Installing Carpet
Over Heated Floors
The advantages
of energy efficiency combined with a distinctly comfortable heat
source have made heated floors increasingly popular in many parts
of the country. Often referred to as hydronic or "radiant-heated"
floors, these floor systems have been popular in Europe for many
years. Most systems utilize low-temperature water of about 80°
F to 125° F flowing through flexible tubing installed beneath
the floors. These systems can be embedded in concrete slabs, lightweight
overpours or in joist cavities.
Floor
Covering Considerations
With a floor heating system, the entire floor works as a giant
radiator. The comfort benefits are immediately obvious under tile,
marble, vinyl and wood flooring; however, radiant floor heating
works equally well under carpeting. With installations involving
carpet and cushion, consideration must be given to the thermal
resistance rating (R-value) of the carpet and padding.
Manufacturers
of heated floor systems state that less thermally conductive floors,
such as those covered with thick carpets, particularly with heavy
cushions beneath, may require the use of hotter water. This may
preclude the use of water-to-water geothermal heat pumps, some
solar systems, and some waste heat recovery systems. Regardless,
most homeowners accept some efficiency reduction so that the additional
benefits offered by carpet will be enjoyed. A not-so-obvious benefit
which should be recognized is that carpet tends to shorten the
heating season by providing a "foot warm" floor rather than a
"foot cold" floor as with hard surface floorings.
Heated floor
system efficiency can be improved by properly selecting carpet
and carpet cushion. Most floor systems manufacturers suggest a
total maximum R-value for carpet and cushion not to exceed 4.0.
With heated floors, lower pile carpet is better than higher pile
carpet, and the absence of cushion is preferred.
When cushion
is used, it should be no thicker than 3/8". Cushions specifically
designed for heated floor use are available and should be considered.
Call the Carpet Cushion Council at 203-637-1312 for additional
information on cushion selection.
