Climatic design conditions in Chapter 14 of the 2009 ASHRAE Handbook - Fundamentals (HOF) are used for the sizing and design of building energy systems to allow for optimal energy efficiency measures and ensure that the energy systems have enough capacity to meet the climatic loads in a probabilistic sense. Regular updating of the climatic conditions is critical in this respect for many practical reasons and to show due diligence in a world of changing climate.

In response to that need, ASHRAE initiated research project 1613-RP, Update Climatic Design Data in Chapter 14 of the 2013 Handbook of Fundamentals, to update the tables of climatic design conditions in the 2013 HOF and in Standard 169. The purpose was to expand on the 5564 worldwide locations present in the 2009 HOF, use a more recent period of record (1986-2010 vs. 1982-2006) to keep track of changes in the climate, fine-tune the clear-sky solar radiation model that was introduced in the 2009 HOF, and add new elements, such as precipitation, which is required by Standard 169 for the calculation of climate zones. An update to the Weather Data Viewer was also required. Finally, the project was to establish (if possible) temperature trends for all locations in the Handbook.