To reduce the building energy consumption, the major advanced nations are conducting actively many researches on so called a "self-sufficient building(or other words zero energy building)" which can support its required energy by itself. Given this background, KIER(Korea Institute of Energy Research) built full size test-bed of the zero energy solar house in early 2001, and has studied on the self-sufficient heating load up to now. We analyse the sensitivity between the heating load and the solar radiation gain according to the change the effective transmittance of windows. The authors classified 9 cases by solar transmittance of glass. The results demonstrate the solar radiation amount is 0.466 MWh from the eastern zone of Fl.,1(the first floor), 0.332 MWh from Fl.,2(the second floor), 1.194 MWh form the southern zone of F1., and 0.822 MWh from the southern zone of Fl.,2 on the case 1(each cases are classified by window types). On the case 9, the solar radiation amount is 3.127 MWh, 2.662 MWh, 8.799 MWh and 6.078 MWh from the same condition. For the Fl.,1, the amount of Heat Load that is saved per year ranged 10.5 to 48%, and the reduction was anywhere from 0.2 to 17.9% for Fl.,2.