If you're importing a tropical or exotic wood, you must pay close attention to the source and age of the wood as well as the method used in drying it. Quick drying creates stresses that can affect the wood later as it expands and contracts.
Which hardwood floors work best? Extensive laboratory testing by Launstein Hardwood Floors in Mason, Mich., found that American hardwoods - including cherry, oak, ash, maple, hickory and walnut - are good choices for radiant-heat flooring.
For best results, use narrow boards, preferably not wider than 3 inches. Narrow boards will better accommodate wood's expansion and contraction across a floor.
Consider using quarter-sawn wood for planks wider than 3 inches, regardless of species, for enhanced dimensional stability.
The Launstein testing found that quarter-sawn planks up to 7 inches across (when properly installed) can work well with radiant heat systems.
The testing also found that hardwood flooring that is three-eighths of an inch thick conducts heat better than thicker floors and resists gapping.