How Much Do HVAC Loads Change Due to the Variability of Year-to-Year Weather?

Typical year weather files give a convenient snapshot of the likely weather conditions in a location. However, they provide no information of the year-to-year variability of the weather, which can have a dramatic impact on a building's heating and cooling energy use. This presentation shows a procedure using the variable-base degree day method to determine from the period of record which years would produce the highest heating or cooling loads and calculate the standard deviation in loads from the typical year. These results are building-specific, depending on how sensitive is the building to conduction, convection, or radiation heat flows.