News analysis Building Regulations
Sucking the SAP from new Part L
The full details to Part L of the regulations are now out – or are they? Carina Bailey reports on a crucial missing link
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In the run-up to the general election last month, the
building services sector was waiting with bated breath for the key guidance to support the recent changes to Part L: the Approved Documents (ADs), compliance guides and the calculation methodology. Her Majesty’s Government had
issued statutory instruments to give legal force to these revisions – which take effect this October – but there was concern in the industry that the all-important ADs, which spell out the guidance, might not be published before a new government was elected. However, the Department
for Communities and Local Government did manage to publish the ADs before the election – and their arrival prompted a new set of concerns. The ADs were not accompanied by the national calculation methodology (NCM) – which is essential for designers to work out the emissions calculations to ensure their buildings meet the new standards demanded by Part L 2010 in terms of fuel and power. As the Journal went to press, the
NCM had still not been issued. David Kingstone, associate at engineering consultancy Buro Happold, says: ‘The most important document, the calculation
methodology, is still in draft form and subject to change. This needs to be finalised and published so that the software can be updated and approved, and assessors are able to study the new software prior to the October launch.’ Kingstone is also critical of the complexity of the methodology: ‘Some elements of the methodology are complex, and it may have been better to introduce an “energy consumption target”, as well as an emissions target, to deal with this.’ CIBSE member Peter Harris
believes the most fundamental change to Part L, though, is the difference in carbon factors (CF) between the 2006 and 2010 standard. Roughly speaking, a carbon (or emissions) factor is a relative figure that shows how much pollution is associated with a given activity. In the 2010 standard the CF for main gas, heating oil, wood pellets, consumed/grid electricity, and waste heat for district heating schemes per kgCO2/kWh have all increased – some significantly. For example, the CF of consumed
grid/electricity has gone from being 0.422 in Part L 2006 to 0.517 in Part L 2010 – making it 23 per cent worse in terms of carbon emissions. This has serious implications for some technologies, such as air source heat pumps (ASHP), making them
Proposed changes to carbon emissions in Part L 2010 against Part L 2006
Fuel
Mains gas Heating oil Wood pellets
Consumed electricity Displaced electricity
Waste heat for district heating systems
2006 kgCO2/kWh 2010 kgCO2/kWh Change
0.194 0.265 0.025 0.422 0.568
0.198 0.274 0.028 0.517 0.529
0.018 0.058
+2% +3%
+12% +23% –7%
+322%
Plus sign indicates a worse factor, minus sign a better one
Source: Department for Communities and Local Government/BRE
The calculation methodology is still subject
to change, but it needs to be finalised in time for the October launch – David Kingstone
less attractive to designers because, from October, they will be deemed to emit more carbon. The same will also be true for waste heat for district heating schemes, which has jumped from 0.018 per kgCO2/kWh to 0.058 per kgCO2/kWh – a threefold rise in carbon emissions. Harris explains: ‘The significant
shift in the grid electricity from 0.422 to 0.517 will raise a lot of eyebrows. Does this mean that the national grid is getting worse? If so, is it right that developers are having to spend tens of millions of pounds improving the energy efficiency of buildings by 25 per cent, or to provide a 20 per cent on-site renewables contribution, when the national grid cancels this out by getting worse by 23 per cent? ‘It will be interesting to see, now,
whether more schemes promote the use of on-site combined heat and power (CHP) for cooling as well as heating.’ He adds that the same will be true for ASHPs: ‘With only a two
16
CIBSE Journal June 2010
per cent increase in the CF for gas and a massive leap of 23 per cent for electricity, does this now begs the question whether ASHPs can provide significant carbon savings?’ Kingstone adds that the change
in the way fan and pump emissions are calculated will mean that energy performance assessors will have to reconsider how the emissions will influence system design selection. ‘Although the definition for the Energy Performance Certificate (EPC) reference building has not changed, the way emissions are calculated for an actual building have. This will mean that the resulting EPC rating, assessed from October, will be different to that calculated now. ‘This may result in a change in
the EPC rating band, the number of BREEAM energy credits and even the BREEAM rating. However, only by assessing this in detail, and on a range of building types, will the result be known.’ But what does this mean for
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