Fourier MultiLogPRO User Manual page 59

required to keep that structure at 65°F when the temperature remains 24°F
below that 65° threshold for 1 hour.
Likewise, one cooling degree–day is the amount of cooling required to keep a
structure at 65°F when the outside temperature remains one degree above the
65°F threshold for 24 hours. One cooling degree–day is also the amount of
cooling required to keep that structure at 65°F when the temperature remains
24°F above that 65° threshold for 1 hour.
Both heating and cooling degree-days can accumulate in the same day. Also,
note that there are no negative degree-days. If the temperature remains below
the threshold, there is no degree-day accumulation.
Heating and cooling degree-days are usually calculated by either the High/Low
method or the Integration method.
WeatherLab uses the more accurate integration method.
In the integration method, the software calculates degree–days using the
average temperature for a saving interval and the saving interval time. For
example, if the average temperature during a 15 minute interval was 24° below
the base threshold, the software would calculate 0.25 heating degree-days
during that interval (24  15 minutes in interval/1440 minutes per day). The
number of degree-days during each interval are added together to arrive at a
degree-day total.
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