Integrating occupant preference and life cycle energy evaluation: A simplified method

Building energy evaluation and assessment methods have evolved over the last decades towards sophisticated tools, which can support designers in minimizing building energy use. However, the majority of building energy performance evaluation methods and tools generally do not include a life cycle perspective, choosing to ignore the use of resources associated with the additional materials and systems employed to reduce the energy use of buildings in operation. Considerations of 'acceptable' or 'expected' levels of comfort or occupant preferences are also frequently ignored outside the research community. This paper describes a simple methodology which integrates life cycle energy analysis and comfort expectations with building energy evaluation. It discusses the potential contribution of the occupants' preferences not only in the energy use of buildings in operation, but also the embodied energy associated with equipment and systems. The method is demonstrated in a case study considering a house in a maritime climate with the options of either mechanical or natural ventilation, and some differences in thermal and ventilation preferences. In the study it is observed that as 'zero heating' demand is approached, the embodied energy of materials and systems becomes significant. The differences in occupants' expected temperature and ventilation levels can be important issues to consider when selecting heating and ventilation systems for minimum life cycle energy use.