After experiencing a floor-heated ‘Korean room’ in Tokyo in the 1910s (possibly in 1920), Frank Lloyd Wright (1867–1959) applied its operating principle to his Usonian houses, starting with the Jacobs House I (1936–7). Successively, Wright’s heating method, along with other Usonian features, was applied to many postwar mass-produced houses, particularly those by Levitt & Sons in New York and Eichler Homes in California, two representative housing development companies in mid-century America. In their tract housing projects undertaken for about two decades from the late 1940s, floor heating (what is generally called ‘radiant heating’) was attractive not only owing to its thermal comfort but also because its slab system without a basement made construction inexpensive and expeditious. Although research on Levitt and Eichler homes has often mentioned the new heating method in relation to Wright’s influence, they could hardly identify the inspiration that Wright drew from Korea. Bridging the gap, this study argues that the Korean floor-heating idea disseminated to postwar mass-produced houses in America through Wright. Considering that their affordable houses were targeted at ordinary families seeking the American dream in a renewed social context, it can be said that Korean heat warmed the American dream, albeit indirectly. Ultimately, this radiated Korean heat would illustrate how one culture influences another, resulting in cultural cross-fertilisation.