PARAMETERIZATION STUDY OF THE OVERALL THERMAL-TRANSFER VALUE EQUATIONFOR BUILDINGS

Modern buildings in Hong Kong are characterized by high window-to-wall ratios. This leads to large energy consumption due to the solar radia tive heat gain. The problem is now of great concern to the industry no t just because of the energy usage, but also due to the environmental problem that arises from overusage of energy. The government is consid ering implementing some regulations for controlling the cooling load i n centrally air-conditioned buildings, The concept of overall thermal- transfer value (OTTV) is proposed to be used as a guideline for design ing the building envelopes. However, those equations for calculating t he OTTV recommended by the draft design guide are rather unclear. Many parameters that influence the OTTV equation have not been studied tho roughly yet. This paper aims at carrying our a parameterization study on the OTTV equation. The window-to-wall ratio, shading coefficient, w all absorptance and wall heat capacity are found to be important param eters. Modification of the equivalent temperature that appears in the OTTV equation is recommended Finally, the effect of overhang on the so lar load value is also investigated.