The theme of building energy conservation emphasizes not only on saving energy, but also on the comfort and safety of the theraml environment. In other words, it provides energy-saving function under the percussion of providing a safe, healthy, and comfortable thermal environment. This paper based its argument on the theory of the solar radiation. This paper identified the external factors that influence the solar radiation in relation to the natural movements of the Sun and Earth. It used computer programs to identify the location of each city and the position of the Sun at any given time. It also simulated the situation under which the shadow of the building changed, and analyzed the effect of the sun-blocking facilities of the building on indoor lighting. Furthermore, the author of this paper composed the sun radiation chart of Kaoshiung area to test the accuracy of the full-scale sun radiation experiment at NSYSU Lab. The accuracy of the experiment reached over 98%, which served as an important foundation for the calculation of the ENVLOAD value. Moreover, based on the computer simulation of the energy consumption on building envelope , this paper not only provided the ENVLOAD value, but also the evaluation of the sensitivity of the energy consumption on building envelope. Finally, this paper served as an important base for the ENVLOAD value of one specific building (Building N) in mid-Taiwan. The experiment on Building N found that the installation of horizontal external sunshades and light-gray blinds as internal sunshades saved 42% energy than the traditional curtain wall buildings. This result further demonstrated of the energy savings effect experimentally. Base on systematic analysis and full-scale experiments, this paper proposed the best energy saving model for Building N under the weather condition at Taichung. This model not only satisfied our current legislation for energy saving construction, but also provided a thermal comfortable environment. This paper contributes greatly to the field of building energy conservation design. Furthermore, this study was carried out under the local weather condition of Taiwan, which contributed significantly as a criteria for further regulation and modification of the ENVOLOAD value in Taiwan in the future.