Energy Efficiency.

Energy efficiency represents how much energy a home uses. A home may be regarded as ‘energy efficient’ or ‘energy inefficient’. An energy efficient home uses little energy.

Various metrics can be used to quantify energy efficiency. The industry standard is a holistic metric which defines a home’s energy efficiency in terms of the regulated component of its delivered energy per square metre of floor area per year. This should be calculated using the SAP methodology, and as a result an energy efficient home can be defined as one that exceeds a certain SAP rating or Energy Performance Certificate (EPC) band.

This definition of energy efficiency takes into account the home’s heating and cooling, appliance efficiencies, ventilation, domestic hot water system, fixed lighting and any renewable energy generation connected to the home, as well as its fabric (insulation, airtightness and thermal bridges). Sometimes the term ‘energy efficiency’ is used to mean just the fabric aspects of the home, ignoring the other features which increase or lower its energy consumption.

(Based on a definition taken from “Carbon Jargon”, an NHBC Foundation report, researched and written by Neil Cutland of Sava).