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Underfloor Radiant Heating

Heating any room with underfloor radiant heating is a possibility, but bathrooms and kitchens tend to be the most popular rooms. One reason is that tile and stone are popular flooring choices in those rooms and they tend to get chilly. Radiant floor heating is a good choice for heating chilly floors. It also has the advantage of efficiency because you can heat only occupied rooms instead of heating an entire home.

Underfloor heating can be installed under tile, stone, wood, laminate, concrete and in some cases, carpet. It is usually installed before the flooring is installed, but some products are available for retrofits into accessible joist bays beneath a floor.

There are two types of floor heating available, electric and circulated hot water. Both systems are regulated by a thermostat, just like other home heating systems, although this thermostat controls just a single room.

The electric style heating uses thin wire mesh mats or cables that are laid out over the subfloor and a reflective barrier and then are covered by another protective layer. The electrical usage is roughly 12 to 15 watts per square foot. For this reason, electric floor heat is usually limited to bathrooms and kitchens. Heating an entire home electrically could create a large electrical demand, possibly requiring an electrical upgrade for your home. Actual heating costs with electricity would have to be compared to alternative heating costs for the region where you live.

The circulating hot water system uses a system of tubing laid out in an array in a room and is then encased in a layer of concrete poured over the entire layout. The hot water can be supplied by a home's water heater system combined with a recirculating pump or additional water heating equipment may be added to support the radiant heating needs. Hot water radiant heating can be a viable system for heating an entire home.

When calculating the material requirements, it is important to note that the heating should not be installed under cabinets or appliances. The heating should be installed only under the open flooring areas; essentially any place where your feet may go. It some cases, manufacturers recommend installation to exclude areas under furniture and objects that may block the heat and cause overheating.

Advantages and Disadvantages to Underfloor Heating

Advantages of both electric and hot water underfloor heat:

  • Very low maintenance
  • Invisible to the eye
  • Reduces the movement of dust vs: forced air systems
  • Improved efficiency by heating only occupied rooms
  • Even and stable heat
  • Heats from the floor up vs filling a room with hot air from the top down
  • Water has the advantage of being suitable for heating an entire home
  • Electricity has the advantage of being easier and less expensive to install

Disadvantages of both electric and hot water radiant underfloor heat:

  • Service and repair may require removing some or all of the finished floor
  • Time to heat a room may be somewhat longer. Although, once operating, it can maintain a stable temperature economically
  • Not effective under insulating materials like thick carpet with cushion padding
  • Both systems can be damaged by careless workers during construction
  • With electric heat, if a wire breaks or fails, a section or entire floor system may stop heating. Pinpointing the fault may be difficult and require removing the entire finished floor to effect repairs
  • With hot water, if a pipe leaks, the system will continue to operate, but the leak may permeate the concrete and damage finished flooring. Pinpointing a leak may be easier
  • The installation of a water system requires more than 1.5 inches height, which may be problematic in a remodel situation
  • Wood plank floors may be prone to movement or even damage resulting from the radiant heat (can be reduced with a floating installation)

Recommendations and Notes for Radiant Floor Heating:

Solid wood floors are more prone to damage because of dimensional changes resulting from the application of direct heat; especially very thick wood flooring. Also, some reports suggest cherry and maple are more susceptible to damage.

There are indications that narrow planks are less susceptible than wide wood plank flooring.

Engineered wood flooring and quarter-sawn solid wood flooring are resistant to dimensional changes and so are better choices for wood flooring.

It is always best to work with a contractor who has experience installing a particular product. Try to choose builder who has worked with the product you choose or one who will subcontract the work to an experienced installer.

Don't put solid furniture or any object that can act as an insulator (like large floor pillows) over a radiant floor as it can lead to overheating.

The subfloor must be thoroughly dry before the installation of radiant floor heat. Otherwise, moisture will be trapped by the insulating material and cause damage.

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