Hidden overdesign in building services: insights from two UK hospital case studies

This paper discusses margins in the context of building services, where the capacity in many buildings, such as hospitals, exceeds the requirements by huge amounts. This oversizing has a direct impact on building efficiency, capital, maintenance and operational costs, as well as environmental and societal impacts throughout its lifecycle. This paper analyses two in-depth case studies of oversized boiler and chiller systems within NHS hospitals, whereby a number of key factors leading to the oversized systems are identified. The excessive and uncoordinated use of margins that are applied during the various stages of building service projects for a variety of reasons, is one significant factor. The lack of requirements information such as energy demand profiles and the use of vague and unreliable data for initial project requirements specifications, is also a major contributing factor. The paper points to the need to develop robust processes that capture the scope and rationale for the margins applied, to communicate project assumptions and stakeholder requirements in a clear and unambiguous format and to develop systems for improved data capture and analysis.