Under Floor heating system; do you have experience installing / finding an expert on the korean system?

I dont know about the Korean system, it seems a little "old school" but the way you do it now is with water tubes circulating hot water under your floor. Basically, the floor can be any material, but concrete will work best as the tubes can be totally encased. However, you can use a standard flooring like wood floor and just use some type of radiant barrier on the underside of the radiant heating tubes to direct the heat upward into the wood.