Due to lacking of natural resources, the major energy utilized in Taiwan are mostly imported, including oil (50.9%), Coal (32.3%), and natural gas (8.1%), nuclear (7.3%) and hydraulic power (1.4%). Therefore, energy saving strategies have become a global trend and needs immediate action so that CO2 emission can be reduced. To coup with the Kyoto protocol, building energy conservation has been deemed as a policy of no regret and aiming at 20% savings in the whole nation. In this research, building energy conservation strategies, especially on HVAC systems which have been widely adapted in Taiwan will be analyzed and validated with full-scale experimental results. Efforts will be especially focused on commercial and residential buildings, so that their energy savings effect can be analyzed quantitatively.