The heat gain-based generation method of coincident weather data for walls with a large thermal lag

The coincident weather data (CWD) means the combination of weather data that affect a moment of indoor heat gains at the same time. It includes the coincidence of dry-bulb temperature, wet-bulb temperature and solar irradiation. The selection of design solar irradiation in the current ASHRAE and CIBSE design handbooks is independent on design dry-bulb and wet-bulb temperature. And the generation methods of CWD in those are based on the original weather data itself. Furthermore, the generation methods in some related literatures are either ignoring the thermal delay and decay of building envelope or not appropriate for engineering using. Hence, a new method based on the hourly heat gain formula, three weather parameters, building heat characteristics and risk factor was developed for the generation of coincident solar irradiance, dry-bulb and wet-bulb temperature. The method was applied to historic weather records of 25 years in Hong Kong and data of 302 kinds of walls to generate coincident design weather data. The result shows that the design dry and wet bulb temperature can be lowered and the solar radiation values are more regular, compared to traditional weather data. In a category of walls, the deviation between the representative parameter and CWD is less than 5%. It’s means that using the new CWD can reduce the building energy consumption, and engineering heat gain calculations can be more precise and concise.