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Energy rating — it’s not as easy as ABC Comment Roderic Bunn

The gap between buildings’ energy ratings at design stage and what they actually achieve is often huge — with potentially dire consequences for the green agenda.

THERE’S A NEW phrase doing the rounds. It’s a murmur at the moment, nowhere near a cacophony, but the voices are growing. We are, they say, entering into “a perfect storm” over the accreditation we give our sustainable buildings. It starts with the EU’s Energy

Performance of Buildings Directive. Among other things, this Directive required member states to enact energy performance certification. This led to Energy Performance Certificates (EPCs) in Part L of the Building Regulations. Certificates sprung up in reception areas up and down the land proclaiming new public sector buildings to be variously A or B rated. Sometimes C, but never lower. The “bad” news was that any building with an EPC also had to show a Display Energy Certificate (the DEC) a year or so after completion, showing the building’s actual energy use. Invariably, the DEC rating has a very different tale to tell: an A-rated building at design became a C at best, and often D or below. It is not unusual to find schools with a B-rated EPC but an F-rated DEC (see table below of random school buildings). It doesn’t matter that EPCs and DECs

measure different things (the EPC doesn’t include plug-in electrical loads, for example), because the damage has been done. Public sector clients were led to believe their buildings were sustainable and low energy in practice — a belief bolstered by BREEAM scores of Very Good or Excellent — only to find the reality was rather different. The upshot is that clients have begun

to think EPCs aren’t worth the paper they’re written on and are now asking for A-rated DEC buildings. How long before this becomes a contractual requirement, one wonders, with penalties for non- achievement? And will professional indemnity be a good enough umbrella? Doubts are also creeping in about

the real meaning of the BREEAM rating. All that cost, time and effort to get a green rating and some renewables, and for what? Small wonder that the Coalition’s storm trooper at the education department is the one to snap vicious. At


the time of writing, Michael Gove wanted to ditch BREEAM for schools. Are we seeing the start of its demise? What’s clear is that we need to get new

and refurbished buildings to perform far closer to their design intentions and close the loop between what we think is going to happen and what actually happens. This is the intention of the Soft Landings process. Soft Landings is a free- to-use process for a graduated handover of a new or refurbished building, where a period of professional aftercare by the project team is a client requirement, and planned for and carried out from project inception onwards and for up to three years post-completion. Government departments are to begin trials of the process as part of the recently announced procurement shake up. Soft Landings requires the team to

focus beyond regulatory compliance, to finish things off properly and follow through with professional aftercare to get the building to perform properly. Research published last year by the Carbon Trust revealed that despite technical design support and funding for renewables, the study buildings performed nowhere near design predictions. Commissioning — especially of complex renewables systems and building controls — was usually rushed, incomplete and badly recorded. Detailing and finishing was poor. Follow-through by the project team to troubleshoot and fine-tune was cursory at best. Energy consumption was sometimes three times the design prediction — in the worst case it was a factor of five. Designers may argue that what you

Bessemer Grange

Occupied Sep 2010

Sep 2010

TFA m2 685

call a design prediction is actually just a modelled calculation to achieve Part L compliance, it doesn’t count everything. In any case, they say, things change. This is true. But design calculations have a nasty habit of being communicated as predictions, and predictions have an equally nasty habit of becoming someone’s published target. So what is the point of Part L energy targets if they don’t reflect reality, and they are overtaken by events? The gap between what we think is going to happen, what we model and base compliance on, and what actually happens, is getting wider. This performance gap needs to be closed. The trigger for seriously tackling this

performance could well be the building insurers and the lawyers. Developers that have invested in low-energy features, renewables, and environmental performance ratings of Excellent, may find that the rateable value of their property — the market perception — is not what they were led to expect. And if they can’t get a return on their investment through rental, be in no doubt, they will make someone pay. Woe betide the professional who said an environmental rating would improve a development’s rental value. If you want to avoid this perfect storm,

you need Soft Landings. Either the industry voluntarily takes greater custody of building performance in-use, or it will be forced to do it. Either way, there’s no real alternative. Roderic Bunn runs the Soft Landings initiative at BSRIA. For more information contact

Gap year: The difference between academy energy EPC ratings and DEC performance Project

Loxford School of Science and Technology Apr 2010 Brine Leas (Sixth form centre) Stockport Academy Petchey Academy

Pennywell Academy 360 Cressex Community School

St Peter the Apostle High School

14,610 2030 Excellent 2799 300

Sep2008 10,490 900 Sep 2007 Jun 2009 Jul 2010 Jun 2009

10,490 1200 10,172 860*

B (31)

Very good B (36) Very Good B (47)

11,624 500**** Very good B (31) 16,185 1600

**Error on floor area calculation


N/A E (106)

Very good C (64) *** G (200) Very good B (34)

Very good B (25) ***** N/A ***Error on fuel source

D (96) ** N/A

E (116) E (est) E (est) G (est) F (146) N/A N/A

TFA: Net floor area EPC: Energy Performance Certificate DEC: Display Energy Certificate BER: Building Emission Rate in KgCO2/m2 per annum OR: Operational Rating in KgCO2/m2 per annum *Design figure. Current occupancy 1100+

****Currently under occupied full capacity is 1100 pupils *****Scottish EPC which uses a different methodology

Pupils BREEAM EPC/BER DEC/OR 2010 DEC/OR 2011 Very good

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