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Summary of the Changes to the Conservation of Fuel and Power Building Regulations (2013)

16 March 2015 No Comment

Introduction to changes

The latest amendment to the England AD-L2 and Wales Part L Regulations for the conservation of fuel and power (2013) came into effect on 6 April and 31 July 2014 respectively. This is the third amendment following the introduction of these mandatory regulations in 2002. The revision to Section 6 Scotland is scheduled for 2015.


AD-L2 follows the principle of the 2010 Regulations but with significant changes in the definition of the types of buildings that make up the aggregate mix. As before, the whole building is assessed using the SBEM ‘whole building methodology’ that expresses the energy performance. Since it is the building services that emit CO2 and not the building elements, the total energy building performance takes account of the CO2 emission resulting from the provision of heating, hot water, ventilation, cooling and lighting. It is therefore based on the building’s use in occupation.

In Part L 2010, two notional buildings were defined for top-lit (warehouses) and side-lit (all other) buildings. In Part L 2013 notional buildings reflect the different energy profiles and building services plant likely to be found in the buildings and are defined for:

  • Top-lit (warehouses – further defined by size)
  • Side-lit (heated only)
  • Side-lit ( heated and cooled)

The major change for non-domestic buildings is that they have been divided into seven building types (Table 1) to conform to the national building specifications. A specific Notional Building has been calculated for each within the SBEM model. The main building types have been allocated a target energy/carbon emission saving over 2010 levels that is considered achievable with improvements only to the fabric and services in the notional building. This approach represents an average saving over all building types of 9%.

The target savings are different for each group and have been programmed into SBEM or the equivalent compliance models.

New notional building types for 2013


In order to achieve the 9% target improvement in energy/carbon emissions for 2013, the set values in the Notional Building have been further improved compared to 2010, including:-

  • Lower air permeability rate
  • Improvements to lighting and controls
  • Improved efficiency of services and controls
  • Limitations on the effect of solar gain

However fabric U-values have been retained at 2010 levels

Envelope U-values

The U-values used in the 2013 Notional (non-domestic) Buildings together with the backstop values are the same as the 2010 levels with the exception of window U-values. There is no differentiation between heated only and heated and cooled buildings in the notional building.

Fabric U-values and backstop levels



Air Permeability

In AD-L2: 2013 for non-domestic buildings air permeability is the only part of the fabric performance that has been improved beyond the 2010 levels. The major change is that air permeability levels are defined according to ‘Gross Internal Area’ (GIA) becoming lower as the GIA increases. Following the research shown below and representation from EPIC and MCRMA the levels for smaller top-lit buildings (below 250 m2) have been relaxed to 7m3/m2/h.

The table below illustrates the changes which are shown in m3/(h.m2) at 50Pa according to GIA. There is a backstop level of 10 m3/ (h.m2) at 50Pa. The 10 m3/(h.m2) limit is a mandatory requirement for all new buildings except those below 500m2 for which 15 m3/(h.m2) can be adopted without testing.

In Scotland, air permeability is expressed as a ‘recommended limit’ of 10 m3/(h.m2) – the same value as that used in SBEM for Scotland. Testing became mandatory for warrants made after 1 May 2011.

Air Permeability levels by Gross Internal Area (GIA)


Construction Details

AD-L2: 2013 refers to Accredited Construction Details for non-domestic buildings. At the time of publication of this guide no accredited construction details schemes have been approved by the Secretary of State. Until such time that accredited construction details schemes have been approved, the calculated value of linear transmittance may be used in SBEM without any performance penalty being added where this has been calculated by a suitably experienced and qualified person. All Tata Steel’s Technical Service team are trained and experienced and can be

a full set of details for Tata Systems can be found within the product literature and have been calculated by the same method and should be contacted directly for further information.


Our Technical Department will be happy to supply you with more information or discuss the design requirements for your building in conjunction with the Approved Document Part L or the Scottish Technical Standards. Please contact us on 01244 892130 for support.

For further information on all Tata Steel metal cladding systems visit our website (literature downloads) or for an overview of metal cladding systems you can request a CPD on ‘Steel cladding systems for the non-domestic building envelope’ (CPD request).

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