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Can we make zero carbon in use a reality?

Judit Kimpian

Despite umpteen regulations and rulings, the performance gap on sustainable buildings remains too large. Is there a solution?

One of AHR's cross-laminated solid timber staircases under construction.
One of AHR's cross-laminated solid timber staircases under construction.

In recent years we have seen a plethora of legislation and incentives to improve the energy performance of buildings and it is hardly surprising that built environment professionals can find it challenging just to keep track of compliance requirements. Are these regulations achieving the expected reductions in energy use – and what is the cost? 

We’ve had changes in Building Regulations; the Green Deal; boiler replacement schemes; the CRC Energy Efficiency scheme; the Renewable Heat Incentive; Enhanced Capital Allowances, and Feed-In Tariffs and more. How effective have they been? Are the 2020 ‘nearly zero’ targets for new buildings realistic, and how do built environment professionals feel about them? 

A fundamental feature of current legislation is the lack of a feedback mechanism at both building and stock level. Determining the impact of legislation on building performance is not straightforward and is the subject of several PhD and post-doctoral research studies. Early results are not encouraging. 

Evidence based

Recent studies, such as Innovate UK’s Building Performance Evaluation (BPE) programme and UCL research into the impact of large-scale fabric and boiler improvements in housing, have gathered important evidence about lower than expected performance improvements in use from typical efficiency measures. The BPE programme offers insights into excessive costs and potential productivity losses associated with the performance gap that dwarfs the cost of excessive energy bills.

Using crowd-sourced data, the RIBA/CIBSE CarbonBuzz platform has demonstrated a 1.5-2-fold difference between calculated and achieved energy use in the education and office sectors. This is worrying enough for the RIBA Sustainable Futures Group and Architects’ Council of Europe to make the ‘building performance gap’ a key priority. The European Commission is also looking to study further how low impact buildings, certified according to existing schemes, perform in reality.  


What’s missing is embedding feedback from completed buildings – the disclosure of predictions as well as performance in use

Legislative drivers and change 

Finding ways to achieve drastic improvements in building performance is imperative. In 2008 the UK government signed up to a legally binding target of an 80% reduction in CO2 emissions by 2050 compared to 1990 levels (34% by 2020). Its 2011 Carbon Plan aims to reduce emissions from all UK buildings to ‘close to zero’ by 2050 – a reduction of 24-39% from 2009 levels by 2027. 

The EU Energy Performance of Buildings Directive (EPBD) and Energy Efficiency Dir­ective (EED) have been updated, requiring the EU to implement a 40% reduction in emissions below 1990 levels by 2030 and for nation states to increase energy efficiency by at least 27%.

Buildings account for around 45% of our total annual emissions, with 25% of these coming from homes. Energy efficiency improvements in buildings offer the most promising area for regaining growth in the construction sector. 

But achieving these goals is a challenge. The EPBD requires Energy Performance (EPC) Certificates for all buildings. From 2018 none with a rating below E can be let and there are indications that this is a major driver for landlords. However, growing scepticism surrounds the relationship of EPCs to actual performance. The cost of improving on an EPC rating is relatively low but several recent studies have found no relationship between EPCs and operational energy use (JLL, TSB BPE, etc.).

The 2010 recast of the EPBD requires member states to ensure that after 31 December 2018 all new buildings occupied and owned by public authorities are nearly-zero energy buildings (nZEB), a demand covering all new buildings by 31 December 2020 . The definition of ‘nearly zero’ is up to member states and in the UK the debate around what constitutes a nZEB has been led by the Zero Carbon Hub for housing and the UKGBC for non-domestic buildings. 

The UK government has committed to meeting nZEB targets for new housing by 2016 and for non-domestic buildings by 2019. Yet there is still no final conclusion on what the ‘minimum on-site carbon emissions threshold’ might be, or on the definition of allowable solutions which permit remaining emissions to be ‘tackled through nearby or remote measures’. 

As countries like Belgium mandate all new buildings to comply with the highly credible PassivHaus standard, British lawmakers appear to be lowering standards. The right legislative framework is essential to improve building performance – and building regulations have repeatedly been shown to be the most effective way to deliver a step change in construction practice. What’s missing is embedding feedback from completed buildings – the disclosure of predictions as well as performance in use.

AHR’s Bath and North East Somerset’s offices in Keynsham nearing completion.
AHR’s Bath and North East Somerset’s offices in Keynsham nearing completion.

A way forward

Seven detailed studies undertaken by AHR as part of Innovate UK’s BPE programme have highlighted the unintended consequences of the existing EPBD-driven building regulations compliance process. As Part L only requires the performance evaluation of a building under standardised conditions, risk factors relating to construction and building operation cannot be considered and addressed at design stage, nor will solutions be incorporated into contracts and specifications. Likewise, a compliance calculation cannot act as a basis for comparing design stage predictions with actual performance as a full energy use forecast is required to diagnose any problems post-completion.     

Having studied the consequences, BPE participants have started to build on the lessons learned. AHR’s freshly completed design for the Bath and North East Somerset council offices and civic centre targetted operational energy use from the outset. Gaining the Display Energy Certificate (DEC) A rating was part of the client’s brief, and the team came up with a novel approach. A building ‘energy budget’ was developed early on, accompanied by a risk register listing every aspect of the design that contributed to the energy rating. Updated at key RIBA Plan of Work stages, the energy budget and the risk register were incorporated in the contractor’s prelims. The contractor (Willmott Dixon) in turn signed up to the delivery of the DEC A rating along with the requirement to measure and benchmark the building’s energy use on a monthly basis, following handover, during the first year of the building’s operation. 

This not only delivered innovative architecture but helped eliminate many of the usual problems that arise from the value engineering of critical elements or poor commissioning. Building features relating to the long-term resilience of the building were retained, such as passive ventilation, floor-to-floor heights, vent voids, thermal mass, window specification, etc. Significantly, the project team agreed that as  the design exceeded BREEAM energy-related criteria, that certification was not needed. The process set out by the team facilitated collaborative working to share all energy-related data and to recover situations that may in different circumstances have led to adversarial action.

If the project performs to expectations after year one, it will exceed building regulation requirements and operate over and above nZEB targets. It would also demonstrate that setting the right KPIs and opting for measurement, verification and disclosure could achieve better than nZEB performance in use and significantly reduce regulatory burden.

Next steps

With EU member states actively seeking a lighter legislative touch, this project has attracted the attention of organisations such as the Architects’ Council of Europe, the European Commission and UK government departments. 

To satisfy Article 11(9) of the EPBD recast, significant EU effort has developed a voluntary common certification scheme for energy performance of non-residential buildings. This would harmonise the rating system across member states and align the reporting of as-designed and in use performance. 

If it is successful, it may be possible to supplant this approach to the reporting of resource consumption in buildings too. At a recent Construction 2020 workshop the benefits of mandating disclosure as opposed to detailed regulations were discussed constructively. Given the simplicity of the scheme and the appetite for big business to adopt it, the regulatory framework might just be subverted. •

Dr Judit Kimpian is director of sustainable architecture and research at AHR, chair of the Architects’ Council of Europe sustainability group, and leads CarbonBuzz



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