure of your design before starting and ordering materials. Do consult with a radiant in-floor specialist that understands hydronic boilers as well - you don't want surprises! SR
...See More
Radiant heat under laminate over concrete slab
Q
Comments (12)
True. There will be heat lost to the ground. Nonetheless, do not conclude there is no point at all in having a layer of insulation: any break is better than no break at all. Think of wearing one layer of light clothing as protection against the cold: better than bare skin. Any small R (e.g. R2, R3) still directs more heat upwards than not. To place radiant heat directly on the slab means more and more heat is lost as floor temperature rises, not just 50% but a far greater fraction. "thin" , "not very" , "useful" -- terms undefined. A separation layer is better than none. Not to overthink this, just to drum it in. "Something" is more than nothing, and this is the significant point, not whether the R factor appears low or high. Once your floor temperature rises, you want to prevent sending most of it into the ground, which is what happens when there is no insulation / isolation / separation at all. Note that the definition of R rating testing does not allow one to distinguish between heat transfer occurring by conduction or by radiation. In many circumstances this is not critical. If you want to get into this level of detail, it will take a few dense paragraphs. Suffice to say that R ratings will be misleading and inaccurate for this application so do not rely on the apparent differences between R numbers. They are all small and that is OK. They are almost meaningless in this situation of a slab-floor separator with a thickness of from 2 to 16 mm. It is obvious that with electric cables you have more room for a thicker insulation layer. HTH -david
...See More
davidro1
12 years ago
To get a warm house in the geographical area you are, think of making the house airtight with a housewrap, building it as they would in Alaska or the Yukon. Almost every house in the SF area feels cold in winter, and almost every house 1000 or 2000 miles farther north feels warm in winer.

Related Stories

FLOORS Is Radiant Heating or Cooling Right for You?

By Mariana Pickering (Emu Building Science)

Questions to ask before you go for one of these temperature systems in your floors or walls (yes, walls)

FLOORS Floors Warm Up to Radiant Heat

By Lindsey M. Roberts

Toasty toes and money saved are just two benefits of radiant heat under your concrete, wood or tile floors

GREAT HOME PROJECTS How to Add a Radiant Heat System

By Mariana Pickering (Emu Building Science)

Enjoy comfy, consistent temperatures and maybe even energy savings with hydronic heating and cooling

FLOORS What to Ask When Considering Heated Floors

By Toronto Interior Design Group

These questions can help you decide if radiant floor heating is right for you — and what your options are

BATHROOM DESIGN Warm Up Your Bathroom With Heated Floors

By Tiffany Carboni

If your bathroom floor is leaving you cold, try warming up to an electric heating system

GREEN BUILDING Insulation Basics: Heat, R-Value and the Building Envelope

By Mariana Pickering (Emu Building Science)

Learn how heat moves through a home and the materials that can stop it, to make sure your insulation is as effective as you think

REMODELING GUIDES Clean-Burning Woodstoves Ignite a Greener Heating Trend

By Laura Gaskill

No need to rely on oil or gas to heat your home — new woodstove designs burn cleanly and are beautiful to boot

HOUSEKEEPING 5 Steps to Improve Your Heating System Now

By Buckminster Green LLC

Increase your heater's efficiency and safety for lower energy bills and greater peace of mind this winter

GARDENING AND LANDSCAPING 3 Ways to Bring the Heat to Outdoor Living Spaces

By Matt Clawson

Here’s what to know about surviving winter’s bite with an outdoor fireplace, fire pit or heat lamp

GREEN BUILDING Houzz Tour: Passive House in Vermont Slashes Heating Bills

By Becky Harris

Its ecofriendly, low-maintenance design leaves a family with more time to relax and enjoy the weekend home

Sponsored

More Discussions

Mount range hood to wall or ceiling?

19

Cooling Mini Splits

65

A/c making humming sound

3

Typical charge to install fuse

17

humidifier for a furnace in a closet

0