Building Regulations - England

Supporting documents are available from the government that provide detailed information on each section of the Building Regulations and Standards. EcoTherm has compiled a summary of the insulation related elements of these documents and provided U-values that will help achieve compliance.

The figures and information quoted are for guidance only.  Official Building Regulation / Standard documentation should always be consulted and an approved U-value calculation completed by EcoTherm Technical Services for each project.

New Dwellings (Domestic Buildings) - Approved Document L1A/ADL1A
Approved Document L1A looks at the entire building’s performance and CO2 emissions, rather than isolating one particular element. All dwellings (domestic buildings) must be designed and built so their individual Dwelling CO2 Emissions Rate (DER) is no worse than the Target CO2 Emissions Rate (TER). The TER is based upon the performance of a defined Notional Dwelling.

A new requirement to also reach a Target Fabric Energy Efficiency (TFEE) brings the need to specify improved insulation standards and a focus on thermal bridging and air tightness, again based on a Notional Dwelling. Introducing a target for the Dwelling Fabric Energy Efficiency (DFEE) ensures that a ‘fabric first’ approach is taken throughout the building, which ultimately makes it easier to reach the TER.

Both the Dwelling Emission Rate (DER) and Dwelling Fabric Energy Efficiency (DFEE) are calculated using a calculation methodology called SAP (Standard Assessment Procedure) 2012. If the dwelling is built precisely to match the Notional Dwelling criteria, it should meet the Target Emission Rate (TER) and Target Fabric Energy Efficiency (TFEE). Note that other factors need to be taken into consideration including continuous building fabric insulation, air permeability, thermal bridging, information submission (design and build values) and limiting the effects of heat gains in summer.

The area-weighted average U-values, taken from the Notional Dwelling specification (used to set the TER and TFEE targets), are shown in table 1 below.

The actual specification required for a compliant building and necessary building fabric U-value targets may vary depending on the actual overall proposed specification and the outcome of the energy assessment.

table 1
  Roofs Walls Floors
Notional Dwelling area weighted average U-value 0.13 0.18 0.13

Existing Dwellings (Domestic Buildings) - Approved Document L1B/ADL1B
Existing dwellings differ from new dwellings, in that they do not have to achieve a whole building Target CO2 Emissions Rate (TER, see New Dwellings above). However, existing dwellings do have to meet certain target U-values for building elements (walls, floors and roofs).

The target U-values for existing dwellings or new elements within them are shown in table 2 below.

table 2
  Flat roofs Pitched roofs Walls Floors
For replacement or refurbished roofs New elements (extension/ conversion) For replaced or refurbished roofs New elements (extension/ conversion) Existing walls (refurb) New walls (extensions) New floors (refurb) Existing floors (extension)
Ceiling level Rafter level Ceiling level Rafter level
Required area weighted average U-value 0.18 0.13 0.16 0.18 0.16 0.18 0.30 0.28 0.25 0.22

New Buildings other than Dwellings - Approved Document L2A/ADL2A
Approved Document L2A adopts the same approach to Approved Document L1A, taking the entire building’s performance and CO2 emissions into consideration. All new buildings other than dwellings must be designed and built with their Building CO2 Emissions Rate (BER) being no worse than the Target CO2 Emissions Rate (TER). The TER is set from a Notional Building of same size and shape to the actual building. There are three defined Notional Buildings; heated and cooled buildings (that are side lit or unlit), and toplit buildings. The specification for each building type is summarised in Section 5 of ADL2A. CO2 Emissions Rates for buildings other than dwellings are calculated using the Simplified Building Energy Model (SBEM).

Special considerations are made for low energy demand buildings, modular/portable buildings, temporary buildings, industrial sites, workshops, and non-residential agricultural buildings. ADL2A should be consulted for further details. If the building is built to match the Notional Building specification, its BER should meet the TER. Note that other factors need to be taken into consideration including continuous building fabric insulation, air permeability, thermal bridging, performance testing and limiting the effects of heat gains in summer.

The area weighted average U-values, used in the Notional Building specifications for setting the TER, are shown in table 3 below.  The actual specification required for a compliant building and necessary building fabric U-value targets may vary depending on the actual overall proposed specification and the outcome of the energy assessment.

Although ADL2A is for new buildings other than dwellings, there are some exceptions if a dwelling is featured within the new building. For more details on these exceptions ADL2A should be referred to.

table 3
  Roofs (pitched & flat) Walls Floors
Notional Dwelling area weighted average U-value 0.18 0.126 0.22

Existing Buildings other than Dwellings - Approved Document L2B/ADL2B
Existing buildings do not require a Target CO2 Emissions Rate, however they do require a target U-value to meet for building elements (walls, floors and roofs).

The target U-value for flat roofs on existing buildings other than dwellings are shown in table 4 below.

table 4
  Flat roofs Pitched roofs Walls Floors
For replacement or refurbished roofs For replaced or refurbished roofs New elements (extension/ conversion) Existing walls (refurb) New walls (extensions) New floors (refurb) Existing floors (extension)
Ceiling level Rafter level Ceiling level Rafter level
Required area weighted average U-value 0.18 0.16 0.18 0.16 0.18 0.30 0.28 0.25 0.22

If you need any assistance or clarification regarding Building Regulations for your upcoming project, get in touch with our Technical team

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