It is recognised that energy efficiency requires integrated design of buildings to minimise the demand for energy in order to obtain the desired environmental performance and to minimise dependence on electro-mechanical systems - for illumination, ventilation or cooling/heating. Integrated design requires a combination of three levels of building design:
- The first requires the configuration of the building plan to control exposure to the external conditions according to the climate.
- The second level requires an informed selection of materials for the building envelop – walls and roof, and the design of windows. These are the passive energy efficiency measures.
- The third level requires the selection and integration of energy efficient cooling and heating equipment to obtain the desired levels of comfort when passive measures do not suffice.