Energy efficiency is a way of managing and restraining the growth in energy consumption. Something is more energy efficient if it delivers more services for the same energy input, or the same services for less energy input.
The energy performance of a building shall be determined on the basis of the calculated or actual annual energy that is consumed in order to meet the different needs associated with its typical use and shall reflect the heating energy needs and cooling energy needs (energy needed to avoid overheating) to maintain the envisaged temperature conditions of the building, and domestic hot water needs. (Source: Energy Performance of Buildings Directive of the European Union)
A building is energy efficient when it:
- Produces renewable energy in the premises.
- Fulfils the energy needed by the user for heating, lighting, cooling, etc. according to levels that are specified for the purposes of the calculation.
- Takes care of the “natural” energy gains – passive solar, ventilation cooling, daylight, etc. together with internal gains (occupants, lighting, electrical equipment, etc.).
- Efficiently uses energy, water, and other resources.
- Protects occupant health and improves productivity.
- Reduces waste, pollution and environmental degradation.