Direct gain passive solar heating systems need a balance of three elements: 1) the incorporation of sufficient solar radiation from windows, 2) the storage of heat by an appropriate material, and 3) the reduction of heat loss by insulation. In recent years, inexpensive and comfortable solar heating using direct gain and heat storage has become more feasible. This is due to advancements in high thermal insulation as a result of energy-saving standards. Latent heat storage material (Phase Change Material, PCM) is being developed and promoted because it has a stabilizing effect on room temperature and has been attracting attention in recent years as a heat storage material. Because no evaluation method has yet been established, it is necessary to analyze the characteristics of PCM. In this study, we proposed direct gain passive solar heating systems distributing the indoor solar radiation using additional material installed on the windows (NIR film). These systems store solar radiation in a wide area quickly by having PCM installed in not the only floor, but also the ceiling. Some analysis of charging and discharging PCM heat behavior were carried out to study the effects on reducing the heating load in a direct gain solar heating house by actual measurement and simulation. The results are summarized as follows:
- Through the measurement, it was confirmed that the combination of PCM, NIR film and low resistance ceiling caused stabilization effect on room temperature. The measurement showed that using NIR film reduced the rise of daytime room temperature by about 1.1°C and the fall of nighttime temperature by about 0.7°C (Case3). Furthermore, by using low resistance ceiling, overheating in the daytime was reduced by about 0.9°C (Case4).
- Simulation model with solar radiation distribution and latent heat storage (PCM) was proposed, and the accuracy of the simulation model was confirmed by comparing experimental results with calculated results.
