Post-occupancy evaluation

Display energy certificates show that a building's energy performance rarely matches the design aspirations. Post-occupancy monitoring and feedback is essential to understand how to improve this.

The Probe studies measured energy performance and user satisfaction. Photo by Bill Bordass.

Monitoring and feedback has long been recognised as a vital part of the building design process but has never been given the prominence or funding needed to make it as effective as it can be. There are three distinct elements:

• review of project performance - covering the brief, design, project management, programming and co-ordination, cost control and build quality
• feedback during one year or more after completion - which helps to fine tune performance in use, inform the client, design and building team and ease transition into full and effective operation
• assessing the complete building and its performance in use, taking account of the users’ perspective.assessing the complete building and its performance in use.

Post-occupancy evaluation (POE) is usually thought of as the third point, although it can include elements of the other two. Although it is self-evident to many that POE should be an essential element of the design process, learning from experience, problem diagnosis, and knowledge management, in reality it has proved difficult to implement.

Among the arguments against are:

• Too costly. Early studies tended to be expensive. Now they are much more affordable but there are still questions about who pays.
• Too risky and threatening. Some are fearful that the results from a post-occupancy study may lead to litigation or added liability. In fact, the opposite is more likely as knowledge and competencies increase.
• Uncertain benefits with property values driven by location, appearance and other features that do not necessarily affect performance in use. What adds value for users is still not valued by the marketplace, although this is now changing.
• It does not easily fit academic disciplines or research criteria, so tends to be sidelined from the mainstream. This is still a problem. For example, only a handful of British schools of architecture feature post-occupancy evaluation in their syllabuses.
• Unclear ‘ownership’ and duty of care. Given that problems are uncovered, who owns what problems? Some prefer to leave well alone.
• Lack of agreement where the public interest lies and lack of co-operation between professions.

However, post-occupancy evaluation has received greater impetus recently, especially from within the architectural profession. The Probe studies showed that it was possible to carry out building evaluation studies that are affordable, and of value to designers, managers, educators and researchers without being too threatening to the design team or occupier. Probe had a relatively simple core ‘portfolio’ approach that benchmarked energy performance and user's attitudes, so that comparable facts were clearly presented. A vital feature was that named buildings were published regularly with a concise statement of lessons learned.

Designers were also given an opportunity to comment on the results. Although funding for Probe finished in 2002, Probe-like studies have been since featured on the Usable Buildings Trust website and the term ‘Probe’ has become a synonym for post-occupancy studies.

One of the conclusions from Probe was that a building’s eventual success was closely connected to monitoring its performance and to fixing problems after occupation. Some of the most successful Probe cases were also ‘green’ buildings. It became increasingly clear that any claims to better sustainability must also be supported by properly conducted evidence on energy, water, thermal comfort and other aspects of occupants’ well being. The intervention of the European Union in requiring energy labels for buildings, itself a by-product of the Probe approach, was also a major factor.

Other approaches to building evaluation including design quality indicators (DQIs) and the British Council for Offices guide to post occupancy evaluation have also been developed. These have joined established methods such as the building use studies occupant survey method and CIBSE’s energy assessment method.

Lessons

Post-occupancy evaluation highlights areas of dysfunction that have the most serious side effects and then aids their diagnosis and correction. For example, thermal discomfort tends to be statistically associated with lower perceived workplace productivity and may also, be a symptom of energy inefficiency through poor fabric airtightness, badly configured control systems, poor management or a combination of all of these. One of the most prominent findings from Probe was that unmanageable complexity was at the heart of poor building performance. Rather surprisingly, this not only applied to larger buildings with complex services but also to many supposedly ‘green’ buildings.

From a sustainability perspective, the best performing buildings were often smaller, less complex and had fewer features that worked better. These buildings were also more responsive to occupants’ perceived needs, especially in how they support everyday work tasks.

The more occupants understand how the building is supposed to work, especially where controls and switches are easy to use, the better. Ease of use must be a consideration when designing sustainable features. Building occupants should be provided with the resources to operate and manage buildings effectively.

Many good design intentions are almost always thwarted by reality, so buildings in use tend to perform less well than buildings in theory. For example, it is commonplace to find buildings using up to three times as much energy as predicted at design stage. Post-occupancy evaluation can help identify where in the process energy efficiency has been reduced. Potential problem areas include commissioning, planning, construction or building control.

There is a need to make rapid changes in the way we design and refurbish buildings and make measureable improvements in their energy performance in practice. We can only do this if we rapidly learn from successes and failures and disseminate that learning across the relevant professions.

Beyond post-occupancy evaluation

Given that results from existing studies like Probe already give clear cues on performance problems, how should buildings be improved? One approach, currently at development stage, is the "soft landings". This is a proposed additional professional service which puts more resources into briefing, pre-handover and long-term operation so that risk is managed more effectively and the building is much more likely to work well from the beginning - a ‘soft landing’.

Work is currently being taken forward by BSRIA in association with the Usable Buildings Trust.

Post-occupancy evaluation gives greater emphasis to performance indicators and monitoring, but it also shows that better sustainability is not just about carbon. For sustainability, thermal efficiency, electrical efficiency, the costs of on-site renewables, imported energy supplies and the carbon content of supplies are just as important, if not more so. The lesson here is to ‘make performance visible’ so that it is more obvious where excessive demand lies. Energy labelling is one aspect of this.

In summary, POE should consider carbon, cost efficiency (whole life), user satisfaction and the impact on other resource domains such as water and waste.

For occupant well being, green buildings have revived interest in the health and productivity benefits of good design. Recent evidence tentatively confirms that green buildings are better from a health and productivity perspective, but probably less so than people might imagine or hope for. It is much harder for designers to resolve the parameters that affect the environmental performance of bigger buildings (by floorplate size and overall height), so lessons from the better performing larger buildings are all the more important. For performance in use, context is all important.

Many contemporary buildings are too complicated, especially with respect to the human and capital resources that are made available to use, manage and maintain them. As Probe concluded, ‘do not procure what you cannot afford to manage’.

Priority: develop a low carbon and renewable energy portfolio
Tags: energy, buildings and spaces