Underfloor heating, also known as radiant heating, has been used in Europe for many years. This type of heating system is installed below the finish floor, usually during new construction or during a renovation. Underfloor heating works by warming the floor, which is different from traditional heating systems that heat a space. They are effective because heat rises and warms the room.
Underfloor heating has several advantages. First and foremost, it produces an even and constant heat. It is also quiet, easy to maintain, and more energy efficient. The air is cleaner than with forced hot air, and there is no need to use a humidifier to add moisture to the air. Another advantage of underfloor heating is that it frees up space in your home because there are no radiators or heating vents.
Hydronic and electric are the two types of underfloor heating systems most commonly used in homes. There is a third system that uses hot air, but it is seldom used.
Hydronic Underfloor Heating Systems
Hydronic systems use water to heat the floors and are imbedded in a concrete slab or in a thin layer of concrete over the sub-floor. Occasionally, they are suspended between the finish floor and the floor joists.
Most hydronic systems are closed heating systems, meaning that water is re-circulated through the system using a pump. Heated water moves from the boiler or water heater into the pipes that are located beneath the floor and is circulated around the house. Then it returns to the boiler or water heater to be reheated. Boilers are better for larger houses, while water heaters are best for heating small areas or smaller houses.
The pipes used to carry the heated water are attached to a manifold (similar to an electrical control panel), which is located near the boiler or water heater. Each pipe controls a zone in the house and has a shutoff valve that is used to control the flow of water circulating to each zone.
PEX tubing, made of an extremely durable polyethylene material, is now the most popular choice for underfloor heating pipes. In the past, copper pipes were used because of their excellent ability to transfer heat, but they fell out of favor because of their higher costs.
Typically a house is divided up into heating zones approximately 250 to 400 square feet in size, about the size of one room. Thermostats imbedded in the floor in each zone control the temperature of the water. Within each zone, pipes are laid out in a continuous loop using an S-shaped pattern.
Pipe spacing averages 12 inches. Spacing may be as close as 6 inches in areas that are heavily used, such as adjacent to kitchen counters or under a dining room table. In areas of low use, for example the middle of the floor, spacing is farther apart, up to a maximum of 18 inches.
Electric Underfloor Heating Systems
An electric underfloor heating system is much simpler than a hydronic one. It is most often used in kitchens or bathrooms and is an excellent way to heat laminate, stone, tile, and marble floors. It can be installed under existing floors or during new construction.
An electric underfloor heating system resembles a thin mat. It is constructed of thin electrical cables and enclosed by two sheets of a special fabric-like material, similar to an electric blanket.
The mat is imbedded in a thin layer of concrete and the cables are wired to an electrical circuit. The flooring material is then laid on top. The electric cables in the mat cables heat the floor, which radiates upward, heating the room. As with hydronic systems, the thermostat is imbedded in the floor.
