What is “R&Q” flooring?

Q: We are looking to install wood flooring over radiant heat. The term “R&Q flooring” has come up. What does this mean? Are we limited to engineered wood flooring?

A: Rift and Quarter sawn is more of a vertical angle with the grain rather than plain or flat sawn and is more stable in side to side movement than plain sawn. It is also more expensive because less of it can be cut from a log. Here is an article regarding radiant heat from woodfloorsonline.com.