Old Homes, New Regs: An overview of the 2010 changes to Approved Document L1B

Dyfrig Hughes

The changes to SAP and Part L are fast approaching. National Energy Services has already produced software to preview the changes, workshops to discuss how they will affect you, and we have also launched a package of online CPD for On Construction DEAs and any other interested parties to dig deeper into the subject. In this guest blog post, Nick Jones of Inbuilt looks at the forthcoming changes to Part L1B of the Building Regulations and the implications for existing dwellings.

As always, in the run-up to a revision of Part L of the Building Regulations there is a great deal of attention focussed on what it means for new build housing, with the inevitable talk of appropriate technologies, costs and diminishing returns. The implications for existing dwellings tend to be consigned to the back pages, if covered at all.

In 2002 we saw an important shift with the introduction of minimum standards for replacement windows and boilers, and 2006 saw the introduction of the concept of ‘thermal Part L1B will introduce insulation  requirements for swimming pool  basinselements’ and threshold U-values. In the case of ‘material change of use’ a wall, roof, or floor could need upgrading even it is not being modified as part of the change. All of these changes were designed to tap into ‘trigger points’: stages in the building’s life where work is being carried out and where improvements are reasonable and enforceable. It is of course the second of these that is so difficult.

This time around there are a few headline changes, some adjustment to detailed requirements, and better guidance on application. There do not seem to be any industry-shaking modifications.

The change that has had the most coverage is the introduction of insulation requirements for swimming pool basins which must now have a U-value no worse than 0.25W/m2K. Whilst this is important, it does not include outside swimming pools, as they are not buildings, and so it is hardly a move that will propel us to the 2050 target of 80% carbon reductions

Part L1B had suggested that all  conservatories be brought into Part L.

Conservatories in Part L

Another headline in the consultation paper was the suggestion that all conservatories should be brought into Part L. The previous exemption for conservatories and porches remains but only for a stated list of situations. Unfortunately this covers (in the hands of a skilful installer) most conservatories.

The only significant difference is that previously they had to have ‘independent temperature and on/off controls for any heating system’ whereas now the exemption only applies ‘where the heating system of the dwelling is not extended into the conservatory or porch’.

There has been some minor tightening of U-values, particularly for new ‘thermal elements’:

Insulation values for new thermal elements in ADL1B, 206 and 2010

Table 1 – Insulation values for new thermal elements in ADL1B 2006 and 2010

There is no longer any mention of limiting U-values since these are mainly concerned with condensation risk and are therefore covered by Approved Document C.

Windows is the one area where there has been an appreciable step up in the requirements for replacement windows to WER Band C or better (or a U-value of 1.6 W/m2K). The consultation document did not give the option of a U-value alternative to window energy ratings (WERs) for windows but this has now changed. A change from 2006 is that the document refers to WERs generally rather than the proprietary British Fenestration Rating Council (BFRC) so opening the way for rival schemes.

U-value requirements have tightened in the new Part L.

Existing thermal elements

For existing ‘thermal elements’, including those elements that were previously not thermal elements, there is a slight tightening of the requirements. This includes garden walls that were previously free-standing but now become part of an extension, and gable walls incorporated in a loft conversion. Walls that had a U-value of 0.7 W/m2K or worse and which have insulation applied internally or externally need to achieve a U-value of 0.30 W/m2K instead of the previous 0.35 W/m2K. Similarly, some roofs also have to achieve better U-values.

Existing thermal elements that are replaced now have to meet the same standard as for new elements, whereas previously there was a slight relaxation.

In all cases the option remains of using SAPs to demonstrate that the building is better than if the elemental values had been applied.

While the 2006 document was fairly clear about the standards that needed to be achieved, it was less clear on some of the trigger points when it came to refurbishing individual elements. When more than 25% of an element was being refurbished then the requirement was applicable but 25% of what? In the case of walls, did that apply when 25% of all external walls were being refurbished, 25% of any facade, or in the case of internal insulation 25% of the external walls of a particular room? Now we have much more specific information and examples.  The trigger points are 50% of the surface of the individual element and 25% of the building envelope (this aligns with the EPBD definitions). The examples in the AD make it clear that if 50% of the inner surface of an external wall in one room is renovated then the regulations apply. The previous provisos about reasonableness and applying lesser provisions where the work will reduce floor space by 5% still apply.

For building services much of the detail has been pushed into the Domestic Building Services Compliance Guide (formerly the Domestic Heating Compliance Guide) including the lighting requirements which no longer require use of dedicated fittings. The reasoning is that tungsten lamps are being phased out, however this ignores the fact that people can still replace standard low energy lamps with halogens as soon as the work is done - but then the same was true of dedicated fittings to some extent. The loophole on insulating primary pipework still remains so that many primary circuits do not need to be insulated. This also applies to newbuild.

The extent to which building control need notification is also clarified. With the exception of emergency works and where competent persons are used, pretty well everything is notifiable. Of course, this does not necessarily mean that this will happen in practice. The list of competent persons and range of work covered by schemes is growing but does not cover every trade and it would take a massive information campaign to inform every jobbing builder and plasterer of their obligations.

Inevitably there has been much discussion about taking care of historic buildings and the previous exemption list of listed buildings, those in conservation zones, and ancient monuments has been extended. Three further categories are now included which covers buildings that are of architectural and historic interest that are on stated lists, or in particular areas: buildings included as material considerations in local area development plans, or located in national parks, for example.

There are a number of layout changes to the document that do make the document easier to use and understand. However there are several new references to other documents and regulations, all of which raise the concern that there may be implications that are not clear in the initial reading.

Despite the overstated headlines about swimming pools and conservatories there are no major shakeups but the document is to be welcomed because of its simplicity and ease of explanation to others. The impact on our stock and the day to day lives of our local building trade is yet to be seen.

This is a guest post written by Nick Jones, Associate Director at Inbuilt - a leading sustainable buildings consultancy. Nick has been involved in house building and energy efficiency for over 20 years. See more about Inbuilt at www.inbuilt.co.uk.

Find out more about the changes

You can learn much more about the changes to Part L by purchasing our package of online CPD modules on the changes to Part L and SAP. It's only £250+VAT, with a £50 discount if you are a NHER/SAVA member.


The views expressed in this blog article are the personal views of the author and do not necessarily reflect the views or policies of National Energy Services.  When submitting a comment, please be aware of the guidelines provided in our website terms and conditions.


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