Floor heating or radiant floor heating was first noted 2000 years ago in Korea and and in Ancient Rome. It is the most efficient method of heating a home next to passive solar heat through windows.
Modern radiant floors come in many forms, from tubing in concrete slabs to tubing under wood floors that radiate heat both up and down. A general rule is that the more thermal mass (concrete, sand, or other heat absorbing substance) there is to hold the heat in the floor, and the closer that the tubes are spaced, the lower the water temperature needed to heat the area. In some cases we can heat a room with 25-28C water!
We need to put heat in all areas of a home. The first place to put it is in the basement. As there is a concrete slab in every basement the extra cost is only for tubing. The basement heat will radiate up heating the main floor, to some extent, as well. We have installed basement radiant floor heating and seen the energy required to heat the floor above reduced by as much as 75%.
The key to an efficient radiant system is low water temperatures and close tube spacing. However, a system designed for 28C water temperature will not work properly if one area has a need for more heat, such as a solarium. For rooms like these we will need supplemental heat if we cannot get enough from the floor. This can be added by hot water radiators, wall radiant, air handlers that provide forced air, fireplaces, etc.
In Europe, almost all floor heat is in cement as concrete construction is most common. In North America, where most floors are wood framed, we have a choice of methods for tube installation. Arguably, the most effective is to place the tubing in a lightweight cement (see the photo at right).
The tubing is stapled down to the plywood floor and the gypsum cement is poured like a milk shake. This gives a smooth surface for hardwoods, tile or marmoleum.