CAN BUILDING DESIGN learn from its own successes and mistakes? How do you measure the success of a design if not by looking at the well-being and health of the users? And how can you find out whether the indoor climate really does enhance people’s well-being?
The idea that the systematic evaluation of existing buildings could generate knowledge that will be useful when designing new ones is not new. A method, first deployed in the USA and Great Britain, was developed in the 1960s and 1970s that consisted of scrutinising existing buildings and asking the users about their experiences with the building. It is known by the collective English term ‘post-occupancy evaluation’ (POE).1 The first user surveys were carried out towards the end of the sixties in student halls of residence in America. In the seventies, the method was expanded to include hospitals, office buildings, schools, social housing, and military facilities. Since the 1990s, post-occupancy evaluation has become a more common procedure, particularly for offices and administrative buildings. There are two main reasons for this: on the one hand, it was recognised that the buildings often consumed far more energy than previously calculated; on the other, the numbers of complaints about the poor indoor climate and malfunctioning technical equipment began to escalate. Investigations in the USA and in Germany have shown that the average user satisfaction in energy-efficient or LEED certified office buildings is no higher than that reported for most office buildings.2 Experts put the blame for the performance gap between theory and practice primarily on the buildings’ increasingly complex technical equipment and the inadequate induction given to subsequent facilities managers and users during the handover.
Meanwhile, in some countries the legislators began to react. In the UK, for example, all new-build public buildings since 2016 are subjected to a three-year monitoring process that includes an annual user survey.3 But the situation for residential buildings is quite different – and not just in the UK. There are only a few systematic studies of people’s well-being at home. According to Fionn Stevenson, professor at the School of Architecture of the University of Sheffield, the rarity of post-occupancy evaluation in this sector is linked to residents’ expectations of privacy: “Simply gaining access to people’s homes, which are private by their nature, can present a real barrier.” One aspect that may play a role in this could be the fact that the clients of office buildings have a vested interest in a healthy and productive workforce, while the owners of residential buildings do not benefit directly from the improved well-being of their tenants. Nevertheless, there are a few hopeful developments, which will be discussed below.
Measurements and surveys: the methods of post-occupancy evaluation
In principle, post-occupancy evaluations can be carried out at any time during the lifecycle of a building to provide key insights: hindsight is useful as it allows the planning process and its success to be analysed; current insights can be used to adapt the building to the needs of users, while foresight can be used to learn about planning similar buildings in the future.
According to Fionn Stevenson, a POE offers numerous benefits: it reduces lifecycle costs and the environmental impact of buildings, decreases the developer’s liability risks, minimises the expenditure required for maintenance, increases user satisfaction, and generates valuable knowledge that can be incorporated into making future designs better. A post-occupancy evaluation usually includes the following steps:
“People are the best measuring instruments. They are just harder
- a tour of the building together with the users and/or the facility manager
- technical measurements (e.g. room temperature, heating energy consumption, light/level of illumination, amount of CO2 in rooms, air humidity, ...)
- user surveys using printed or digital questionnaires, or – more rarely structured interviews
Technical measurements can, in themselves, provide interesting information about user behaviour in residential buildings. It is well known, for example that heating energy consumption in buildings that are otherwise identical in terms of construction can vary by a factor of three or even more, depending on user behaviour. In nine recently renovated apartment buildings in Karlsruhe, researchers from RWTH Aachen attempted to uncover the possible causes for this.4 To do so, they measured room temperatures based on thermostat settings but also determined ventilation behaviour using window contacts. They found that almost all combinations of temperatures considered agreeable by tenants and fresh air requirements were present. Some tenants preferred room temperatures of 24°C but kept their windows open 24 hours a day even in winter, while other tenants were content with an ambient temperature of 19°C and almost never aired their rooms.
But in order to get to the bottom of the motives for such behaviour and find out whether residents actually feel comfortable in the indoor climate they have chosen for themselves, one has to talk to them. Only a combination of measured physical data and qualitative statements by residents will reveal what the British building evaluation specialist Bill Bordass calls “the story behind the data”. Together with Fionn Stevenson and Adrian Leaman, he wrote in an article published in 2010: “In our experience, nothing betters case studies of named buildings backed by thorough data collection, benchmarked against a national sample finishing with a list of lessons learned, preferably including reflections on the results by the parties directly involved, and especially the design team.” 5
What do we want to know?
Questionnaires and their contents
Numerous questionnaires – some of them standardised – have been developed in the last 30 years as a means of surveying the users of buildings (Fig. 5). The questionnaires most commonly used internationally are the British Building Use Studies (BUS) Questionnaire6 and the CBE Occupant Indoor Environmental Quality Survey developed at University of California, Berkeley7. Both were originally developed for office buildings, schools, and other non-residential buildings; since 2010, the BUS questionnaire has also become available in a version for residential buildings. The questionnaire has also been deployed when carrying out user surveys for the certification systems NABERS (Australia) and BEES (New Zealand). The international engineering consultancy Arup now curates the commercial version of the BUS questionnaire. Adrian Leaman of BUS estimates that around 60% of all surveys that use the BUS option are carried out by planning offices and 40% by university institutes. When the questionnaire was developed, he says, care was taken to keep it as short as possible and to focus on aspects that designers and managers can actually influence. Leaman believes it is important that the questionnaire is both practical and viable because, when they survey users, planners and academics are often pursuing very different and, in many cases, incompatible goals: “POE in the university sector has another agenda. It is often far too statistical and/or modelling orientated. And the work does not