Appendix A: Key terms and abbreviations

  1. Key terms
    1. Abbreviations

      Key terms

      Table: terms 1The following are key terms used in this document: Air permeability is the physical property used to measure airtightness of the building fabric. It is defined as air leakage rate per hour per square metre of envelope area at the test reference pressure differential of 50 pascals (50 N/m²). The envelope area, or measured part of the building, is the total area of all floors, walls and ceilings bordering the internal volume that is the subject of the pressure test. This includes walls and floors below external ground level. Overall internal dimensions are used to calculate this envelope area and no subtractions are made for the area of the junctions of internal walls, floors and ceilings with exterior walls, floors and ceilings. The limiting air permeability is the worst allowable air permeability. The design air permeability is the target value set at the design stage, and must always be no worse than the limiting value. The assessed air permeability is the value used in establishing the DER and the DFEE rate, and is based on a specific measurement of the dwelling concerned or on measurements of other dwellings of the same dwelling type. NOTE: The envelope area of a terraced house includes the party wall(s). The envelope area of a flat in a multiple-storey building includes the floors, walls and ceilings which are shared with adjacent flats. BCB means building control body - a local authority or an approved inspector. Commissioning is the advancement of a fixed building service after all or part of the system has been installed, replaced or altered. The system is taken from a state of static completion to working order. Testing and adjusting, as necessary, ensure that the whole system uses no more fuel and power than is reasonable in the circumstances, without compromising the need to comply with health and safety requirements. For each system, commissioning includes the following: setting-to-work; regulation (that is, testing and adjusting repetitively) to achieve the specified performance; calibration, setting up and testing of the associated automatic control systems; and recording of the system settings and the performance test results that have been accepted as satisfactory. Controlled service or fitting means a service or fitting in relation to which Part G (sanitation, hot water safety and water efficiency), H (drainage and waste disposal), J (combustion appliances and fuel storage systems), L (conservation of fuel and power) or P (electrical safety) of Schedule 1 to the Building Regulations imposes a requirement. DER is the Dwelling CO2 Emission Rate expressed as kgCO 2 /(m² .year). DFEE rate is the dwelling fabric energy efficiency rate expressed as kWh/(m².year). Dwelling means a self-contained unit designed to accommodate a single household. NOTE: Buildings exclusively containing rooms for residential purposes, such as nursing homes, student accommodation and similar, are not dwellings, and in such cases, Approved Document L2A applies. Dwelling type is the particular group allocated to each dwelling on a development to provide the basis for assessing the pressure testing regime. The allocation of each dwelling to a dwelling type should be the responsibility of the person carrying out the pressure testing. To be classed as of the same type, dwellings should:

      i. be of the same generic form (i.e. detached, semi-detached, end terrace, mid-terrace, ground- floor flat (inclusing ground-floor maisonette), mid-floor flat, top-floor flat (including top-floor maisonette);

      ii. include the same number of storeys;

      iii. have the same design air permeability;

      iv. have similar adjacency to unheated spaces such as stairwells, integral garages etc.

      v. have the same principal construction details;

      vi. have a similar (i.e. ± 1) number of significant penetrations, i.e. for windows, doors, flues/ chimneys, supply/exhaust terminals, waste water pipes;

      vii. have envelope areas that do not differ by more than 10 per cent (see air permeability for a definition of envelope area).

      Energy efficiency requirements means the requirements of regulations 23, 25A, 25B, 26, 26A, 28 and 40 of, and Part L of Schedule 1 to, the Building Regulations. Energy performance certificate means a certificate which complies with regulation 7A of the Energy Performance of Buildings (England and Wales) Regulations 2012. Fixed building services means any part of, or any controls associated with—

      (a) fixed internal or external lighting systems (but not including emergency escape lighting or specialist process lighting);

      (b) fixed systems for heating, hot water, air conditioning or mechanical ventilation; or

      (c) any combination of systems of the kinds referred to in paragraph (a) or (b).

      Room for residential purposes means a room, or a suite of rooms, which is not a dwelling-house or a flat and which is used by one or more persons to live and sleep and includes a room in a hostel, an hotel, a boarding house, a hall of residence or a residential home, but does not include a room in a hospital, or other similar establishment, used for patient accommodation. TER is the Target CO2 Emission Rate expressed as kgCO2 /(m².year). TFEE is the Target Fabric Energy Efficiency rate expressed as kWh/(m².year).


      CO2: carbon dioxide BRUKL: Building Regulations UK Part L UKAS: The United Kingdom Accreditation Service SEDBUK: Seasonal Efficiency of Domestic Boilers in the UK TFA: total floor area TMP: thermal mass parameter

      • Table 1 Fuel factor Table 1 Fuel factor
      • Table 1 Fuel factor Table 1 Fuel factor
      • Table 2 Limiting fabric parameters Table 2 Limiting fabric parameters
      • Table 3 U-values for party walls Table 3 U-values for party walls
      • Table 4 Summary of concurrent notional Table 4 Summary of concurrent notional dwelling specification
      • Table 4 Summary of concurrent notional dwelling specification (continued) Table 4 Summary of concurrent notional dwelling specification (continued)
      • Parameter Parameter