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The Future for Part L

24 January 2011

As the first decade of the new millennium draws to a close, it is becoming clear that 2010 will be an important year for the construction industry. It marks the date when the latest changes will be made to Part L of the Building Regulations for England and Wales. 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.  New dwellings will require energy and carbon reductions of 25 per cent by 2010, 44 per cent by 2013 and 100 per cent by 2016. For non-dwellings, it is likely the Department will insist on the same improvement levels as for dwellings in 2010 and 2013, delaying zero-carbon standards until 2019.

However, 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, which means that 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 from 2010 onwards are expected. This had already led forward thinking developers and architects to incorporate the substantial benefits of triple glazing into new, lower carbon properties – thus often offsetting the need to invest in costly renewable technologies.  As the regulations tighten, in new homes at least, the move to triple glazing, as in much of continental Europe, is inevitable – still optimising both thermal insulation AND passive solar gain benefits.

For existing dwellings and domestic-style buildings, Window Energy Ratings (WERs) were a 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 (expected to be a C rating for both), and 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. For a further period at least, window U-values will remain as WERs become more established and accessible to all.   Centre pane U-values however, a poor indicator of total window energy efficiency, are likely be an allowable demonstration of compliance only for historic buildings, where choice of frame design is severely restricted.

Another likely key change is a move to bring all domestic conservatories under Part L.  In respect of glazing, the proposals are effectively to mandate low-E throughout vertical glazing and any glazed roofs.  Additionally, to offset the need for increased air conditioning and net carbon emission from the home, solar control will be stipulated in certain aspects of the conservatory.  So for all roofs (polycarbonate or glazed) there will be solar control implications; ruling out single and basic modern double glazing for good.  Additionally, in south- facing conservatories, the vertical glazing elements will also be required to have enhanced solar control properties.

Building lifecycle costs are also an important consideration and any reduction of natural light means money and energy must be spent on artificial lighting and heating and cooling; an unsatisfactory, environmentally-unfriendly and costly alternative to managing the sun’s free heat. These considerations have been endorsed in a recent study by Glass for Europe, the trade association for Europe’s manufacturers of flat glass, which reveals how high-performance solar control glazing can help contribute to carbon emissions savings.  Taking into account a ‘business as usual’ growth in the use of air conditioning systems to 2020, the possible CO2 savings through the introduction of solar control glazing are as much as 1,097,000 tonnes, a saving equivalent to 9.3 per cent of the UK’s CO2 emissions. The study clearly demonstrates that high performance solar control glazing will be an important aspect in the future of commercial buildings.

The changes to Part L will have repercussions throughout the industry. The anticipated changes are good news for building designers and window and 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 recognised. Architects will see glazing in a new light and will no longer reduce the size of windows to tighten U-values.

To help architects and specifiers get to grips with these changes, Pilkington has 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: