Approved Document L of the Building Regulations is currently under review, focusing not just on improvements to individual components but on the building as a whole.

Roughly 46% of the UK's Carbon Dioxide (CO2) emissions are produced by the energy consumption of buildings, including the operation of associated building services. This is an area where new legislation can have an impact, and consequently, these pressures have filtered through to those sections of the national building regulations that deal with the Conservation of Fuel and Power. For England and Wales this is Approved Document 'L' of the Building Regulations and for Scotland: Technical Standard J of the Building Standards.

In arriving at the amendments the following important areas were considered;

• Reduction of CO2
• To retain or improve design flexibility
• Reduction of Technical Risks
• Avoiding excessive costs

• U-values for all building elements have been reduced.
• The method for calculating U-values has changed. This means that, for the same construction, a slightly higher (worse) value is produced.
• Tighter control of heating and hot water components and commissioning of these systems.
• Boiler efficiency is now an integral part of all methods of compliance.
• Improved guidance on the control of air leakage and cold bridging outlined in a separate document, providing robust construction details.
• Measures included addressing the overall performance of heating, lighting, air conditioning and mechanical ventilation systems.
• New requirements for both internal and external lighting.

Following a period of consultation ending in October 2004, this Regulation is now being amended and it is anticipated will come into effect January 2006.

Using the Calculation Methods of compliance means that tried and tested forms of masonry construction will continue to be used to meet the higher overall standards as proposed in Part L.

Since June 2000, when the first Part L consultation document was published, much has been written about the impact of the proposals on current building practices. Two things tended to characterise the debate - an emphasis on compliance with the lesser-used 'Elemental' approach and the heralding of the death of aircrete block construction due to its alleged inability to meet the proposed changes. The first argument is seriously misguided and the second is patently untrue and ill-informed.

The APA, representing all major aircrete block manufacturers, supports the DETR's proposals to improve energy efficiency of all new construction, and it especially applauds the approach for assessing the energy performance of a building as a whole, rather than concentrating on single elements.

The primary objective behind the Part L proposals is to improve whole-of-house energy efficiency as part of the government's commitment to reduce carbon dioxide emissions. Despite this, many reports have centred solely on the external envelope and in particular, wall U-values. To assess the whole picture, other factors have to be taken into account, such as heating systems, lighting and air infiltration, and as with the current Regs, three methods of compliance are allowed, elemental, target U-value and carbon/energy index.

The elemental approach of compliance has dominated the Part L discourse, when ironically, it is the one method least favoured by housebuilders.

It is true that the elemental route has a simplicity of approach, but it is best suited for smaller ad hoc projects, such as extensions. For the larger housebuilder, however, it is too restrictive and inflexible. It is also important for housebuilders to note that a SAP rating is still required when using this approach, just as it is with the Calculation Methods. The latter however, allows for greater design versatility and will typically produce a more cost effective solution, consequently, there is a compelling case for designers and builders to consider this option. Ultimately, the Calculation Methods of compliance mean that tried and tested forms of masonry construction will continue to be used to meet higher overall standards. These solutions are still available using one of the many insulation materials currently on the market in combination with aircrete masonry.

The holistic energy equations used in the Target-U and Carbon Index methods are more energy efficient, and arguably, represent a more responsible approach to energy saving by encouraging comprehensive improvements across all elements.

A lot of fuss has been made of the proposal to reduce wall values to 0.35w/m2K, but the truth is that many existing masonry construction practices already meet the proposed new standards, despite reports to the contrary. Where they do not, it is in many cases possible to make simple changes to the type or depth of insulation used, without the need for altering the actual construction. Aircrete is a structural material that has an inherent thermal efficiency, and as such it provides a significant proportion of the insulation needed to achieve the increased performance requirements within the Part L proposals.

Aircrete allows for both full or partial fill insulation without necessarily increasing cavity widths - a primary concern for builders seeking to maximise liveable space within the building footprint. The proposed regulations will, in the majority of cases, allow the continued use of existing wall constructions with minimal modifications and the Part L requirements will continue to be achieved more cost effectively with aircrete masonry construction than with timber or steel frame. Aircrete masonry construction currently accounts for around 70% of all new housing and the proposed new regulations will, if anything, consolidate this position. In addition to its energy efficiency, Aircrete also fulfils many of the Egan principals.

Aircrete manufactures advise housebuilders to contact them for dependable, practical advice on how to meet the new energy regulations.

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