Transparent heat mirror which allows the transmission of visible sunlight while reflects the infrared thermal energy is an effective building energy efficiency technology for hot climatic regions. In this work, a five-layer dielectric/metal/dielectric/metal/dielectric (DMDMD) coating of Si3N4/Ag/Si3N4/Ag/Si3N4 structure is proposed. The radiative properties of the five-layer coatings are theoretically investigated by transfer matrix method. The thicknesses of the layers are optimized by using particle swarm optimization method. The sample of the designed Si3N4/Ag/Si3N4/Ag/Si3N4 coating is prepared and the building energy performance when applying the DMDMD coating in a simple office room is also investigated, taking the hot weather condition of Guangzhou, China as an example. The simulated results show that the Tave + Rave value of the five-layer coating is 8% higher than that of the three-layer coating, and the long-wave emittance of the five-layer coating is 24.8% lower than that of the three-layer coating. And the application of the five-layer coatings on the glazed window could provide the highest energy saving rate of 8.9% when compared with the traditional low-e coatings.