Overdesign in building services: The hidden energy use

This paper categorises and describes the various types of margins that are applied during building services design, and highlights the various stakeholders involved, from the early specification of requirements, through to the engineering design specification and installation. Using a case study of a hospital boiler upgrade, the paper differentiates between margins built into the to regulatory, clinical, and contractual requirements, and the margins applied through the engineering design choices that allow for various contingencies and uncertainties. To meet energy targets, hospitals invest in products that use less energy. Whilst such interventions, such as lighting upgrades and control improvements provide some efficiencies, over-design of core systems often negate the savings. The over-specification and over-design of building service systems often results from the cumulative addition of various design margins. It is quite possible that sometimes margins are added as a matter of habit with no real thought as to whether they are really applicable to a particular situation, calling into question the issue of design procedures.