A focus on building fabric instead of renewables is the most cost effective approach for housing, says Mel Starrs
By far, the most exciting aspect (if there can be said to be one) surrounding the Part L 2013 consultation is the Green Deal, consequential improvements and Part L1B. However, for the new build housing sector there is still quite a bit to get to grips with, particularly for anyone in the private market who has yet to encounter FEE (fabric energy efficiency).
On first sight, the headline figure of an 8% carbon improvement over 2010 levels for the government’s preferred route may not sound particularly taxing, but there is a quantum shift in focus towards a fabric first approach.
There will be a shift in capital spend in housing away from renewables towards fabric, with a concurrent up-skilling of the industry
The drivers for this are, typically for the times we live in, economic. Renewables, while effective at reducing carbon, are too expensive for housing in these straitened times, as demonstrated by the impact assessment which accompanies the consultation documentation. Rather than setting a 25% target that would render many housing developments uneconomic, DCLG are pushing the fabric to close to the limits of diminishing returns. This is a significant step towards zero carbon.
Fabric first is a mantra the industry has been trying to follow for years, which makes sense given one would hope the fabric is generally around for the equivalent of several lifetimes of technologies. So why have we not been able to follow a purely fabric first approach up to now? The tension between fabric and renewables in recent years has been driven by concurrently trying to meet the parallel, but often contradictory requirements of both the planning and building regulations systems.
‘Merton’-style planning requirements, which incorporate the requirements of Planning Policy Statement 22 (PPS22) to use on-site renewable to deliver 10% or 20% energy or carbon reductions, have been competing with the needs of meeting Part L 2006 or 2010. Part L was left flexible enough to allow a balance of renewables and fabric and whereas the most cost effective approach may have been fabric first, the renewables targets typically ‘won’ a chunk of the capital cost. Fabric would typically be designed up to that point where adding the required renewables percentage met the target for compliance with building regulations. The renewables contributed to local, regional and national targets and to the overall goal of reducing carbon by 80% by 2050.
Concentrating on fabric should also begin to alleviate one of the factors in the design-performance gap
The move towards a fabric first approach in Part L 2013 is set in the context of the long awaited National Planning Policy Framework (NPPF). As of 1 April 2012 PPS22 will no longer be current and local plans which have been developed with ‘Merton’-style rules will have to prove the viability of such approaches.
The proposed standards are buildable today – we are seeing some schemes, especially mid-rise apartment blocks in London where Greater London Authority (GLA) have been demanding compliance to Part L 2010 through energy efficiency alone, meeting and exceeding these targets already.
What will this mean in practice? Adherence to the fabric performance holy trinity of increased U-values, attention to thermal bridging and increased air tightness. There will be a shift in capital spend in housing away from renewables towards fabric, with a concurrent up-skilling of the industry, as we endeavour to build the most efficient dwellings we possibly can. Concentrating on fabric should also begin to alleviate one of the factors in the design-performance gap.
It’s not all doom for the renewables sector though - the accompanying preferred route for Part L2A for non-domestic building of 20% finds renewables are a more cost effective route than fabric for this very broad sector. Presumably this is due to typically larger volume to surface area ratios, where we meet the point of diminishing returns on fabric earlier.
Mel Starrs is associate director at PRP Architects