A cornerstone of design performance and energy modeling is access to relevant climate data. Climate data is the basis for the climatological conditions a structure will be subjected to during a computational analysis. Intuitively, we understand the broadly generalized differences between locations like Phoenix versus Minneapolis. However, a computer program needs more than intuition, it needs data.
Climate data defined
In the most simple terms, the climate data files accessed by energy modeling programs contain annual, monthly, daily, and even hourly climate data averaged out over a defined period of time – typically 30 years. Such collections of three-decade averages of climatological variables are known as Climate Normals. Climate Normals are produced once every ten years – with the latest available data ranging from 1981-2010 (released in July 2011).
Managed by the National Oceanic and Atmospheric Administration’s (NOAA) National Climatic Data Center, Climate Normals data sets will include a wide range of information such as temperature, precipitation, and heating/cooling degree days.
One of the best online resources for climate data files is provided by the U.S. Department of Energy:
This website contains data from over 2,100 locations worldwide – including 1,042 locations in the U.S. The weather data is arranged by the World Meteorological Organization.
Why 30 years?
A three-decade average is important because the climate can vary a great deal from year-to-year. Basing an energy model on the past one or two years may produce unreliable results. Rarely does a short-range sample align with long-term averages.