Concrete slabs not only provide a durable and decorative interior flooring surface, they can also serve as a giant radiant heat source. Called hydronic heating systems, radiant-heated floors employ embedded tubing in concrete and circulate warm water throughout the building. Radiant heat from the floor develops a more comfortable heating profile for the occupants than forced-air heat. In-slab hydronic heaters heat from the floor up, providing heat to the living space rather than the air towards the ceiling. Because the heat profile is more efficient, thermostats can be set lower to save energy costs. Hydronic heaters are thus more comfortable and more efficient.
Installation of these systems is relatively simple. Elastomeric, plastic, or copper tubes are distributed along the subgrade or elevated slab form. Insulation is provided to the edges of the slab and footing – an important step to reduce the heat loss. The tubing layout is secured and concrete can be poured. The heat source can be any boiler, water heater, or solar collector to provide a warm water source. Pumps and manifolds to exchange the circulated water are located in an accessible location. Most hydronic system manufacturers have computer programs to design the layout of the tubing system as well as for calculation of heat loss.
Concrete for these systems is essentially satisfied by building code requirements for strength and durability of the slab. As long as the tubing is protected during placement and a two inch clear cover of concrete is maintained, slab construction carried out as if no tubing were present. It is suggested that the tubes be charged with water during placement to avoid crushing. In addition, if metal tubing is used, maintaining separation between the tube and any metal reinforcement is necessary.
See more at Concrete Floors on Ground, EB075, or Radiant Heat with Concrete, "Concrete Technology Today." PCA, April 1997.