Free cooling hours for different kinds of buildings

Based on the application conditions and calculation methods of economizers in ASHRAE Standard 90.1, and according to the analysis theory and relevant climatic variables put forward by Pacific Northwest National Laboratory, adopts the temperature and enthalpy value as the classifying criteria, classifies the free cooling hours for different kinds of buildings, and obtains the free cooling hours of 268 cities in China, the results can be used as references for designing.