Radiant Heat: A Warm House from the Floor Up
If a new house or a room addition is something that's in your future, you may be thinking about what type of heating system to install. One system that may not come to mind - but that's well worth considering - is radiant floor heat.
A typical radiant floor heating system consists of a series of tubes set in a bed of lightweight concrete or other similar material, then covered by any standard floor covering. Hot water is circulated through the tubing, which warms the bedding material and radiates heat up from the floor to warm the entire house.
Radiant floor heating has a number of advantages. There are no heat registers in the floor or heaters in the wall to restrict the placement of furniture and window coverings. Since there is no airflow forcing the heat into the rooms, there are no drafts or unpleasant air currents, and wall and ceiling surfaces stay cleaner. Radiant floor heat is silent, and there are no filters to clean.
On the down side, this is a heat-only system - if you want central air conditioning you'll still have to install a duct system. And since room air does not circulate through the system as it does with a forced air system, you can't add optional, whole-house accessories such as an electronic air cleaner or a humidifier.
How it Works
At the heart of the system is a boiler unit that heats the water, typically located in the garage or utility area. For cost efficiency, most installations utilize natural gas for the boiler if it's available in the home. Other fuel options, as with any furnace system, include oil- and propane-fired boilers, as well as electric.
From the boiler, the heated water is pushed by a small recirculating pump through the tubing in the floor. The tubing is separated into zones, which, depending on the size of the area, may be a single room or a series of rooms. A manifold system, typically located in an accessible wall cavity, provides a series of simple valves that are used to regulate the flow of water through each zone. The tubing is a closed loop, so after the water gives off its heat to the room, it returns to the boiler for reheating and recirculation.
Radiant floor heat is installed over standard joist and subfloor construction. Joist spacing may need to be decreased to provide additional structural support for the weight of the bedding material. The joists and subfloor are installed in the usual manner, then the subfloor is covered with a layer of plastic sheeting to keep it from absorbing moisture when the wet bedding material is installed.
Next, 2x4 or 2x6 "sleepers" are installed on top of the subfloor wherever there will be an interior or exterior wall. The plastic tubing is then laid out in a continuous loop pattern starting from the control manifold, and is secured to the subfloor with special fasteners. Once all of the tubing has been installed, a pressure test is performed on the system using compressed air to ensure that there are no leaks in any of the tubes or fittings.
The final step is the installation of the bedding material, which may be lightweight concrete, a gypsum and cement mixture, or other material. The mixture is applied as a semi-liquid - thinner than normal concrete - so that it flows easily and levels itself out. It is typically poured 1 1/2 inches thick, so that it ends up level with the top of the 2x wall sleepers. Interior walls are framed and covered as usual, then the floors can be covered with carpet, vinyl, hardwood, ceramic tile, or any other standard floor covering.
When considering a radiant floor heating system, look for a contractor who specializes in this type of installation. This is definitely not a do-it-yourself project, and should be left to a company who has verifiable experience with these systems.
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