Radiant floor heating systems offer gradual, room-filling convection heat that is silent and relatively energy efficient. Yet due to the amount of heat generated by these systems' electric wires or hydronic tubes, not all floor coverings can be installed over them. Still, radiant floor heating can be installed under a surprisingly large number of floor coverings. Properties that make a floor covering good or bad for radiant heating systems tend to center around the thickness of the flooring and the flooring's thermal conductive nature. Thicker floor coverings like solid hardwood and engineered wood are poor thermal bridges. Mineral-based floor coverings, chiefly tile and stone, are excellent thermal conductors.
Porcelain or Ceramic Tile
Porcelain and ceramic tile are practically made for radiant floor heating systems. Not only is tile thin but its mineral-based nature means that it conducts heat well. Additionally, since tile contains no organic products, it will not rot or degrade if a hydronic system leaks water. Tile heats up rapidly as soon as the system turns on. Tile, too, retains heat for a short while after the system shuts off.
Natural Stone Flooring
Similar to ceramic and porcelain tile, any kind of natural stone or aggregate stone is a natural fit for radiant heating systems. Not only is stone safe to use over radiant heating, it retains heat for a longer period than tile after system shut-off.
Laminate flooring's thinness is an asset when installing radiant heating, allowing the heat to penetrate and dissipate. Precautions must be taken to protect the flooring, though. In hydronic systems, should moisture escape, the laminate would be permanently damaged. The temperature of the system must be kept below the maximum point that is recommended by the laminate flooring manufacturer. Many laminate flooring manufacturers recommend that the temperature should never exceed 85 degrees F.
Sheet or Tile Vinyl Flooring
Radiant heating can be installed under resilient flooring such as sheet vinyl, tile vinyl, and luxury vinyl plank. Check the manufacturer's installation instructions for maximum temperatures. Generally, begin with 70 degrees F during the first 24 hours of use, increasing to no more than 85 degrees F.
Engineered Wood Flooring
Between solid hardwood and engineered wood flooring, the latter is recommended as a better candidate for radiant heating systems. Engineered wood flooring employs high-quality plywood as a base for its top layer of hardwood veneer. This type of plywood is dimensionally stable and does not quickly respond to temperature spikes or drops. However, wood is a poor thermal conductor. This means that heat from the system will not transmit as quickly or as thoroughly as with thinner floors that are more thermally conductive.
Due to the excellent insulating properties of carpeting, radiant heating systems will experience efficiency reduction and thus may require that the thermostat is turned up higher than it would be with hard flooring. But adding radiant heating under carpeting may be redundant. According to a study conducted by the Georgia Institute of Technology School of Textile Engineering, carpeting alone can reach R-values as high as 2.46 for plush wool. When combined with a bonded polyurethane padding (R-value of 2.09), carpeting may be warm enough alone that radiant heating is not even required.
Solid Hardwood Flooring
While engineered wood flooring works better, if you wish to install radiant heat under solid hardwood, use quarter-sawn wood flooring instead of plain-sawn wood flooring. The heating element should be embedded within a sleeper system subfloor, under a traditional subfloor, or embedded within concrete. Narrower floor boards tend to work better than wide-plank because the multiplicity of seams allows for more flexibility if the floor should expand and contract. Extremely dense hardwoods that rank 1,375 or more on the Janka hardness scale are a poor fit for radiant heating systems.
Floors That Should Not Have Radiant Heat Flooring
- Rubber flooring does not react well to high heat and may give off unpleasant odors.
- Radiant heating can dry and loosen adhesive on glued-down carpeting. In fact, any type of flooring that employs adhesive as its joining system is a poorer choice for radiant heating systems than flooring that uses tongue-and-groove or fold-and-lock seaming.
- Since concrete flooring is homogeneous, concrete alone is a poor choice for radiant heating. Radiant systems require layered flooring so that the tubing can be hidden under the top layer. However, radiant heat systems can be embedded in concrete floor slabs, as long as a subsequent top floor covering such as tile is added.