Radiant Floor Heating System, The Benefits of Radiant Floor Heat

A radiant floor heating system is perhaps the ultimate way to heat a garage, or any other structure that is built on a concrete slab. The system works by heating the concrete, which then radiates the warmth upwards to any objects (including people) in the room. Since it warms the objects and not just the air, you don’t lose all your heat when you open a garage door.

In floor radiant heat is efficient, silent, and doesn't blow dust around like forced air. It is safe for environments with flammable vapors (like a garage). It heats the room evenly, without any hot or cold areas. With radiant heat, people can be comfortable at temperatures that are several degrees cooler than with convection systems that heat the air instead.

With a radiant floor heating system, the air temperature is warmest at the floor, and gradually gets cooler as you go up. The slab itself is usually heated to a temperature of about 75 to 80 degrees. As you rise up to eye level, the air temp drops to roughly 68 degrees, and will be in the neighborhood of 60 degrees at the ceiling (8 ft.). A heated floor concentrates the warmth in the lower half of the room where the people are, instead of the warmest air being wasted at the ceiling like with a convection system.

Because of this, if you have a garage with a high ceiling, you can experience a big cost savings on your heating bill by using a radiant system. Even with a normal 8 foot ceiling height, you can expect to see roughly a 25% or so savings on your heating costs. One of the advantages of in floor radiant heat is that it does not promote the infiltration of cold air from outdoors like a forced air system does. Less heat is lost by cold air coming in through cracks or around windows.

There are two main types of radiant floor heating systems, electric and hydronic. Electric radiant floor heat uses electric cables or mats that are buried in the concrete. The up-front cost is generally lower than with a hydronic system, but the operating cost will likely be higher in the long run. Hydronic radiant floor heat uses hot water that is piped through the concrete. It will usually cost more to install than an electric system, but it is cheaper to operate, especially if you are heating a large area.

No matter which type of system you install, there are some things to consider. One reason that a radiant floor heating system is so effective in a concrete slab is that concrete has a high thermal mass. Once heated, concrete will radiate warmth for hours without any additional heat input.

Of course, the opposite side of that coin is that it takes several hours to warm up cold concrete. Most experts recommend maintaining a relatively constant temperature in the concrete for the system to be most efficient.

Another consideration is that the concrete will radiate heat both up and down. If the concrete is "on grade" like most garage slabs, the ground underneath the concrete can steal a great deal of the warmth. It is strongly recommended that one to two inches (or more) of high-density expanded polystyrene insulation be placed under the concrete slab and also around the edges of the slab. In floor radiant heat will be much more efficient if the concrete is insulated.

One disadvantage to in-floor heating systems is that they aren't practical for cooling also. If you live in an area where you also need air conditioning, you will have to install a separate system for that.

With all the advantages of an in-floor heating system, it is almost a no-brainer if you are building a new garage that will be used for several hours on a daily basis during cold weather. It may not be the best choice for a garage that is only used occasionally though, where you need quick heat for just a few hours. In that case you will probably be better off using an electric or gas garage heater. For more information on other types of heaters, take a look at our Related Pages menu on the right near the top of this page.

If you decide to go with radiant floor heat, make sure you insulate the slab and install a system with the correct capacity for your area and for the size of your garage (or home). You can't easily add capacity later, because the hydronic tubes (or cables/mats) are buried in the slab. If you want to do the installation yourself, many suppliers can help you make sure the system is sized correctly. Otherwise make sure you use a contractor that has experience installing radiant floor heating systems.

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