The reality gap in buildings' operational performance
The new Building Performance Evaluation review from Innovate UK reveals how low-carbon buildings are still falling dramatically short on their energy-efficiency promises. Elaine Knutt asks how the industry can address the problem.
Anyone tackling the 110-page report of the £8m Building Performance Evaluation review is likely to experience a worrying sense of deja vu. It’s a summary of independently assessed post-occupancy evaluations and reports on more than 100 low-carbon buildings completed in 2008-11, comprising 59 residential projects and 48 in the non-domestic sector.
It forms a compendium of all the cumulative failures in design, construction, commissioning and hand-over that together add up to a yawning “performance gap” between design intent and operational energy.
But for most readers of Construction Manager the narrative of the BPE reports will prove all too familiar. Heard the one about the rooftop ventilation systems not commissioned properly? Or the biomass boilers installed to get a better EPC or BREEAM rating, but then never switched on? Unfortunately, you probably have – from a major study by Leeds Beckett University in 2012, from an earlier series of studies by the Carbon Trust, or even from CIBSE’s Probe studies from 1995.
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The conclusions of the Innovate-UK funded BPE study, in the words of one monitor, are “eyebrow raising”. It revealed performance gaps of two, three or five times the amount of energy foreseen at design stage, with almost all buildings failing to deliver what they were designed to. Two-thirds of the buildings included onsite renewable energy generation to reduce their energy requirements – but two-thirds of this group experienced problems that reduced their energy savings.
The performance of low-carbon housing seemed particularly concerning. Measured energy use in the “low energy” homes – that is, for electricity and heating fuel alone, excluding “unregulated” energy for appliances – differed by a factor of nearly 10 between the lowest and highest. In the social housing sector, the air-tightness of 46% of the homes in the study was below the design intent, and nine of 28 of the assessed schemes in fact failed to meet Part L.
So how should the industry react to the BPE catalogue of culpability? For some commentators, the scale and consistency of the findings should be a wake-up call for an industry happy to “sell” clients the promise of an energy-efficient product, then failing to deliver.
Domestic troubles: The Innovate UK report looked at 76 home types across 52 residential projects. While Passivhaus properties performed well, and average air-tightness was good, regulated energy use varied by up to a factor of 10 between the best and worst performers.
Building Data Exchange: This web portal, launched in conjunction with the Digital Catapult project, invites the industry to collaborate on new data-driven approaches on reducing the perfromance gap. The initiative was kicked off with a hackathon event in February.