Ashrae Climatic Design Conditions 2025 Guidelines. ©2025 this website describes the activities of the ashrae project committee 169, climatic data for building design standards. I believe ashrae's published design temps have for a long time been the 0.4% & 1% & 2.0% and 97.5% & 99% & 99.6%, temperature bins based on the most recent 25 year.

The american society of heating refrigerating and air conditioning engineers (ashrae) provides multiple sets of outside air (oa) design values in its fundamentals. The ashrae thermal guidelines provide a method for evaluating alternative conditions, balancing the need for further energy saving than is possible in the standard.