Hydronic Radiant Floor Heat
For Concrete Slabs

Hydronic radiant floor heat is one of the most efficient ways to warm your garage or home that is on a concrete slab. Hydronic floor heating uses hot water that is pumped through tubing in the slab. The concrete absorbs the heat from the water, and then radiates warmth to people and objects in the room. Radiant heated floors are also one of the most comfortable ways to heat a garage or a home.

Although hydronic floor heating can be used with other types of flooring, the concrete slab is where it really stands out. Concrete has a high thermal mass, and is able to store a tremendous amount of heat. Once the concrete is warmed up, it will slowly expel that heat for quite some time before needing to be reheated again.

There are three basic types of hydronic radiant floor heat systems. First is the open system, which shares the same water heater that is used for your home or garage. This system is the most economical, because you only have to have one heat source (water heater). It would not be the best choice for a detached garage that does not have its own hot water, because of the danger of the water freezing and the distance the water has to travel from your home to the garage.

The second type of hydronic floor heating unit is the closed system. This system uses a water heater that is dedicated to the radiant floor system. The water in a closed system is re-circulated around in a closed loop, and it never mixes with water that is used for any other purposes. It is not connected to a water supply.

The main advantage is that you can use an antifreeze mixture in the system since it is not used for anything else. This type of hydronic radiant heating system is commonly found in buildings that are not occupied for lengths of time that would allow the slab to cool down to the point of freezing. A closed system is also a good idea in areas that experience long power outages.

The disadvantage to a closed system with antifreeze is that antifreeze is roughly 15% less efficient at transferring heat than water is. You also will have to have a separate water heater for your bathroom and kitchen. A single high-efficiency water heater is more economical in the long run.

The third type of hydronic radiant floor heat is the heat exchanger system. This system uses a heat exchanger to separate the regular water from the antifreeze mixture that is used in the floor. You can have only one heat source, and still use antifreeze in the hydronic floor heating system. If you have a vacation home or a garage that is not used for several days or even weeks at a time in the winter, this type of system is a viable solution. You can drain the regular water system and the antifreeze will keep the radiant heating system from freezing.

The disadvantage of a heat exchanger system is that the exchanger is not 100% efficient. Some heat is lost to the air during the process. Yes, this lost heat will be escaping into the building you are heating, but the escaped heat could have gone into the floor with an open or closed system.

You can use any type of water heater for a hydronic radiant heating system, but you have to make sure it is big enough for the application. If you have an open system, you need to verify that it can supply enough hot water for the floor and for your regular bath and kitchen needs. Solar water heaters are particularly well suited for a hydronic radiant heating system. The heated water from the solar collector will store heat in the concrete slab during the day, and then the heat is released through the floor at night.

Hydronic radiant floor heat is the most popular type of radiant heat flooring for use with a concrete slab. If you are building a new garage or home on a slab, installing radiant floor heat tubing may be a good idea, even if you are not planning on using a radiant floor heater right away. It is a whole lot cheaper and easier to do it ahead of time than to add it later.

One disadvantage to any type of hydronic radiant heating system is the initial cost. The components and installation are much more expensive up front than a typical electric or gas heater that you will find in a garage. However, the system will pay for itself (and more) in the long run by saving money on your energy bills if you use the heating system very much.

For information on other heating alternatives, explore our Related Pages menu on the right near the top of this page. Visit our Radiant Floor Heating System page for more information on the benefits of radiant floor systems in general. You might also want to take a look at electric radiant floor heat. However, hydronic radiant floor heat will cost less than electric in the long run.

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