Assessing the energy performance of a building

Conducting energy assessments

Only an accredited domestic energy assessor may carry out an energy assessment and produce an EPC for a building. For newly constructed buildings the EPC can only be produced by an accredited on construction domestic energy assessor.

Energy assessors can be self-employed, employees of service organisations, such as surveyors or energy companies, or employees of the landlord or owner. Energy assessors must be a member of a government approved accreditation scheme.

Energy assessors must act in an independent manner and must declare any conflict of interest when undertaking an assessment. Conflicts of interest include, but are not limited to, a situation where the energy assessor has employment links with an organisation or is related to the person who commissioned the EPC.

Energy assessors must identify conflicts of interest and raise concerns with their accreditation scheme if they feel they have been asked to implement practices which run contrary to this.

Energy assessor accreditation

Accreditation schemes are responsible for managing energy assessors and for ensuring their assessors are competent and possess the appropriate skills to conduct an energy assessment for the building. Energy assessors will need to be qualified for the type of building being assessed. To become a member of an accreditation scheme the energy assessor must:

• demonstrate their competence, by either having a recognised qualification from an awarding body or approved prior experience and learning equivalent to national occupational standard requirements
• maintain appropriate professional indemnity cover
• update their skills and knowledge regularly
• participate in the accreditation scheme quality assurance procedures
• abide by the accredited scheme advice and guidance

How the energy performance of a building is calculated

The energy rating of a building is a complex calculation which is based on a combination of factors:

• the type of building (i.e. flat, house or bungalow) and whether it is detached or not
• the age of the building
• the number of habitable rooms (excluding kitchens, bathroom hallways, stairs and landings)
• extensions and their construction and rooms in the roof
• the dimensions of the building and the number of floors
• the amount and type of glazing (i.e. single or double glazing)
• the material used to build the property (e.g. brick, stone, timber frame, etc.)
• wall insulation
• roof construction (e.g. flat, pitched) and insulation
• the number of chimneys and open flues
• the heating systems and the type of fuel used

The energy rating is adjusted for the floor area of a building so it is independent of size for a given type of building. The rating is calculated on the basis of standard occupancy to ensure that the results are consistent for similar building types and relate to the physical fabric of the building rather than the energy usage patterns of the individual occupant, which can vary appreciably between households.

The rating is independent of the number of people living in your household, how many domestic appliances you own (such as washing machines and refrigerators) and how efficient they are and how you choose to heat your home (i.e. individual temperature settings and how long it is heated during the day or night). This allows prospective buyers or tenants to compare the energy rating of buildings on a like for like basis.