Casting a block vote

Press coverage of the proposed changes to Part L of the Building Regulations has caused considerable disquiet among housebuilders and specifiers, which are alarmed at the prospect of having to change their construction methods. This will not have been helped by reports of the DETR’s supposed determination to accelerate the use of timber frame in housebuilding and suggestions that the Part L changes are bad news for block manufacturers. Nothing could be further from the truth on these two points.

On the first, the DETR has recently reconfirmed its official rebuttal of any implied support for one method of construction over another. This is a consultation process, not a directive.

Second, there is simply no substance in the suggestion that aircrete masonry will not be able to meet the proposed upgrading of U-values. How this misconception has come about is hard to imagine. Aircrete accounts for about 70% of all new houses – and for good reason. In the UK, as in the rest of Europe, most are built with this type of block because it is the most cost-effective. It is also easy to build with, versatile and, not least, thermally efficient. It is therefore difficult to understand how concerns could have arisen over its ability to meet tighter U-values.

For the record, not only can the proposed changes be met using aircrete, but this method will continue to be better value than frame construction. The proposed changes can be met using existing designs and construction details with minor modifications and without the need for thicker walls. What is more, aircrete is “Egan-friendly”; it provides innovative solutions such as the rapid-build thin-joint system, it uses widely available skills, results in minimal waste and gives homeowners what they repeatedly say they want: solid masonry constructions. These are just some of the reasons that the proposals are more likely to result in an increase in the use of aircrete rather than a decline.

Not only can the proposed changes be met using aircrete, but it will continue to be better value than frame construction

Initial reaction to the proposed Part L changes focuses almost universally on the elemental approach to compliance. This is the least used method and the least sophisticated, in that it simply measures heat loss through each part of the fabric, such as roof, walls and so on. So why the sudden popularity?

One reason is its simplicity: “U-value reduced to 0.35 W/m2ºC” may seem easier to grasp than more complex assessment methods – even though, for the majority of housebuilders, these are more familiar. In fact, the proposed changes retain the three existing ways of checking compliance: elemental; target-U and SAP (now replaced by carbon index), but give strong support for the latter two.

The reason for this is that they are inherently more effective ways of reducing carbon dioxide emissions; they take into account the efficiency of heating systems, solar gain and so on, and provide greater flexibility in the choice of windows and doors. They also, arguably, represent a more responsible approach to energy saving by encouraging comprehensive improvements across all elements.