Energy performance is the energy needed for a building’s heating, cooling, domestic hot water, ventilation and, in some cases, lighting. It expresses efficiency and is summarised in the Energy Performance Certificate (APE).
The main framework is Legislative Decree 192 of 19 August 2005, implementing European building-energy directives and subsequently amended. Article 6 governs the APE, certifying the property’s rating and providing information on its energy characteristics.
Performance depends on both the building envelope and its systems. Thermal insulation is a major factor: walls, roofs, floors and ceilings must limit heat exchange with the outside. Good insulation reduces winter heat loss and summer overheating, lowering energy demand for a comfortable indoor temperature.
Windows and frames also matter. Low-emissivity glazing, double or triple glazing and efficient frames reduce heat loss and improve comfort, whereas old or poorly insulated units can lose considerable energy.
Heating, cooling and hot-water systems are decisive. High-efficiency boilers, heat pumps, automatic temperature controls and modern installations reduce consumption compared with obsolete equipment.
Renewables, including photovoltaic and solar-thermal installations, generate clean energy on site, reducing reliance on conventional sources and improving the rating.
Orientation, exposure and geographical location also influence results. A well-oriented home uses natural sunlight more effectively, reducing heating and lighting demand. Climate zone is included in the assessment.
Construction materials, building age, thermal bridges and design quality are further factors. New buildings built to higher standards generally consume less than older properties unless the latter have been upgraded.
Ratings range from A4, the most efficient, to G, the least efficient. Classification is based on the global non-renewable energy performance index: the non-renewable primary energy needed to meet the building’s demands.
Improvements include insulating the envelope, replacing windows and heating or cooling systems, installing photovoltaic panels and introducing intelligent consumption management.
Energy performance also has economic importance: a more efficient home generally costs less to run and may achieve a higher market value. The APE must accompany sale and tenancy contracts as required by the applicable rules.