New buildings in the UK are supposed to be energy efficient, but the regulations intended to achieve this outcome secure efficiency in theory, but not always in practice. With operational energy performance rarely measured, this failure has been invisible, leading to the ‘performance gap’ between original design intent and how a building performs in use.
Design for Performance (DfP) is an industry-funded and backed initiative, established to tackle the performance gap and create a building-rating scheme based on measurable performance outcomes. The project looks to emulate the Nabers Energy Rating and Commitment Agreement that has transformed the prime office sector in Australia.
What is Nabers?
Australia’s Nabers office energy-rating scheme targets in-use energy performance of the ‘base building’ – services typically under the control of the property owner, including heating, hot water, ventilation and air conditioning of the whole building, light and power in common areas, and lifts. For new office developments, clients, developers and their teams sign up to – and follow – a ‘Commitment Agreement’ to design, construct and manage buildings to achieve agreed levels of in-use performance.
‘This is not a “nice to have”,’ says Sarah Ratcliffe, chair of the DfP executive board, and programme director at the Better Buildings Partnership. ‘The UK property industry desperately needs verification and disclosure of performance in use because, without these, the market cannot drive improvements in performance.’
Ratcliffe says the UK has been largely operating under the false impression that its regulatory and voluntary standards give a good indication of performance. ‘But these standards measure only design intent, and buildings’ actual performance is invisible,’ she adds.
Currently, no metric exists to give the market visibility on performance, says Robert Cohen, technical lead at DfP, and technical director at Verco Advisory Services.
‘Whether one building is better than its peers is unknown – the market is operating completely blind.’
Cohen says DfP is attempting to replicate what Nabers has done in Australia, where disclosure of the measured, base building operational rating is mandatory for commercial offices. In the UK, buildings must disclose their Energy Performance Certificates (EPCs), but these are based on theoretical calculations.
Design for performance timeline
In 2012, Verco worked with the Better Buildings Partnership (BBP) to develop a Nabers-like ‘landlord energy’ rating scheme, which was piloted on 85 BBP members’ buildings. It was found that applying the Nabers system to existing offices in the UK was a challenge because it was either too expensive or inaccurate. ‘We needed to know how much energy was used for the HVAC throughout the building over a year,’ says Cohen, ‘but the landlord was only able to tell us the energy used for the central system and, often, this was supplemented by energy use from the tenants’ supplies – for example, for fan coil motors or perimeter heating.
These HVAC energy uses could not be disentangled from the energy used by tenants for their lighting and plug loads.’As a result, DfP looked at creating the scheme for new buildings, where the ‘blurred lines in metering and building services arrangements can be avoided because you’re starting with a clean sheet of paper’, adds Cohen.
In 2015, DfP ran a six-month desk feasibility study, looking at key components of the scheme with Australian experts and checking whether they could work in the UK, particularly for new developments. The pilot projects – completed over the past two years – then tested whether or not it was possible in actual office developments.
Last month, DfP announced the ‘pioneers phase’, which involves the development of a national Nabers-like scheme in the UK.
After a feasibility study and a series of pilot projects (see panel, ‘DfP timeline’), the DfP team has secured the commitment of seven ‘pioneer’ developers to fund the establishment of a Nabers-like scheme and apply the Commitment Agreement process to at least one of their projects. They include: Landsec, Lendlease, The Crown Estate, TH Real Estate, Legal and General, Great Portland Estate, and Grosvenor.
Ratcliffe says DfP is currently in advanced discussions with Nabers about bringing the scheme to the UK. ‘They will make the scheme infrastructure and intellectual property available for the UK and, over the next year, we will be adapting their rules, guidance and assurance processes for the UK market.’
The upskilling that will be needed across the sector will require vast industry collaboration, adds Ratcliffe, while industry engagement, training and accreditation to deliver DfP will be a critical next step.
The best buildings in Melbourne are using five or six times less energy than on average in the UK
Design for compliance
The key objective of the pilot studies was to test key elements of the DfP approach, to understand their viability and applicability in UK offices. Cohen says the systemic failings in the current design-for-compliance process were one of the key findings of the recently completed pilots.
