Prediction of solar heat gain of double skin facade windows
A linear model involving the solar heat gain coefficient and U value is often used to calculate the solar heat gain of traditional windows; however, it is not known if such linear model is applicable to double skin facades, which is typically featured by ventilated cavity and often with blinds inside. This paper reports on an experimental investigation into the relation between the two coefficients and the energy gain by a double skin facade without blinds. A small-scale solar calorimeter was constructed to measure the energy gain of a double skin facade window about 1.1 m high. Four tests with solar radiation intensity ranging from 205 to 793 W/m2 showed that the energy gain can be represented by such linear model. The solar heat gain coefficient can be determined from the data fitting process with more accuracy than the U value, which, being a minor determinant of the heat flow in the presence of the solar radiation, may require more data for reasonable accuracy. The advantage of this linear model lies in its simplicity, which makes it easy to incorporate into present building energy simulation tools.