As I write this month's column we are just coming to the end of the transitional provisions period for Part L 2010.
Any site that would have qualified by submitting an Initial Notice before 1 October 2010 which has not started at least one dwelling by 1 October 2011 will now need to fully comply with Parts L, F and J 2010 and the 25 percent increase in energy efficiency over the 2006 editions.
So we have now had Part L 2010 for just over a year and to be truthful, we are only just starting to see a large number of sites and developments coming through to the new regulations so it is only now that we are starting to get a real feel for the challenges and teething problems that the new requirements bring.
DESIGN UP FRONT
The first challenge is the requirement to effectively complete the design in terms of energy efficiency, and submit a design stage SAP (SAP is the Government’s Standard Assessment Procedure for Energy Rating of Dwellings) before work commences on the building on site, in addition to providing an 'as built' SAP when the building is complete. Now we all know construction and the industry and this type of thing just don’t happen easily. Most of the time, whether it’s a small domestic extension or a multi storey office block, most of the information is ‘to follow’ whilst work on site continues merrily away, so the need to supply a complete thermal design up front on a new house or conversion is a change in thinking for everyone.
Of course the reason for wanting the design sorted so early is the fact that it's really important to ensure that certain details are built in right from the start, as to correct them later in the build process would be extremely difficult and very expensive.
A BRIDGE TOO FAR...
The most contentious of the areas that need to be built in right from the start is thermal bridging. In previous editions of Part L and SAP it was satisfactory to use the Government produced accredited details and input a default value into SAP which would get you a pass. Part L 2010 requires much more work involving individual worked up calculations for each window/wall/roof junction. There is an option to use accredited details specifically designed for Part L 2010 but unfortunately these are not yet available and are unlikely to be completed for some time yet. The fall back position is to use a default value which makes it extremely difficult to get a pass using fabric only solutions.
WHERE’S THE PARTY?
The third challenge is the party wall. Previously thought to be a "neutral" zone in terms of heat loss, it has been discovered that a clear cavity acts as a chimney, with heat from the two adjoining dwellings passing into the cavity and rising up to exit at the top.
Leaving the cavity party wall as it was before, again makes it difficult to get a pass in SAP so it is necessary to provide edge sealing to the cavity or provide edge sealing and fully fill the cavity with insulation. This sounds easy enough, but as with accredited details for thermal bridging, there are no approved details of what is effective edge sealing. Industry is working hard to devise possible solutions and NHBC and the Building Control Alliance is contributing to the process but it is still a slow process.
Now, of course these teething problems will work themselves out as more and more development is built to the new Part L but for the time being if you have any difficulties speak to your SAP Assessor or Building Surveyor at NHBC for further advice.
The transitional provisions for Part L 2010 have now ended and all new developments which didn’t meet the provisions will need to comply fully with the new regulations
Design details for thermal efficiency need to be provided before work commences on site as well as when complete
NHBC Technical Extra 3 provided further details and advice on complying with Part L 2010 – download for free from www.nhbc.co.uk
More details on Part L 2010 can be found in NHBC’s Technical Extra 3 – Part L Special which can be downloaded free from www.nhbc.co.uk