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Part L 2010 Consultation – Final thoughts

by Mel Starrs on September 17, 2009

in Part L

Had I realised the 17th was not tomorrow, but today, I might have been able to construct a more considered piece. For completeness, here are some further rambling thoughts on the Part L 2010 consultation. Issues I wanted to look into further but ran out of time on included overheating, and a better understanding of the numbers involved in L2A vs. L2B.

Not discussed at the Sponge event, but will be of interest to some will be the proposed approach of aggregating the percentage improvement over building types (for non-domestic), rather than a flat 25% improvement over the 2002 notional building. This means that averaged over the building stock, a 25% improvement will be made. Whilst I applaud the logic, the ‘black box’ aspect of applying these curves, plus questions over what happens if the predictions are wrong (i.e. the mix of building works changes dramatically over the period of time the curves are supposed to work) mean I am not entirely happy with this. I agree it’s probably more sensible than the flat approach for non-domestic stock, but are we approaching the problem correctly in the first instance?

Are the goalposts changing? Are we still comparing to 2002 notional building? Or was the 2002 notional building never the right building to compare against in the first place? The answers are, yes, no, probably not. Part L 2010 is an improvement on 2006, but an improvement to a less than ideal solution to begin with.

There are some who think that SBEM should never have been introduced and that a DSM approach (perhaps based on the open-source US DOE program Energy Plus, which was once the basis of IES) should have been employed as the only non-domestic solution from the outset. Are SBEM’s days numbered? I’m not sure – I haven’t managed to find out figures for numbers of buildings submitted using SBEM vs. DSM over the last 4 years (I feel a request for information under FOI coming on), but I personally am much happier using proprietary DSM software than SBEM, even if the building templates have largely been slim-lined and rationalised for 2010.

Ex-colleague Lynne, over at Hattie’s blog says:

In the Part L consultation, reinforced by the Zero Carbon Definition response from government, a clear emphasis on reducing demand through building fabric is made explicit in the guidance, although as yet the proposals are not prescriptive via U-values and the principle of design freedom is maintained.

As an architect, what is clear to me is that we need to gear our design development process to understand the impacts of what we draw from day one – in Part L and F terms, this means getting orientation, fenestration, construction typology and solar access right so that we are using the ‘basics’ to minimise demand as far as possible from the very outset.

Part L 2010 still gives designers some degree of discretion, rather than dictating a ‘cookie-cutter’ solution. Simplified and arbitrary targets (and yes, I am having a dig at Passivhaus here) devalue and marginalise design engineers. We cannot allow this to happen. Defending discretionary behaviour should be the rallying call of CIBSE, IStructE and others, improving the profession’s standing in the UK (which we cannot allow to be subjugated any further).

There was a puff piece some time back in the AJ, where the Tories rather jokingly wanted to abolish Building Regulations. Let’s not throw the baby out with the bathwater, but rather than tie ourselves in knots trying to meet arbitrarily set targets, let’s get back to first principles and remember what the intentions of the Regulations are:

  • conservation of fuel and power
  • predicting carbon emissions and ensuring they are less than a stated minimum

It is well within our ken to apply our minds to these riddles, retaining design freedom and without getting lost in a mire of red tape. Isn’t it?