Glossary

Every term our reports use, without the jargon

40 definitions covering the legislation, the standards and the language an assessor writes in. Each one is linked automatically the first time it appears in a guide on this site.

40 of 40 terms

accreditation scheme

An approved body, such as Elmhurst Energy or ECMK, that qualifies, audits and maintains standards for energy assessors permitted to lodge EPCs.

air permeability

A measure of uncontrolled air leakage through a building's fabric, tested for new dwellings and factored into SAP calculations.

boiler efficiency

The percentage of fuel energy a boiler converts into useful heat, a key input to the SAP and RdSAP calculations.

cavity wall insulation

Insulating material injected into the gap between the inner and outer leaves of a cavity wall to reduce heat loss.

communal heating

A shared heating or hot water system serving multiple dwellings from a central plant, common in blocks of flats and assessed differently under RdSAP.

DEC

A certificate showing the actual, metered energy use of a public building, displayed prominently and renewed annually or every ten years depending on floor area.

domestic energy assessor

An accredited assessor qualified to survey existing dwellings and produce RdSAP-based EPCs.

environmental impact rating

A secondary rating on some EPCs showing the property's estimated carbon dioxide emissions, alongside the main energy efficiency rating.

EPC

A document rating a building's energy efficiency from A (most efficient) to G (least efficient), required when a property is built, sold or let.

EPC band

The letter grade, A to G, shown on an EPC. It is derived from the property's SAP or non-domestic energy score.

EPC Register

The Government database holding every lodged EPC for England and Wales, searchable to check a property's current rating and history.

FENSA

A scheme registering installers competent to self-certify replacement windows and doors as compliant with Building Regulations, without a separate council inspection.

floor insulation

Insulation fitted beneath a suspended timber floor or above a solid floor to reduce heat loss into the ground or an unheated space below.

glazing

The glass units fitted to windows and doors. Double and triple glazing use two or three panes with a sealed gap to reduce heat loss compared with single glazing.

habitable rooms

Rooms used for normal living purposes, such as bedrooms and living rooms, counted during a survey to help characterise a dwelling's layout.

heat pump

A heating system that extracts heat from outside air or the ground and transfers it indoors, generally scoring well in SAP due to high efficiency.

heating controls

Devices such as programmers, room thermostats and zone controls that regulate when and how a heating system operates, scored within SAP and RdSAP.

loft insulation

Insulating material laid across a loft floor or between rafters to reduce heat escaping through the roof, one of the cheapest EPC improvements available.

low energy lighting

Light fittings, such as LEDs, that use significantly less electricity than traditional bulbs for the same light output, improving the lighting score in an EPC.

MCS certificate

Documentation confirming a renewable heating or generation system, such as a heat pump or solar PV array, was installed by an accredited installer to recognised standards.

MEES

The regulations setting a minimum EPC band, currently E, below which most rented properties in England and Wales cannot lawfully be let unless an exemption applies.

occupancy assessment

The standard assumption within SAP and RdSAP about the number of occupants in a dwelling, used to estimate hot water and energy demand rather than actual occupancy.

on-construction assessor

An accredited assessor qualified to produce SAP-based EPCs for newly built dwellings from design plans and site checks.

Part L

The section of the Building Regulations covering the conservation of fuel and power, setting the energy efficiency standards new and altered buildings must meet.

primary energy

A measure, shown on newer EPCs, of the total energy a property consumes including the energy used to generate and deliver fuel to the building.

PRS Exemptions Register

The national register where landlords record a valid exemption from MEES, such as where required improvements are not cost-effective.

RdSAP

A simplified version of SAP used to assess existing dwellings from a site survey, applying standard assumptions where detailed data is unavailable.

recommendations report

The section of an EPC listing suggested improvements, their approximate cost and the effect each would have on the property's rating.

RRN

The unique 20-digit number assigned to each EPC on lodgement, used to look up or retrieve the certificate on the EPC Register.

SAP

The Government's methodology for calculating the energy performance of new dwellings, using detailed design data rather than a site survey.

SAP points

The numerical score, roughly 1 to 100 plus, that underlies the SAP or RdSAP calculation and determines which EPC band a property falls into.

SBEM

The calculation methodology used to produce EPCs for most non-domestic buildings, modelling energy use against a notional comparable building.

SEDBUK

A database and rating system recording the seasonal efficiency of domestic boiler models, used by assessors to identify a boiler's likely performance.

solar PV

Roof-mounted panels that generate electricity from sunlight, reducing a property's estimated energy costs and improving its EPC rating.

solar thermal

Roof-mounted panels that use sunlight to heat water directly, reducing demand on the main heating system for hot water.

solid wall insulation

Insulation fitted to the inside or outside face of a solid wall, which has no cavity to fill, typically the largest single improvement recommended on older properties.

thermal bridging

A localised path through a building's fabric, such as a lintel or junction, that conducts heat faster than the surrounding construction, increasing heat loss.

total floor area

The internal measurement of a property's usable floor space, recorded during an EPC survey and used as an input to the SAP or RdSAP calculation.

TRV

A valve fitted to a radiator that automatically adjusts flow to maintain a set room temperature, contributing to a property's heating controls score.

U-value

A measure of how quickly heat passes through a building element such as a wall, roof or window. Lower U-values indicate better insulation.

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