‘The current system of applying energy efficiency requirements based on a theoretical model – the results of which are never, and can never be, verified by measurements – is so fundamentally flawed it is remarkable it’s continued for so long,’ he says.
Whole-building assessments started in 2008, after the EU directive on the energy performance of buildings was adopted in 2002, and Part L has been ratcheted up every five years. But Cohen says there is no evidence that buildings – especially those with air conditioning – have been improving their performance in use as a result.
‘The evidence from Australia has brought everybody to their senses because, if they’ve had a total market transformation in the energy intensity of their buildings – which has been measured and verified – why can’t we do that here?’
Most importantly, says Ratcliffe, the way targets are set has to change. ‘We need to stop operating under the false impression that our design standards will deliver outcomes and, instead, specify performance outcomes as part of the brief.’
Advanced simulation
The other key finding, says Cohen, is the power of advanced modelling – now routine in Australia – which is rarely used in the UK because clients do not ask for it, and don’t know why they should.
The moderate climate in the UK has made us complacent, he says. ‘Our buildings are using two to three times more energy than their equivalents in Melbourne. The best buildings in Melbourne are using five or six times less energy than on average in the UK.
‘If we are designing a sophisticated building – which most air conditioned offices are – why not run it virtually in advance of constructing it, and check that it’s going to work?’
Software used in Australia – including IES and EDSL, which, ironically, is made in the UK – is set up to enable this to be done relatively easily. However, the capacity of the model to do that isn’t used in this country, says Cohen, who adds that the model can be used to commission the building and fine-tune it in operation.
The modelling we currently do is all about the fabric of the building, says Cohen, while advanced simulation requires the full detail of the heating, ventilation and air conditioning (HVAC) system – including the ducts, fans, pumps, chillers, boilers – to be entered into the model, and modelling to be done at least hour by hour.
‘On a time-step by time-step basis, you work out: how much heating or cooling is required in each zone of the building; how the HVAC system is going to provide that heating or cooling; how much air will be going down the ducts; what is the pressure drop in those ducts; and what the fan efficiency is, given the pressure drop,’ he says.
“If you allow the market to drive the scheme, it can be very effective in getting the market to compete for higher levels of performance“
‘You have a power curve in your model to describe how efficient your fan is – for example, depending on what load it’s working at – and you work out the amount of energy used for the fan at every time-step, so it gets accumulated to the figure for the whole year.’
As well as getting the model to create the right conditions in the virtual building, the control systems are defined, Cohen adds. This definition can be written into a draft description of operations, which is used by engineers to design the building’s controls. The model can also be used by commissioning agents to check that the real building is being controlled in the same way as its virtual counterpart. ‘You end up with a building that should operate the same as it does in its virtual twin,’ says Cohen.
And it can be done; one of the pilot studies carried out high-quality advanced simulation work on an existing building and the corroborated model represented the real operation of the building. ‘We were able to verify that the model could reflect what was happening in the real building,’ says Cohen.
Reaching goals
As soon as you assign a rating to a building, it changes the conversation, adds Cohen, because you don’t need to be an engineer to understand that – if a five-star building is using three times less energy than a two-star building – it’s a better building.
Setting a minimum standard tends to become a race to the bottom, says Ratcliffe. ‘If you allow the market to drive the scheme by setting its own goals, it can be very effective in getting the market to compete for higher levels of performance – as Australia has proven.’
‘We want people to get confidence and experience with the pioneers projects by testing the water carefully, setting fairly conservative targets without penalties for not achieving those targets, so contractors don’t have to price it into the risk perspective,’ says Cohen.
Nabers has had a long journey to get to the point where disclosure is mandatory, starting off as a voluntary initiative. ‘It achieved market coverage by reducing, gradually, the size of the assets that needed to disclose,’ says Ratcliffe, who hopes the UK will follow a similar trajectory, but in a much shorter timeframe.
‘It’s not just possible – it’s a very exciting prospect,’ says Cohen. ‘The industry will warm to this because it will help M&E engineers attract and keep the best talent, as it’s going to make their job a lot more interesting.’
