Abstract: Heat-mirror coatings are important as transparent insulation for a host of applications, including building window glazings. They reduce thermal emittance of glass and polymeric substrates, thereby decreasing the effective radiative loss of a glazing or window assembly. Properties of coatings and substrates, as well as various window designs, are detailed. The paper reviews heat-mirror deposition technology including chemical vapor deposition using hydrolysis and pyrolysis reactions, dc and rf sputtering using reactive, biased and nonreactive techniques, vapor deposition and ion plating. The properties of single-layer films including coatings of In 2 O 3 :Sn, doped SnO 2 , Cd 2 SnO 4 , noble and transition metal films are enumerated. Multilayer films described include dielectric overcoated metals such as ZnS/metal/ZnS, Bi 2 O 3 /Au/Bi 2 O 3 and TiO 2 /Ag/TiO 2 . Electrical, solar and infrared radiative properties are tabulated. Much of the data presented is also useful for photovoltaic and collector applications. New and innovative materials systems are suggested.