I am considering installing a heating system while designing a new house with some greener & cost efficient building materials. And I'm gathering info on people with some knowledge here before goggling on until my but is tired. Any help is dearly appreciated. Wikipedia... An Ondol, also called Gudeul, in Korean traditional architecture, is underfloor heating which utilizes direct heat transfer from wood smoke to the underside of a thick masonry floor. In modern usage it refers to any type of underfloor heating, or a hotel or sleeping room in Korean (as opposed to Western) style.