DESIGN MASTERCLASS 10 SYSTEMS ENGINEERING
is the specification of performance targets at each level of integration. Thus, at the highest level, the completed building, we will set targets for the carbon footprint in kgCo2/SQ m, or a similar suitable metric based on occupancy and use. At the lowest level of systems integration we would aim to choose components, such as pump and fan motors, which deliver the maximum energy efficiency. Sometimes these targets are set for us: the Building Regulations stipulate the minimum allowable luminous efficacy for light sources, for example. At intermediate levels of integration we
would set targets, aligned with the overall performance objective, for the output of completed sub-systems. For example, legislation now dictates the maximum specific fan power for a ventilation system or the minimum coefficient of performance for chillers. However, in order to ensure that our overall performance goals are met, we should be setting appropriately aligned performance requirements for all the sub- systems and assemblies. As the components and sub-systems
are assembled to complete the product, the systems engineering methodology calls for testing at each increasing level of integration, referring back to the original component and sub-system specifications. Once again, building services engineers are completely familiar with this process. Components will undergo testing in manufacture as will sub-system assemblies such as air handling units. Sections of the system assembled on site, such as pipe and duct distribution, are all tested to ensure that they comply with the specified performance. Once the systems are assembled, the
building services specification calls for commissioning. During commissioning the systems are operated, tuned and their overall performance is tested. The introduction of mandatory air pressure testing in the building regulations now means that the building fabric is also included in the commissioning process, although not always integrated with commissioning of the mechanical and electrical systems. However, it is still rare that we specify
whole building commissioning or operational testing, an essential step in the systems engineering method,
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and one that is necessary to complete the integration of the building services systems with the fabric and the building operation. When the occupant of a new building is uncomfortably cold and cannot rectify this by turning the heating up any further, then it is likely that the building services engineer will get a call, even if the failing turns out to be one of insulation or draught proofing. It is time, therefore, that the building services profession also took control of the building fabric and operational commissioning, in order to avoid these issues. The final step in the systems engineering
methodology is monitoring, feedback and continuous improvement. This step allows the user of the completed product to refine and optimise its operation for better performance over time. This step also allows the original design decisions to be validated against the final building performance, thus allowing learning from the project to be transferred to the next project to incrementally improve performance. The building services profession has, for many years, been calling for post-occupancy evaluation of buildings and publication of the data in order to permit this cycle of continuous improvement. Building services engineers are already
experienced in many aspects of systems engineering, even if they are not always able to see this approach through to fruition. If we could expand such a systematic engineering approach to encompass the whole building design, including the structure, materials, façade design and internal organisation, then we would have a very powerful tool for designing and delivering replicable and continuously- improving low-carbon performance. When clients and other design team
members are increasingly looking to the building services profession to deliver carbon savings as well as comfort, it becomes essential that we equip ourselves with the tools to manage the contributions of others, as well as the many disparate systems that we are responsible for designing. © Doug King
l Doug King is principal of King Shaw Associates and a visiting professor at Bath University.
The systems engineering approach recognises that complex products such as buildings, aircraft or vehicles require the contributions of many engineering disciplines to work in harmony
January 2012 CIBSE Journal 49
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