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Demystifying Part L 2010

24 January 2011

With changes to Part L of the Building Regulations in England and Wales in 2010 on the horizon, now is the time for the glazing industry to get to grips with the forthcoming Building Regulations and inform architects and specifiers about how low- energy glazing and windows can affect compliance.

The Government’s CLG (Department for Communities and Local Government) has a well-publicised timeline for improving the requirements of Part L in stages up to 2016. In 2006, immediately after the last change to Part L, the following targets for energy and carbon improvement were set out for dwellings: 2010 – by 25 per cent, 2013 – by 44 per cent, 2016 – by 100 per cent. For non-dwellings, CLG’s targets are still to be confirmed, but it is likely they will adopt the same improvement levels as dwellings in 2010 and 2013, delaying zero-carbon standards until 2019.

This does not mean that every component of a building will have to improve. The requirements for new buildings are, and will continue to be, based on the total energy performance of the whole building, meaning higher performance windows will be required. In the case of replacement windows, CLG has indicated that, because the requirements in Part L 2006 were effectively unchanged from 2002, substantial improvements for 2010 are expected.

But what will these changes mean for glazing and windows? This question needs to be addressed in two parts, first for new buildings and secondly for replacement windows, because the Building Regulations approach their requirements in entirely different ways.

For new housing, Building Regulations are based on the total energy and carbon performance of the whole building, expressed as the CO2 Dwelling Emission Rate (DER). Part L 2010 will not require any specific performance of windows; just as the current 2006 Part L does not.

For existing dwellings and domestic-style buildings, Window Energy Ratings (WERs) became the main way of demonstrating compliance in 2006, with an E rating being required in replacement windows and D in extensions. It can be assumed that these levels will be increased in 2010, and that the intention is probably to move towards an A rating requirement in 2016. U-values are also an option for demonstrating compliance for replacement windows and windows in extensions under the current Part L. However, it is not known whether this will continue in 2010 because WERs, due to their more accurate reflection on energy performance, are regarded as superior and more reliable.

This is an important factor for window companies. The opportunity to sell windows that achieve higher ratings now, such as those containing Pilkington energiKare™, will continue to meet and exceed the requirements anticipated for 2010. In addition, those window companies that partner with us to supply Pilkington energiKare™ also benefit from the marketing campaign that is targeted at both homeowners and the trade. Window companies are able to use the respected Pilkington brand within their own promotion and branches, whilst also benefiting from supplying a brand that - thanks to television and regional press advertising in 2008 - is easily recognised by homeowners. An added bonus for suppliers is that windows incorporating Pilkington energiKare™ have the opportunity to receive accreditation from the Energy Saving Trust under its Energy Saving Recommended scheme.

The anticipated changes to Part L are good news for building designers and window/façade companies. They will create increased demand for higher performing products. The 2010 Part L will continue to take into account fully the positive energy benefits of glazing. This means moving away from the traditional fixation with U-values, with the full benefits of larger areas of glazing being recognised. Architects will see glazing in a new light and will no longer need to consider reducing the size of windows to tighten U-values. Clearly, reductions in window size are as unattractive to consumers as they are for architects and the window industry.

2010 is nearly upon us and the glazing industry needs to plan ahead to ensure they reap all the benefits of the changes to Part L - whether you are selling for new build, refurbishments or commercial buildings. To help architects, specifiers and the glazing industry get to grips with these changes, we have produced a guide entitled Bulletin 8 Part L 2010, providing information on the process, the timetable and the implications for windows and glazing.

To download a copy visit: or email