Weather Normalization of Building Cooling Energy Consumption Using Specific Enthalpy

Weather normalization is essential when conducting building energy benchmarking or comparing the energy consumption of similar buildings in different climate regions. Degree-days, which is derived from outdoor air temperature, has conventionally been used as an index to represent the weather condition in normalization. However, both air temperature and humidity affect the energy demand of a building cooling system. Existing literature considered the impact of separate weather parameters such as solar radiation and wind speed on weather normalization. This paper aims to investigate if Specific Enthalpy of Humid Air, which is a function of both outdoor air dry-bulb temperature and moisture content, can be used as an integrated indicator of weather condition in place of cooling degree-days to normalize long-term cooling energy consumption more accurately. Cooling Enthalpy Hour, which is calculated at each hour of weather conditions above a reference enthalpy value, is proposed to be the indicator. To test this hypothesis, simulated hourly energy consumption data was normalized using both Cooling Degree Hour and the proposed Cooling Enthalpy Hour as representation of weather variation. Preliminary results showed that the proposed method derived more consistent energy consumption irrespective of weather variation. This demonstrates that Cooling Degree Hour is not highly representative of the varying weather condition that should be normalized from the data.