Abstract: Door constructions are provided including a frame, a core, and on both the inner and outer faces of the core an iron plate at least 0.2 millimeters thick with a wooden layer adhesively secured to the outer surfaces thereof. Preferably the core provided is a material having superior heat insulating properties with a heat conductivity of between about 0.15 and 0.05 as well as a diffusion resistance at least 20 times greater than that of air. In a preferred embodiment, each of the iron plates has a wooden layer adhesively secured to both the inner and outer surfaces thereof.