Design Fine Tuning?


Julia Evans, BSRIA Chief Executive

Julia Evans, BSRIA Chief Executive

BSRIA has been involved in many recent projects including an independent assessment of the realised performance of low energy / environmentally conscious buildings.  This includes projects associated with the Technology Strategy Board’s Building Performance Evaluation (BPE) programme.

The emerging results for more than 50 non-domestic buildings have now been analysed by BSRIA to look at what works well, and when things don’t, why this is the case.  It’s always difficult to generalise based on such a diverse building stock, ownership profile, procurement route, supply chain capabilities, and operational approach, but its clear that in many of the buildings there is a significant performance gap between design intent, and realised performance.  Analysis of such data is always a challenge.  How does one attribute, for instance, any shortfall in performance between the specification, design, construction, commissioning process, and to operational issues such as sub-optimal energy management and / or changes in operating regime such as an extension in occupancy hours.

However one lesson inferred from the analysis is that with some low carbon (and / or energy) buildings one of the unintended consequences is that sometimes the building has been finely “tuned” to minimise carbon (and / or energy), and capital costs at the expense of the building’s resilience in the face of, say, changing patterns of use or internal gains.  Put simply, if a building has been engineered to reduce energy and or carbon for a particular set of operating conditions, and one way of achieving this is to simply size ventilation, and air conditioning plant in line with those conditions, what happens if say internal gains increase as a result of higher occupancy loading?  In practice it is found that some environmental designs lack the flexibility to cope with changes in business use because of limitations built into their design.  This happens with more conventional buildings, with the difference for environmental buildings being more pronounced because the design in many cases is more finely “tuned” as we move ever closer to “near zero”, or “very low” energy / carbon buildings.

BSRIA’s experience identifies many of the good practices required to ensure environmental buildings work well, and also the impact of poor practice.  Overly sensitive design is one cause of poor performance in practice.  So the question is why do some clients and their design team include a sensitivity analysis to design services and size plant so as to ensure resilience, whereas others adopt an approach best characterised by “lowest capital, highest environmental ranking, never mind about actual performance in use”?  The likely answers are complex.  Those found by others like Latham and Egan come to mind for some instances: informed clients recruit supply chains who know their business, and both understand implications of design decisions; post-occupancy-evaluationanother is the chasm which can often occur between those who specify, procure, and lease buildings, and those who occupy and manage them.  Perhaps a third is that once a building has been occupied, too seldom is thought given to how the building will actually work in the face of changes in occupant requirements.

The question for BSRIA is how we can provide a steer and guidance to our members and the industry as to how best to ensure that we build the next generation of environmentally sensitive buildings to be even more resilient in the face of likely changes those buildings will face over their lifetime.  A building which has a very low carbon and / or energy design use, but which fails to provide a productive environment in the face of foreseeable changes in operating conditions can’t really be described as “sustainable”.

This blog was written by BSRIA’s Chief Executive, Julia Evans. For more information about BPE you can visit our website or visit the TSB’s BPE pages where you can look at case studies and methods of BPE (you may need to register to access these). 

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