How Does Sefaira Determine the ASHRAE Climate Zone?

In Sefaira’s Real-Time Analysis plugins, when an ASHRAE Baseline is selected, Sefaira automatically selects an appropriate ASHRAE Climate Zone based upon your project’s location.

Sefaira calculates the ASHRAE Climate Zone based upon temperature data from the weather file associated with your project location, using the criteria described in ANSI/ASHRAE/IESNA Standard 90.1-2007 Normative Appendix B – Building Envelope Climate Criteria. These criteria are based upon Heating Degree Days (HDD) and Cooling Degree Days (CDD), and are summarized in the table below.

In some cases the ASHRAE criteria are not explicitly defined, in which case we added additional criteria. For example, CCD10C of 2000 and HDD18C of 2000 can be both 3C and 4A or 4B. In this case, we added additional criteria to HDD for 4A and 4B of 2000 < HDD18C <= 3000.

The ASHRAE Climate Zone is used in combination with the Building Type to establish default envelope properties for your building. (You can look up the properties associated with various baselines here.)

Note that the calculated Climate Zone can differ from the climate zone maps published by ASHRAE. This is because the maps aggregate weather data across a county, province, or region, whereas Sefaira calculates the climate zone for each individual location. It may also be due to differences in the specific weather files used by ASHRAE and Sefaira.

You can change the ASHRAE Climate Zone by clicking on the dropdown in the “Properties” window.


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