Electric Radiant Floor Heat,
Is It Right For You
Electric radiant floor heat uses electrical cables or mats to warm the floor and provide radiant heat. Since this website is about garages, I will focus primarily on cables buried in a concrete slab. Most of the principles here will apply to homes built on a slab and other flooring systems as well.
Radiant floor heat has a lot of advantages over forced air or other types of systems. The warmth comes from the floor up and warms the objects in a room, instead of heating the air. Warm air naturally rises to the ceiling where it is largely wasted. Because of this, radiant heated floors are generally more efficient than forced air. With radiant heat, you also don't have dust and other contaminants being blown around like you do with forced air.
Electric radiant floor heat is silent, clean, and requires no maintenance. If your floor has a large thermal mass (such as a concrete slab), once warmed up it will slowly radiate warmth for hours without much added input. If the utility company in your area offers discounted off-peak rates, you can warm the floor all night when the rates are lower, and the concrete will expel its warmth throughout the day when electric rates are higher.
However, a large thermal mass takes longer to warm up, too. If you let the concrete cool off too much, it will take several hours for it to warm up again. Most experts recommend that you maintain the floor temperature within a relatively small range with a radiant floor heating system.
As stated earlier, electric radiant floor heat can use either cables or mats to supply the warmth to the floor. Cables are generally attached to the concrete reinforcement (such as wire mesh) and buried inside the slab. They can be installed on top of the slab by adding a layer of thinset concrete after the cable is laid out.
Mats are usually used on top of the slab but underneath a floor covering such as tile, wood or vinyl. Mats can get by with a thinner layer of thinset concrete than cables on top of the slab can. The cable is less expensive to purchase than mats, but the mats are quicker and easier to install.
To get the maximum efficiency out of an electric in floor heating system, the slab should be insulated underneath and on the edges. Radiant heat travels in all directions, and if the slab is not insulated, the ground underneath and around it will absorb a great deal of the heat. Some folks argue that this is a good thing, because then you have a larger "heat reservoir" to draw from.
The reality is that if the heat is not "contained" by insulation, the warmth will continue to be wicked away by the ground, and you will end up with a large semi-heated area around and underneath your garage (or home). This can actually be an advantage in areas that experience long power outages, because it will take longer for the floor to cool down when the power goes off. The drawback is that you are actually heating a HUGE area all the time, and this runs up your power bill on a continual basis.
For heating relatively small areas, an electric system is more economical than hydronic system which uses hot water pumped through tubing. For a garage sized area (or a home built on a slab), a hydronic radiant heating system will usually be more economical in the long run, but electric in floor heating still has a few advantages. It is easier to install than a hydronic system, and you don't have to worry about water leaks. The up-front cost of an electric in floor heating system is also much lower than a hydronic system.
Just to give you something to think about, here are some numbers: The current (2013) average cost of electricity in the US is about 12 cents per kilowatt hour. One kilowatt = 1000 watts. Rates vary widely by state, so check your power bill to determine your current rate. Electric radiant floor heat systems use an average of about 12 watts per square foot.
12 watts x 12 cents = $1.44/1000kw = roughly $0.0144 per square foot her hour. For a 1000 square foot area, it will cost about $1.44 per hour that the electric in floor heating system is turned on. Your actual cost will vary depending on your electric rate, insulation, outdoor temperature, etc.
One thing to consider when looking at electric radiant floor systems is EMF radiation. Studies have shown that long term exposure to high levels of EMF radiation increases the risk of cancer and other diseases. EMF radiation comes from almost anything that uses electricity.
Some electric radiant floor heating systems utilize a "twisted pair" type of wire that minimizes the EMF radiation. The two wires cancel each other out. Some people believe that the whole "EMF radiation" thing is nonsense and is just media hype, but better safe than sorry! I would spend a little more and get a system that uses the twisted pair type of cable.
To find out more about the benefits of in floor radiant heat, visit my Radiant Floor Heating page. For more information on different types of heaters, go to our Related Pages menu on the right near the top of this page.
The bottom line is that if you are building a garage or house on a slab and can afford it, a hydronic radiant floor heating system is probably your best bet in the long run. However, for a smaller area or if you are adding radiant heat flooring on an existing slab, then electric radiant floor heat may be the way to go.
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