Introducing Degree Days to Building Thermal Climatic Zoning in China

Building thermal climatic zoning is a key issue in building energy efficiency. Heating degree days (HDD) and cooling degree days (CDD) are often employed as indexes to represent the heating and cooling energy demand in climatic zoning. However, only using degree days may oversimplify the climatic zoning in regions with complex climatic conditions. In the present study, the application of degree days to current building thermal climatic zoning in China was assessed based on performance simulations. To investigate the key indexes for thermal climatic zoning, the climate characteristics of typical cities were analyzed and the relationships between the climate indexes and heating/cooling demand were obtained. The results reveal that the annual cumulative heating load had a linear correlation with HDD18 only in regions with small differences in altitude. Therefore, HDD is unsuitable for representing the heating demand in regions with large differences in altitude. A comprehensive index (winter climatic severity index) should be employed instead of HDD, or complementary indexes (daily global solar radiation or altitude) could be used to further divide climate zones. In the current official climatic zoning, the base temperature of 26 degrees C for CDD is excessively high. The appropriate base temperature range is 18 degrees C to 22 degrees C. This study provides a reference for selecting indexes to improve thermal climatic zoning in regions with similar climates.

Automated summary

Building thermal climatic zoning is crucial for building energy efficiency. The use of heating degree days (HDD) and cooling degree days (CDD) in climatic zoning may oversimplify regions with complex climates. This study assessed the application of degree days in China's current building thermal climatic zoning and found that alternative or complementary indexes, such as the winter climatic severity index or daily global solar radiation and altitude, should be considered in regions with varying altitudes. Additionally, the base temperature for CDD in the official climatic zoning should be adjusted to a range of 18-22 degrees Celsius. This research provides guidance for improving thermal climatic zoning in regions with similar climates.