Your energy consumption can be directly affected by factors such as whether your building is occupied, the occupant’s behaviour, the temperature outside or production levels. Unless these factors are taken into consideration, your evaluation of energy performance could be misleading.
Possibly the most prevalent driving factor is temperature. When analysing energy consumption that is affected by the outside temperature, we need a measure of the time when (and how much) heating or cooling was required. Degree days can provide us with this information.
What is a Degree Day?
Degree days are a measure of the duration and magnitude of the difference between the external temperature and a base temperature. The base temperature is the external temperature at which additional heating or cooling is required to maintain a comfortable environment in your building.
The greater the difference between internal and external temperature, the quicker heat will be lost from your building. The longer the colder period lasts, the more heat will be lost. The colder your building gets, the more energy is required to keep it warm. A heating degree day is a measure of both the difference and duration of the cold outside.
For cooling, the opposite is the case. The longer and higher the temperature is above the cooling base level, the more cooling degree days and the greater the energy required by the cooling system.
Base Temperatures
Base temperatures will vary depending on the building. Factors such as the required internal temperature, building insulation and other heat gains will all affect the level of the Base Temperature.
Use the Base Temperature Analysis Static reports to calculate a recommended value.
Calculating Degree Days
To calculate the heating degree days for a day, we sum the temperature difference for each 30-minute interval when the external temperature is below your heating base temperature. When the external temperature is equal to, or above the base temperature, the differences are treated as zero (there is no heating requirement).
As there are 48 half hour periods in a day, this value is divided by 48 to convert our summed degree half-hours into the number of degree days for that day.
Set your location and change your default Base Temperature (if required) and site-specific Degree Days are calculated for you.