AbstractDetailed calculations have shown that radiation heat losses through double‐pane windows can be substantially reduced by the application of a thin, transparent film, reflective to long‐wave radiation (‘heat mirror’). The comparative analysis of different types of ‘heat mirror’ has been carried out, and a tin oxide layer deposited by spray has been recognized as the most suitable for large‐scale production.A tin oxide film has been deposited on glass by a spray method using ordinary commercial materials for the substrate, the solvent and the solution. The optical properties of the tin oxide films obtained have been compared with those measured on films deposited by more sophisticated methods; results are as follows: in comparison with vacuum‐deposited metallic films or vacuum‐deposited SnOx, films, our sprayed SnOx, films have similar or better transmissivity for visible spectra and somewhat (10–30 per cent) lower reflectivity for the infrared portion of the spectrum, but at the same time the prices of material and/or production costs are several orders