Last edited 19 Oct 2020

Target fabric energy efficiency rate

Dwelling Fabric Energy Efficiency rates (DFEE) and Target Fabric Energy Efficiency rates (TFEE) were introduced by the 2013 edition of approved document L1A of the building regulations, 'Conservation of fuel and power in new dwellings', which came into force on 6 April 2014. The energy performance requirements of the 2013 edition have been strengthened to deliver a 6% carbon dioxide saving across the new homes build mix relative to the 2010 edition.

Dwelling Fabric Energy Efficiency rates and Target Fabric Energy Efficiency rates sit alongside the requirements for Target CO2 Emission Rates (TER) and Dwelling CO2 Emission Rates which were already part of the 2010 edition of the approved document.

The Target Fabric Energy Efficiency rate is the minimum energy performance requirement for a new dwelling approved by the Secretary of State in accordance with regulation 25 of the building regulations. It is expresses as the amount of energy demand in units of kilowatt-hours per square metre of floor area per year (kWh/(m^2.year).

The TFEE is derived from a notional dwelling of the same size and shape as the actual dwelling being constructed. A summary of the Part L 2013 notional dwelling is published in Table 4 of approved document L1A and the full detail is set out in the Standard Assessment Procedure (SAP 2012) Appendix R. However, following responses to the consultation on the 2013 changes, a further 15% is permitted to allow some design flexibility.

The Dwelling Fabric Energy Efficiency rate is the actual energy performance of the new dwelling.

In accordance with regulation 26A of the building regulations, the calculated Dwelling Fabric Energy Efficiency rate must not be greater than the Target Fabric Energy Efficiency rate.

If the actual dwelling is constructed entirely to the notional dwelling specifications it will meet the fabric energy efficiency targets, however, the notional dwelling is not prescriptive and developers are free to vary the specification, provided that TFEE rate is achieved or bettered.

Before work starts, the builder must calculate the DFEE rate of the dwelling as designed, to demonstrate it is not greater than the TFEE rate. The builder must give this design-based calculation to the Building Control Body (BCB) along with a list of specifications used.

When work is complete, the builder must notify the BCB of the DFEE rate and TFEE rate, and whether the building was constructed in accordance with the list of specifications submitted to the BCB before work started. A list of any changes to the design-stage list of specifications must be given to the BCB.

For a building that contains more than one dwelling (such as a terrace of houses or an apartment block), average rates can be used. An average cannot be calculated across separate multiple buildings on a site.

To guard against poor performance of individual elements, limiting fabric values are retained in Table 2 of approved document L1A and limiting building services efficiencies are set out in the Domestic Building Services Compliance Guide.

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