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Hardwood Floors & Radiant Heat

Wood floors with a radiant heating system underfoot can be a wonderful amenity for any home or office. If you are considering a radiant heating system with your hardwood flooring there are several aspects, which should be taken into, considered before you make your final choice of both wood and heating system.

Hot Water Pipe Systems

The most prevalent type of radiant heat system used today is the hot water pipe system, which is run in the same way as your central heating system. Usually the pipes will be laid in a concrete screed composed of a lightweight concrete, although they can be run between joists with metal dispersion plates. This lightweight concrete should be poured at a 3000 psi in order for the wood floors to be glued directly.

When installing a wood floor on top a radiant heat system within a concrete screed, the floors should not be installed until the relative humidity of the concrete has reached 75% or below. The only way to test for this is:

(a) by drilling into the screed and inserting plastic plugs, then returning after 24 hours to take readings
(b) by use of a humidity box

Once this level of relative humidity has been reached, and the radiant heat system has been fully tested and has been running for two weeks, then – and only then –at that time the wood flooring be acclimatized to its environment. Acclimation must take place with the radiant heat system running and with the surface temperature of the sub floor not to exceed 80 degrees Fahrenheit. For the sub floor surface temperature not to exceed 80 degrees Fahrenheit, the hot water in the pipes under the floor must be cooled at the manifold accordingly. It is crucial to get this calibration correct, in order to avoid damaging the floor in the future.

Engineered wood floors are recommended for their stability over hot water pipe radiant heating systems, and for the very best results we strongly recommend that the floor be glued down using an Polymer adhesive.

For two specific reasons: first, you will get a much better heat transfer when the floor is glued directly to the light weight concrete (putting down a plastic membrane followed by an underlay and then the floor will be like layers of blankets on a bed and will trap the heat under the floor); second, by fully bonding the floor to the concrete you are minimizing any possibility of movement, which will always be greater in a floor installed over radiant heat. We do not recommend using Maple, Pine, Hickory or Brazilian Cherry because they are noted to be unstable wood species.

Before installing the wood floors the under floor heating system must be turned down to the desired installation temperature of 65°F. On completion of the installation the under floor heating system must be left running at the installation temperature for a minimum of four days to allow the adhesive to fully cure at its optimal temperature. At the end of this four day period the heating can then be increased at increments of no more than 2°F each day until the desired temperature is reached, keeping in mind that the surface temperature of the floor should never exceed 80°F.

Whenever the heating is to be turned up or down in the future, it must always be done in increments of +/- 2°F per day to avoid undue stress on the floor as it adjusts to the new temperature. Always use specialists to install a hardwood floor with radiant heating. Our last suggestion is that you consider investing in a humidification/de-humidification system that will work in unison with your central heat and air system. Not only is maintaining the relative humidity levels between 35% and 55% optimal for ones health, it is also the ideal range for your wood floors. Making for a more stable environment and less movement in your wood floors through the seasons. Neglecting proper relative humidity levels with a radiant heat system can be devastating for hardwood floors. Please click on the following link for more information regarding these humidity control systems.