Rating system for energy and energy-related performance of fenestration is determined by the Thermal Transmittance(U-factor) and Solar Heat Gain Coefficient(SHGC). The U-factor is a concept of the heat transfer induced by unit temperature difference between the environments on each side of a fenestration system, and the SHGC is a concept of the ratio of solar heat gain through the fenestration system per unit area to solar radiation incident on the system per unit area. The SHGC is a non-dimensional value and revealed by studies that the higher SHGC, the better for heating load in winters but the worse in summers because of the higher cooling load. The SHGC is closely related to building energy load, but the related codes and ratings of fenestration are focused on the U-factor, so that more researches on the SHGC are needed. This is a study of the NFRC 201 for fabricating Solar Calorimeter that can measure the SHGC of the fenestration outdoors.