Abstract: A heat radiating board and a method for cooling by utilizing the same based on a novel principle of heat gradient. The heat radiating board, which is disposed between a high temperature zone and a low temperature zone, consists of a metal plate and a heat gradient-forming layer laminated on the surface thereof facing the low temperature zone, this heat gradient-forming layer being formed from a heat conductive material having a heat volume and an absorption of heat of radiation smaller than the metal plate.

Abstract: A heat insulating board and a method for heat insulation by utilizing the same based on a novel heat-insulation theory utilizing a heat gradient. And, this heat insulating board is characterized by consisting of a composite body of an opaque heat-conducting base body positioned to face the low temperature zone and a heat conductive transparent layer positioned to face the high temperature zone, the said transparent layer having a heat volume and an absorption of heat of radiation smaller than the heat volume and absorption of heat of radiation of the said base body.

Abstract: Disclosed are a composite plastic film and a greenhouse constructed by using the same as a covering sheet spread over a framework capable of exhibiting improved temperature elevation-suppressing effect in summer and improved warm-keeping effect in winter. The composite film has a double-layered structure consisting of a transparent or translucent thermoplastic resin film as the substrate and a transparent overlayer of a polymeric resin formed on one surface of the substrate film and these two layers are correlated each with the other in relation to two newly defined parameters including "the total heat volume", which is a product of the overall weight and the specific heat capacity of the film, and "the absorptivity of radiation heat" defined in terms of the decrease in the radiation temperature of sunlight by transmitting the film, the overlayer having the total heat volume not exceeding 10% of that of the substrate film and the absorptivity of radiation heat not exceeding 60% of that of the substrate film.