What is radiant heat?
Radiant heat is actually a very old technology that is used both indoors and outdoors. The Romans were among the first to build systems based on this premise by building special rooms over concrete slabs and brick ductwork. Hot air or steam from fires built beneath these structures circulated up through the system thereby radiating heat into the room above.
The two most common types of under floor radiant heating systems are electric or hydronic (hot water). The electric system usually consists of a matt of heating elements placed under the floor while the hydronic system uses a series of tubes connected to a hot water boiler. Both systems produce heat that radiates upward into the room.
How will a wood floor behave over radiant heat?
The most important factor in a successful wood flooring installation over radiant heat is proper acclimation of the wood flooring and the surrounding materials. The slab, plywood subfloor and/or joists should be acclimated to within 3-4% of each other. This can be accomplished by turning on the radiant heat system before installing the wood floor. If this isn’t done properly, moisture left in the slab will enter the wood flooring as soon as the heat is turned on. Depending on the stability of the wood, there can be undesirable results such as greater expansion and contraction, or even checking or cupping. All interested parties should be educated on why this process is important to avoid any consequences after installation.
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 a preferred time of five to six days. That assumes that the slab has been in 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 wood floors. As always, follow the recommendations of your wood flooring manufacturer.
All of Mountain Lumber’s floors can be installed over radiant heat. Our floors are incredibly stable, much more stable than most freshly-cut timbers. Our engineered EntiqueTM floor, with the added structure of its multi-directional ply backing works exceptionally well over radiant heat.
Radiant heating technology has evolved over the years and the water in hydronic systems now runs at cooler temperatures than it did years ago, ranging from 90 degrees to 140 degrees. In years past, when water temperatures exceeded 140 degrees, wood fibers were repeatedly traumatized, causing stress fractures, gaps and twisting. Repeated heating and cooling also broke down any adhesive used to bond the hardwood to the slab.
But today, thermostat controls can help avoid those problems and added humidity controls help manage the consistency in temperatures, alleviating the need to make adjustments throughout the season. Your thermostats will work in conjunction to gear up the system as colder weather approaches and help maintain a comfortable temperature inside the house – all the while preserving the quality of your wood floors.
Can you install antique wood over radiant heat?
Generally speaking, there is no doubt that radiant heat is the perfect type of heating system with wood flooring, including reclaimed antique, for several reasons:
- Wood is an excellent conductor of heat, meaning that heat is able to easily travel through the material into the surrounding space.
- Wood is an effective distributor of heat. Combined with radiant heat systems, the warm air is distributed evenly in all directions throughout the room, as opposed to forced hot air or baseboard systems which direct the heat to rise. This explains why radiant heat is also an efficient system with wood flooring: A large area of mild surface temperatures, such as a warm floor, is capable of transferring a significant amount of heat throughout a room or home.
- Wood is a wonderful retainer of heat. It will naturally hold on to the warmth even if the heating system temperature drops or is turned off. This also contributes to the efficiency of the heating system as it does not have to work as hard to keep the room warm.
Radiant heat is healthier for the wood than alternative heating systems. The heat is evenly distributed throughout the floor at a low temperature, so each board is exposed to the same amount of heat and does not encounter uneven drying- such as is the case with baseboard or forced hot air where there is a concentration of warm air along the edges of the room or in certain areas of the floor; this can cause variations in moisture content and uneven expansion and contraction.
Radiant heating actually replicates the natural process that antique wood has experienced. Wood that was used to support a building, factory or barn was exposed for decades to a regular increase and decrease in temperature and moisture. In some cases, the timbers from which the boards were cut have been slightly expanding and contracting for over a century in their previous installation. Radiant heat, with its low temperatures and even distribution affects the wood flooring the same way, but the impact is much less dramatic with antique wood than newly sawn wood because it has already been through this cycle for years!
- Includes references from NWFA technical publication No. A100
Please call us with your questions and comments. We will be happy to assist you with more information and help you select the right floor for your situation.
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