Building Regulations Part L 2013

Date added: 24 February 2012

The Department for Communities and Local Government Consultation on Proposed Changes

This briefing note is designed to provide an outline of the consultation and the governments thinking of how domestic property will be assessed in the future and how to get closer to the 2016 target of ‘zero carbon’.

The government are still targeting all new dwellings to be ‘zero carbon’ by 2016. In order to achieve this, the building regulations between now and this date need to improve the building standards quickly and significantly.

The latest document to be published by The Department of Communities and Local Government is a consultation for the 2013 changes to Part L of the building Regulations.

“2012 consultation on changes to the Building Regulations in England. Section two Part L (Conservation of fuel and power)”

The full document can be found at the following web site:

Timetable for introduction of the changes

Government’s preferred option on timings are:

Summer 2012

Regulations on consequential improvements for domestic extensions laid in Parliament

October 2012

Consequential improvements for domestic extensions come into force

April 2013

Regulations on new build standards, performance standards for works to existing buildings and other consequential improvements laid in Parliament

October 2013

New build standards and performance standards for works to existing buildings come into force

April 2014

Other consequential improvements (domestic boiler and window replacements, and specified other non-domestic works) come into force

As can be expected new lower carbon emission targets are eluded to but not quantified as is the method by which the carbon target is calculated. At present a notional dwelling is created against which the proposed dwelling is measured. One option is to retain this system but the alternative is to set an absolute limit of carbon to be emitted per m2.

By 2016 it is highly likely there will also be a fabric energy efficiency standard as well as a carbon standard to Part L.

Fabric Energy Efficiency Standard

As standards are raised, there is a benefit to recognising the differing abilities of building types to cut energy demand and carbon emissions, apartments and mid-terrace houses have the natural advantage of lower external floor/wall/roof area per dwelling (and thus lower heat loss) than semi-detached and detached houses.

All the options proposed for the 2013 changes have some differentiation between building types.

Assuming that both the fabric energy efficiency and CO2 emission performance targets will be set on an absolute basis in 2016, 2013 will be used as a stepping stone.

The options are:

1. to have a building fabric standard with some services flexibility ‘FEEs plus services’ or
2. absolute minimum standards for building fabric and services (CO2 emissions) at a halfway point to the 2016 expected ‘zero carbon’ standard.

The table below illustrates these options.


The Government’s preference is for a hybrid approach, to align with their preferred ‘FEES plus efficient services’ option. The theory being that some flexibility is retained but still aiding the move towards zero carbon and more efficient building form by introducing an energy target that all buildings must meet.

CO2 emission factors

The Department of Energy & Climate Change are consulting on updated CO2 emission factors alongside their SAP Consultation*. Once finalised and published, Part L compliance calculations will be based upon these updated CO2 factors.


The SAP consultation does consider changing the way carbon emission factors are calculated but the suggestion is that there wll not be significant change and so the difference between the carbon intensity of mains gas and other fuels is unlikely to alter significantly for the purposes of Part L 2013.

Existing Buildings

CLG see the potential to raise the standards for controlled works in existing buildings, where this can be shown to be cost-effective.

They are proposing to extend the requirements for ‘consequential improvements'

This is the term used to describe the use of the Building Regulations to trigger a requirement for extra energy efficiency works in a building where other controlled work is already taking place.

Replacement domestic windows

Currently Approved Document L1B suggests that replacement windows should be the equivalent of a Window Energy Rating Band C or better (broadly equivalent to a whole window unit U value of 1.6 W/m2.K).

The option of raising this to Band B or equivalent (U value of around 1.4) is proposed.


A Fabric Energy Efficiency Standard is proposed but at a lower level than that for new build. (the level is to be confirmed)

Extensions or increases in habitable space

The proposal is to apply the requirements for consequential improvements to all existing domestic buildings which undergo works to add an extension, and also apply it to increases in habitable space (i.e. loft and integral garage conversions). This is for any sized property not just those over 1000m2.

Replacement of controlled services or fittings

For homes CLG propose to limit this to the replacement of a boiler or a percentage of the home’s windows. (percentage to be confirmed)

Determining ‘consequential improvements’

The current statutory guidance in Approved Document L2B sets out that not less than 10% of the cost of the principal works should be spent on other energy efficiency improvements, where this is cost-effective. The guidance recommends that measures should be assessed on the basis of a simple 15 year payback. It is proposed to keep this 10% measure as a guide to the value of works to meet the requirement.

It should be noted that the governments preferred option is to phase in the consequential improvement requirements from October 2012. This aligns with the launch of The Green Deal which can help with the costs of improving a dwellings’ energy efficiency.

At this time all of the above are proposals in a consultation to which responses are invited by 27th March for some items and 27th April for others.

MLM are available to discuss the implications of the proposals and are happy to guide clients to the most effective way of dealing with them.

Please contact our SAP assessor Iain Farquharson on 01473 231100 or

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