The proportional relationship between the infrared (IR) transmittance of a transparent material and its IR-induced heat transfer can be explained via a simple model. An agreement between the theory and the experimental work was examined by measuring the temperature rising inside a heat-insulated box with glass windows under IR irradiation, where the material of the glass windows was modified from corning glass (CG) to 9 at% Nb-doped TiO₂ (TNO) fabricated by sputtering deposition. The fabricated TNO thin film was mostly transparent in a visible region and had a low transparency in the IR region, which, in turn, produced the self-cooling effect inside the insulated box. In comparison to the window glass made by CG, the temperature increase inside the box would be 24% less if the window was made by CG coated by TNO (TNO on CG). This suggests the possibility of manufacturing products with desirable features in the energy-cut cooling. The energy-cut was found to decline proportionally to the decrease of the glass window area.