for energy required
for heating or cooling. In the US, the typical standard
is 65ºF (18.3ºC). For each 1ºF decrease or increase from this standard in the average
outside temperature one heating or cooling degree day is recorded. For example, if the average outside temperature for a day was 60ºF, it records as 5 heating degree days (HDD); if it was 70ºF, it records as 5 cooling degree days (CDD).