Degree Days are a function of outside air temperature, compared to a ‘base temperature’, over a period of time. In commercial real estate applications, the base temperature selected should represent an outside air temperature that would result in no (or minimal) heating or cooling required within the subject building.
Heating degree days ‘accumulate’ when outside air temperatures are below the defined base temperature. During these conditions, building heating systems and equipment (and the energy sources for these systems) would generally be operating in order to maintain the desired interior space temperatures for occupant comfort.
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