Buildings have a large thermal capacity and it affects much on building thermal load for the HVAC system. The thermal mass can be utilized also to control the thermal load by storing thermal energy before HVAC operation. There are two ways to store thermal energy. One is by operating the HVAC system and the other is by natural ventilation, mainly at night. The latter could be combined with daily HVAC operation as a hybrid ventilation. Thermal mass storage is useful to decrease the hourly peak load and the daily thermal load and can be used for both cooling and heating purpose. Several applications of HVAC systems with thermal mass storage are presented and its effects on indoor environment and thermal loads are discussed.