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What Part L means to you

Revisions to the building regulations will create new challenges for the hvac industry, writes James Boley.

The end of April saw the release of the revisions to Pa rt L Building Regulations for 2010. Covering both dwellings and non-residential buildings, the regulationsstrengthen existing ones dealing with the conservation of fuel and power.

The revisions to Part L are part of a process that began in 2002. Last revised in 2006, the 2010 revisions will be introduced in October and last until 2013, when they will be revised again as part of the government target for all new buildings to be zero-carbon by 2020.

Towering over all parts of the regulations is the requirement for buildings to cut their carbon emissions by 25 per cent relative to a comparable building built according to the 2006 regulations. As a result, focusing on carbon reduction has become even more important.

However, how this requirement should be achieved varies between types of building. While domestic buildings must have an absolute reduction of 25 per cent, non-domestic buildings will be calculated on an aggregate approach.

What this means in practice is that across all non-domestic buildings there should be an overall reduction of 25 per cent. Therefore, some non-domestic buildings will have a lower target to reach than 25 per cent, while others will have higher targets.

Aecom director of sustainability Ant Wilson says: “It’s based on neutralising the abatement cost of achieving the target. If it would cost you more to do it on one type of building, you might only need a 20 per cent improvement instead of 25 per cent. If it’s cheaper, you might need a 30 or 35 per cent improvement.”

He explains that the system has been designed to make it fairer on all development so that particular industries are not unnecessarily penalised. “It’s still not 100 per cent fair but it takes out the extremes,” he says. The exact ratio of targets has yet to be determined.

“The measures contained in Part L will have a major impact in reducing carbon emissions on new and existing developments with effect from October this year,” said Baxi Group’s channel specification manager Simon Osborne. “They clarify the requirement for higher efficiency boilers and hot water storage vessels in
dwellings.

“They will also provide a boost for the wider adoption of LZC (low and zero-carbon) technologies, including micro-CHP solutions such as Baxi Ecogen, ground and air source heat pumps, biomass and solar panels”.

Before starting on site
One of the crucial ways in which the revisions will change the delivery of buildings is through the approval process. Association of Consultant Approved Inspectors
chairman Nigel Barr says: “One of the main issues is [building inspectors] are now asking for TER and DER calculations prior to the commencement of the work.”

He says this will particularly affect flat developments. “On larger developments, inevitably they’re starting on site prior to finalised designs being put in place. So you have the shell design, but the individual flats generally wouldn’t be finalised until after the frame has started.

“The potential there is that building control will be asking for the calculations, but developers and contractors may not have those details available. That’s a potential and unnecessary conflict area. That hasn’t been standard practice before,” he says.

As a result, he recommends contractors start liaising closely with building control bodies so that both sides understand the level of information they can expect from each other. “They will need to come to an agreement as to what is an acceptable level of information. I would hope building control bodies would be understanding of the restrictions placed on contractors in getting that information, and look at staged approval,” says Mr Barr.

Getting these sorts of approvals sorted out early on could in fact prove to be a positive step, according to Inbuilt service co-ordinator Mel Starrs. “Submitting a
design stage certification has previously been good practice, but that will now be a requirement. That’s a good thing for contractors, as that certification should exist before they get on board, so they can be more certain as to what the final building should be,” she says.

Once at work
Having begun on site, companies will find their work subject to more rigorous testing than they may have been used to previously, particularly when it comes to air
pressure testing. “The volume of pressure testing required will roughly double. A pressure test should be carried out on three units of each dwelling type or 50 per cent of the instances of the dwelling type, whichever is the smaller,” says NES technical manager Dyfrig Hughes.

“In addition, a confidence factor will apply to dwellings not pressure tested. Where a dwelling has been pressure tested, the measured value is used in the calculation of the DER. Where the dwelling has not been pressure tested, the value used in the DER calculation is the average of the measured values for dwellings of the same type but with the addition of a confidence factor of 2 cu m/(h.m2) at 50 pa.”

Aecom’s Ant Wilson points out that a subtle wording change in the 2010 revision will also place the onus on the contractor to refine the efficiency of the project during construction. “The old wording was that you had to provide and commission efficient energy services with effective control,” he says. “It now says you have to
provide fixed building services which are energy efficient, have effective controls and are commissioned by testing and adjusting as necessary to ensure they use no more fuel and power than is reasonable in the circumstances.”

Contractors will also need to keep a close eye on their subcontractors to ensure any of their work doesn’t disrupt the project’s ability to meet the regulations. “Subcontractors will need to be aware of the implications of their actions on site which could have an impact on those final figures,” says Mr Barr.

“It’s fine designing walls or roofs to comply with Part L and have that as part of the design stage calculations. But if a subcontractor comes along, they might do something like knock a hole in a wall or alter the insulation, which might have an impact on something like the pressure test.”

A growth in renewables
The new targets set in Part L also mean that contractors will likely have to improve their knowledge of installing renewable energy sources. “It’s just about possible to
meet the 25 per cent reduction target through optimising the fabric and air permeability,” says Ms Starrs.

“However, I suspect we’ll be seeing more renewable energy sources included in projects in order to meet the target.” She also points out that Part L will be revisedagain in 2013 and will carry an even higher required carbon reduction - so it makes sense for contractors to start looking at these elements now while they are less
demanding.

However, changes in the way the way reductions are calculated in comparison with the notional building mean that renewables will need to be considered far more carefully. Previously, the impact of adding renewable energy sources to a project was unfairly calculated, as it was not on a like-for-like basis.

“Previously, if you were putting in a biomass boiler, you’d be comparing it with a gas-powered notional building. Under the 2010 regulations, you’ll be comparing it with a biomass-powered notional building,” says Ms Starrs.

Essentially, this means designers cannot do something like put a few PV panels on top of a building and then claim the building is more carbon efficient. Instead, the
application of renewables will need to thoroughly evaluated, and contractors should ensure they fully understand each method in order to maximise the benefits.

As already indicated, the regulations are likely to change again and become even more rigorous in 2013. With a change of government, it remains to be seen whether this policy will continue. However, some experts warn that contractors should bear in mind that future projects may be subject to more stringent requirements, so there may be value in ‘over-designing’ to anticipate these possible changes.

“Firms planning big developments should be looking even further ahead. If you’re doing a massive estate, you should already be thinking about zero-carbon homes,”
says Mr Wilson.

Similarly, Ms Starrs says: “Say you’re working on a project that comes under the 2006 regulations. Your next one will come under the 2010 revisions. It’s conceivable
your next one will be under 2013.”


Not all projects will be required to comply with Part L 2010. Although the regulations come into force in October, a phased transition period means that some
projects will only need to comply with the 2006 version.

  • If you’ve already started on site: the 2006 regulations will apply indefinitely to your project;
  • If you’ve yet to start on site but plans have been submitted and approved: the 2006
    regulations apply indefinitely, provided you start work within a year;
  • If you’ve yet to start on site but plans have been certified and accepted: the 2006
    regulations apply indefinitely, provided you start work within a year;
  • If you’ve yet to start on site and full plans aren’t required (the Building Notice route):
    the 2006 regulations apply indefinitely, provided you start work within six months.
    is my project covered?

Where to get documentation

Part L contains four approved documents:

  • Approved Document L1A: Conservation of fuel and power (new dwellings)
  • Approved Document L1B: Conservation of fuel and power (existing dwellings)
  • Approved Document L2A: Conservation of fuel and power (new buildings other than dwellings)
  • Approved Document L2B: Conservation of fuel and power (existing buildings other
    than dwellings)
    The documents are available online at http://snurl.com/partl2010