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Immediate (Integrated Management of Margins through Evaluation, DesIgn, Analysis, Tracking and nEgotiation)


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Authors

Eckert, Claudia 

Abstract

Over-engineering is a hidden source of inefficiency in building service systems and can add significantly to their design, installation and running costs. Over-engineering also reduces the sustainability of systems, increasing maintenance and replacement costs and whole life CO2 emissions. One cause of over-engineering stems from the cumulative effect of margins (error, safety etc.) added to the specification by multiple stakeholders, to mitigate against their own particular risks. The project carried out a case study of a replacement energy system at the Oxford John Redcliff hospital, a recent PFI project.

Although the new system makes considerable savings compared with the previous failing system, the system size appeared disproportionate. Individual stakeholders agreed that the new system was overdesigned, but could not quantify or cost the overdesign. Most were unaware of the rationale behind the original high specification system, so that margins accumulated and could not be challenged. The case study illustrated how a rational decision at the time, lead to an oversized solution.

The project analysed the causes of the overdesign relating to procurement and specification and developed insights that can inform the decision making and management of building service projects. It also developed recommendations for designing flexible building services with suitable margins.

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CDBB

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