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 Part L consultation document was published, much has been written about the impact
of the proposals on current building practices. Now is the time to assess their full implications
in a calm and rational manner. Two things so far have 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.
The major Aircrete manufactures are currently advising housebuilders to contact them for dependable,
practical advice on how to meet the new energy regulations. To support this, the APA
(Durox, H & H Celcon, Tarmac Topblock and Thermalite) has produced a Guide to the Consultation Document,
detailing the main issues contained within the proposals and their collective advice on how to comply
with the changes.
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