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(ACDs), or better still, Enhanced Construction Details seen many self-build projects incorporating renewables
(ECDs). These are fairly simple ways of reducing for a number of years, they will become much more
the transfer of heat out of the dwelling and make a mainstream.
significant improvement in SAP results. There are also lots of proposed changes to the way
Our experience is that many developers are not new houses are actually assessed through SAP. The
aware of ACDs but, in fact, already incorporate many way it’s set up at the moment, it is much more difficult
of the requirements to reduce the likelihood of thermal for a small flat, for example, to achieve a 25 per cent
bridging. It is likely that the proposed changes next improvement compared with a large detached house.
year will require developers to actually prove they This is mainly due to the fact that flats are already
have reduced thermal bridging. Further information inherently energy efficient, leaving less room for
can be found on the Planning Portal website (www. improvement. The government proposals will hopefully
planningportal.gov.uk). remedy this anomaly.
Air leakage testing of new buildings has been a At present, party walls between dwellings are
Building Regulations requirement since 2006, and we not accounted for in the energy calculations as it’s
are discovering that the vast majority of our clients find assumed both properties are heated to the same level
it fairly easy to meet the basic requirements (achieving and therefore there is no heat loss. However, research
about a 98 per cent pass rate). Next year’s requirements, has shown that there can be a significant amount of heat
however, will encourage house builders to not only loss through the cavity of a party wall, and this will have
meet the regulations but to significantly improve on to be accounted for.
them by reducing air leakage to levels below 5cu m/ The ‘fuel factor’ may also be eliminated in next year’s
sq m.hr@50Pa. This would represent a 50 per cent assessment process, which at present makes heat
improvement in today’s maximum leakage rate. pumps an easy way of achieving a 25 per cent efficiency
With low air leakage rates comes potential ventilation improvement. At present, lower fabric standards are
issues, and Building Regulations may require houses required for dwellings with electric heating systems
to be built to very airtight standards to incorporate compared with gas and oil, and this may be tightened to
mechanical ventilation systems with heat recovery. It’s bring the various fuel types more in line with each other.
also likely that a higher proportion of low-energy lights The proposals to amend Parts L and F provide further
than the present 25 per cent will be necessary. For those challenges to house builders in the drive to reduce energy
not keen on the compact fluorescent types, LEDs offer use and emissions from new homes. Those working in
an alternative, low-energy solution. this sector will need to keep up with proposals over the
Finally, on a number of new houses, low or zero-carbon next few months. l
technologies could be needed to help achieve the 25 per
cent carbon emission improvement. Solar panels, heat
Alex Hole is the managing director of Midland Energy Services.
recovery systems, biomass boilers and heat pumps will
www.midlandenergyservices.co.uk
all start to appear more regularly. Although we have
www.cibsejournal.com November 2009 CIBSE Journal 49
CIBSEnov09 pp48-49 new homes.indd 49 22/10/09 17:15:48
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