A unit used in meteorology and engineering to measure the demand for heating or cooling.
In the United States the agreed critical outside temperature is 65°F (18.3°C). Below this tempeature heating is needed and above it cooling is needed.The number of degree days recorded on a given date is equal to the difference between 65°F and the mean temperature for that date (the average of the highest and lowest temperatures for the day).
- Cooling degree days are recorded if the mean temperature is above 65°F
- Heating degree days are recorded if the mean temperature is below 65°F
The total number of heating and cooling degree days recorded in any period of time is proportional to the demand during that time for energy used in heating and/or cooling buildings.
Subjects: Heating Ventilation and Air Conditioning