A Degree Day is a measure used to quantify the demand for energy required to heat or cool a building. It is calculated by comparing the average outdoor temperature to a base temperature (typically 15.5°C in the UK for heating). For example, if the average outdoor temperature on a given day is 10°C, the Degree Days for that day would be 5.5 (15.5°C – 10°C). This metric is essential for estimating energy consumption, sizing heating systems, and assessing building performance.
Degree Days are widely used in the UK house building, residential retrofit, and home renovation sectors to ensure heating systems are appropriately designed and energy-efficient. They are particularly relevant when complying with Part L of the Building Regulations (Conservation of Fuel and Power), which mandates energy efficiency standards. For instance, when retrofitting insulation in a home, Degree Days can help assess the potential reduction in heating demand and energy savings.
Synonym(s): Heating Degree Day (HDD), Cooling Degree Day (CDD)
Practical Example:
A homeowner in Manchester plans to install a new boiler. By analysing historical Degree Day data, they can estimate the annual heating demand and select a boiler with the correct capacity, avoiding oversizing (which wastes energy) or undersizing (which compromises comfort).
Related Terms:
- Base Temperature: The reference temperature used in Degree Day calculations, typically 15.5°C in the UK for heating.
- Heating Degree Day (HDD): A measure of how much and for how long the outdoor temperature is below the base temperature, indicating heating demand.
- Cooling Degree Day (CDD): A measure of how much and for how long the outdoor temperature is above the base temperature, indicating cooling demand.
- Energy Performance Certificate (EPC): A document that rates a building’s energy efficiency, often influenced by heating and cooling demands calculated using Degree Days.
- U-Value: A measure of heat loss through a building element, such as walls or roofs, which directly impacts heating demand and Degree Day calculations.
- Part L (Building Regulations): The section of UK Building Regulations that sets standards for energy efficiency, referencing Degree Days for heating system design.
- Retrofit Insulation: Improvements made to existing buildings to reduce heat loss, often evaluated using Degree Days to estimate energy savings.