Is there life after Part L?
In March, our panel of experts answered your Part L questions. Four months after implementation, Elaine Knutt asks architects how Part L is affecting their work
What impact is Part L having on buildings’ design and appearance?
A noticeable one, by all accounts. BDP has submitted schools, office and housing projects under the new regulations, and sustainability director Trevor Butler says that the result of its in-house Part L compliance checklist has been substantial design changes. “People had to do things they wouldn’t have done previously. Windows either got smaller, or were shaded, or we changed the glass specification,” he says.
At Reid Architecture, technical manager Stuart Barlow conducted an experiment by inputting the data for a 7,000sq m office completed four years ago into the SBEM calculation tool. It failed, with energy loads for
heating and cooling substantially too high. “Even after adding improvements to the services and controls, we’d have had to change the form and appearance [of the facade],” he concluded.
Has Part L compliance led to project cost increases?
The general consensus appears to be yes. The basic improvements in the fabric often necessary to achieve compliance — such as improving the glazing specification, windows, quality and thickness of the insulation — are adding 1-2% to capital costs. And as projects progress it will be far harder for clients and consultants to drop sustainable features in the name of “value engineering” — further inflating the final account.
“We’ve come across a number of cases where budgets haven’t been sufficient to meet Part L,” says Peter Karabin, divisional director for building services at Peter Brett Associates. A specific example from PRP’s Mike Piraulx is a block of flats where the developer had to bear the extra cost of heating communal areas in order to comply with Part L.
Are designers getting to grips with the SBEM calculation tool?
The most frequent complaint about SBEM and the authorised independent systems — including Virtual Environment by IES and TAS from EDSL — is their lack of transparency. “It’s like putting numbers into a black box,” complains Max Fordham partner David Lindsey. “You put the data in and get a pass or fail answer — and you don’t quite know why. Buildings might comply, but the system can’t tell you whether you’ve got the best solution.”
And neither SBEM nor the proprietary software allows designers to offset the energy generated by renewable technologies against carbon emissions in a single integrated calculation.
Overall, architects wish SBEM was more user-friendly. Dividing the building into the requisite “zones” then entering all the required data for the exemplar office scheme mentioned above took Reid Architecture’s Stuart Barlow three to four days.
Prior to April 1, there were fears that it would be harder for naturally ventilated buildings to comply with Part L than air-conditioned ones. Has this proved the case?
The regulations expect air-conditioned or mechanically ventilated buildings to achieve a 28% reduction in carbon consumption relative to Part L 2002, while naturally ventilated buildings have a target of 25%. But while it’s relatively easy to gain efficiency improvements in the plant room, the changes to the fabric needed to cut consumption in naturally ventilated buildings are costly and complex.
BDP’s Butler fears that this is encouraging PFI consortiums in particular to go for more straightforward mechanical solutions on the next generation of schools and hospitals. “It’s good to focus people on low energy, but what about user comfort?” he asks.
On the other hand, it could encourage designers to explore new natural ventilation tools. “We’re looking at ground coupling [where supply air passes through buried tubes] to get about 6°C of free cooling,” he says.
But one practice, which has yet to make a Building Control application or try an SBEM dry-run, told BD confidently its higher education building was bound to pass “because it’s naturally ventilated”. When the above situation was outlined to them, there was an awkward silence on the line.
Part L 2006 introduced the airtightness test for dwellings. Will this lead to a generation of airtight but lightweight buildings prone to overheating?
It’s certainly a concern at architect Feilden Clegg Bradley. “Developers can’t see their buildings meeting airtightness tests without off-site construction, so it’s prompting them to use Structural Insulated Panels and other MMC approaches,” says partner Bill Gething, who is also RIBA adviser on sustainability. “The conundrum hasn’t been solved, and I don’t think there’s been enough work done on getting the right level of thermal mass in houses.”
As for the risk of light-weight apartments over-heating, PRP environmental adviser Mike Priaulx has come across examples when the assumptions needed to meet Part L requirements on this point included keeping the curtains closed on sunny days.
How are Building Control officers coping with the new Part L?
Will Building Control officers have the training to check assumptions behind the Building Energy Rating, or will applications just be rubber-stamped? And how thoroughly will they check that as-built buildings match the design specification?
On both points, there seems to be as many answers as there are Building Control departments. “Each local authority will take its own view,” says Paul Everall, chief executive of Local Authority Building Control. “As they become more experienced, officers will get a feel for what to look for in relation to Part L 2002.”
As for the as-built tests, Everall says: “I think they will be robust. Building Control officers can ask for items to be installed or replaced, and if they’re not satisfied, a completion certificate won’t be issued.”
And what about all-electric buildings — often seen as the safest and cheapest design option for heating student residences and key worker flats?
When Keith Hayday of Maber Associates raised the issue with our Part L panel (Solutions, March 31), the response was that installing individual gas boilers could be avoided if the development as a whole also incorporated centralised heating or solar thermal systems. Fine in theory, but not in the social housing world of tight budgets and time frames, and limited experience of renewable energy technologies.
“The penalties for using electric mean that people are going back to gas,” Hayday says. “Yes, there’s the cost of additional ducts and designing the flats so that the boilers are mounted on outside walls, but it’s still less costly than electricity plus other provisions, especially if people haven’t worked with them before.”
So, in at least two Maber Associates projects, the unintended consequence of Part L will be to expose low-income tenants to the financial pain of rising gas prices.
Is Part L accelerating the take-up of renewable energy technologies?
On major residential and mixed-use projects, the answer seems to be yes. “There’s a really big swing towards combined heat and power, district heating and site-wide generation of power,” says Henrietta Lynch, a sustainability consultant at BDP. “With the rising cost of energy, generating it on site can work out cheaper, and it helps get the scheme through planning.”
That’s the key point: it’s hard to disentangle the effect of building regulations and the effect of local authorities’ adoption of the Merton Rule, whereby major schemes will only be granted planning permission if they generate 10% of their energy needs via renewables on site.
Paul Appleby, head of sustainability at engineering consultant URS, adds that local authorities’ clout “gets stronger the closer you get to London”. But he says that large-scale take up of CHP is inhibited by the fact that locally generated electricity cannot be sold back to the grid. “It happens in Germany, and would make a big difference here.”
What hidden consequences of Part L are emerging?
Architects are just realising that designing buildings under Part L 2006 requires much more forward thinking at a much earlier stage. Whereas decisions on the power of the fan units or the efficiency of the pumps could once be left until detailed design, they are now needed pre-planning. As the contract moves ahead, everyone will need to focus on Part L. “What about value engineering? What if the concept architect doesn’t do the contract documentation? There’s a lot of joining up to do,” says Butler.
Max Fordham is among services consultants finding that Part L has boosted its fee income. “There’s more incentive for us to be brought in at an earlier stage,” says Lindsey.
So, has it all been worth it?
Part L will undoubtedly shrink the difference in performance between avowedly green “best practice” flagships and the main flotilla of the industry. “Systems designed badly will fail, so it raises the standard to a level of good practice across all projects,” says Lindsey.
But is all the extra effort, expense, design time, re-design time, capital costs and general upheaval really worth a 25% carbon reduction relative to fairly exacting 2002 standards? Put that question to a panel of Pacific islanders, Inuit hunters, Alpine villagers and others directly affected by climate change, and the answer would be yes.