Reclaimed Wood Over Radiant Heat Back to list

Radiant heating does not heat air directly as do more conventional forms of heating, such as baseboard convectors or forced air circulation.  Radiant heat is “Omni Directional.”  Unlike warm air, which tends to rise, radiant energy tends to travel in all directions.  A large area of mild surface temperatures, such as a warm floor, is capable of transferring as much heat as a small surface area, such as a steam radiator, at high surface temperatures. 

 

Radiant heat beneath reclaimed antique flooring involves tubing in concrete, or tubing under plywood subfloors.  The most important factor in a successful antique reclaimed wood installation over radiant heat is a dry slab and a dry subfloor.  The only sure way to dry a slab and a subfloor system is to turn on the radiant heating system before installing the antique reclaimed wood flooring.  If this isn’t done, moisture left in the slab will enter the wood flooring as soon as the heat is turned on.  The result is floors that will expand, contract, shrink, cup and bow excessively.  If the heat can’t be turned on then everyone involved – down to the homeowner—should understand and accept the compromises that will appear down the road. 

                 

Opinions on the amount of time required vary widely.  Some say the heating system should be turned on at least 72 hours before installation, with the preferred time of five to six days.  That assumes that the slab has been place for at least 60 days.  If the slab is relatively new, the recommendation is to have the heating system turned on for 30 to 60 days before installing antique reclaimed wood floors.

                 

Antique Reclaimed wood dries rapidly when the heat is first turned on.  It dries to a lower moisture content toward the end of the heating season.  When the radiant heat is turned off, moisture once again starts to seep into the wood subfloor and radiant slab.  Abruptly turning on the radiant heat in the fall will subject the antique reclaimed wood flooring to rapid and noticeable movement:  Evidence of this movement will be cupping or crowning of the reclaimed wood boards.  Finally, shrinkage cracks will appear between individual reclaimed floor boards.  Alternatively, gradually turning the heat on before the first really cool day will begin the seasonal movement more gradually.  Thus the movement of the floor will be much less noticeable.  As always, humidity controls can help offset flooring expansion and contraction.

                 

Not all species of antique reclaimed wood flooring are good candidates for an installation over radiant heating.  When possible choose a species of reclaimed wood, such as antique reclaimed Heart Pine, that is known for its stability.  Additionally, quartersawn or rift-sawn reclaimed antique flooring is preferable to plainsawn in the search for stability.  Reclaimed Antique wood strip flooring may also be a better choice than plank reclaimed flooring, because narrow boards expand and contract less than reclaimed wide plank flooring does.

 

Source:

 

National Wood Flooring Association Technical Publication No.  A100 “Wood flooring over Radiant Heat”, 1996