Post Occupancy Evaluation for Low energy buildings

If we claim that our buildings are green, ecologi­cal, sustainable, carbon neutral, or energy efficient, we need to ensure that we know how well they perform once they are in use, and how closely this relates to our design intentions. There continues to be a discrepancy between design input and outcome in the construction industry as a whole. Examples of buildings that have been monitored green or not, show that, normally, the results are not as good as the design expectations (Ni Riain et al, 2000; PROBE team, 1995-2002). Knowing what caused the problems and why can be a positive thing, if you learn and share your findings with others. The aim is to create virtuous circles of continuous improvement (Bordass et al 2001).

Buildings are active systems, with users and owners in constant interaction. Occupants just use the building features to suit their needs and their behaviour may not accord with the design intentions. We have to decide what we would like to know about our buildings in use and find out the best way of obtaining that information.

Collecting feedback

As part of a partners in innovation project, the Usable Buildings Trust (UBT) collected available feedback techniques into a multi-dimensional matrix. The matrix can be viewed by sector, the stage of development of the technique (e.g. is it new or well-established), and where to use in the life cycle of a building or a construction project'. The portfolio was expanded from ten general-purpose techniques, to include a number which are specific to a particular sector (e.g. schools).

Feedback collection techniques

Techniques currently fall into six main groups, as outlined below:

Facilitated discussions: where team members discuss and share their experiences in a positive non confrontational manner.

Packages of techniques: where more than one technique is used as a set to provide an all around POE assessment. PROBE (post-occupancy review of buildings and their engineering), for instance, includes a preliminary questionnaire, a building use studies' occupant survey, CIBSE TM23 energy assessment and reporting methodology, and sometimes, a building envelope pressure test to CIBSE TM23. This combination of soft and hard issues was used for the PROBE studies series, published in the Building Services Journal between 1995 and 2002.

Process improvement: where special arrangements improve the design and construction process, in particular to learn more from existing buildings and the experiences of the client, project and management teams, to facilitate a smooth transition between handover and occupation, and to improve performance in use.

Questionnaires and interviews: these include paper and web administered questionnaires, and one to one interviews. For example, the building use studies (BUS) occupant survey and bench marking method covers 44 variables, including a self-assessment of health and productivity. Design Quality Indicators (DQI) has 100 questions organised on three sections: functionality, build quality and impact.

 

Technical assessments: these methods help define how well design requirements match achieved outcomes with regards function and performance. For instance, medical architecture research unit (MARU) evaluation studies’ provides a range of techniques for health build­ings.

Sustainability: these techniques look at the impact of the buildings in their surroundings. Of these, BREEAM stands amongst the best known in the UK, but at present it is mostly design-focused and provides an overall rating with little information on specific achievements. CIBSE TM22 focuses on energy use; it can be used to report design expectations, actual energy use and predicted savings from changes

Type of buildings: The PROBE portfolio includes techniques suitable for defence, education, health, office, leisure, housing and other buildings. Some other techniques such as BREEAM, BUS occupant survey, CIBSE TM22 and 'learning from experience' are suitable for most building types. Others, like AMA Toolkit (offices and similar workspaces), NEAT (health), MARU (health), DEEP (defence), are suitable for specific building types.

A user group of designers and clients tested some of these techniques on case studies of their choice, in the course of a UK research project that ran between 2001 and 2004 (Bordass, Leaman, 2005).

What to test for?

We are getting used to claims that buildings (or whole developments) are green, energy efficient, or even carbon neutral. Those claims need to be substantiated by some independ­ent assessment in-order to prove their success. POE has shown that expectations tend to be more optimistic than the results.

There are often valid reasons for some of the differences, but they need to be understood if we are to produce better designs in the future, which take proper account of what really happens. As a minimum we suggest that you aim to go back and check two things.

1.        Natural resource use (energy and water)

Energy use, where it is not provided by renew­able sources, is the main source of CO2 emissions. We suggest you collect data on a monthly basis and analyse usage on a yearly basis, keeping electricity separate from other fuels. Translate energy use into CO2 emissions.

Benchmark your emissions against similar buildings, if data exists, or collect your own to compare your year on year progress. If you use renewable sources of energy, measure their contribution and establish how much you are reducing emissions. You can analyse the data further to know which uses are the greatest (e.g. lighting, office equipment, catering...)

More data on truly green buildings should encourage improvements beyond the current good practice standards, which sadly are often not reached. Useful techniques available include:

  • National Energy Foundation CO2 calculator
  • CIBSE TM22 energy assessment and reporting methodology.

Water is, increasingly, a scarce resource. Meter and monitor your water use, analyse what it is used for, and communicate results. Benchmark your water use against similar build­ings. Useful techniques available include the Envirowise water account tool"

2.       Occupant satisfaction

To be successful, 'green' buildings must provide a comfortable environment for occupants. Sadly, this is not always so. Designers normally do not occupy the buildings they design, their clients or tenants do! The challenge is to make buildings easy to operate and live with, not over complicated, with effective controls (that give feedback of what they do!), and have sensible default conditions, which provide safe condi­tions with minimum energy use.

Occupant satisfaction is often considered a 'soft' issue, supposedly difficult to measure and quantify. However, there are well-established ways of recording and evaluating occupants' opinions and needs, such as questionnaire surveys, formal discussion groups and accom­panied building visits and interviews.

As a minimum, return to the building once it has been occupied for a while, after all the initial tuning faults have been resolved, and have a frank discussion with the users. Match your methods to the building type - a bulky questionnaire might not be appropriate for a single dwelling. Record the responses to provide a reference if you decide to go back further down the line. Ideally, share your findings so that others may benefit from the lessons learnt.

Important questions are:

  • are basic needs, like space and comfort
  • requirements, being properly met?
  • do people feel healthy?
  • does the building affect productivity?
  • what are the good features?
  • what are the annoying features?
  • what can be improved tomorrow?

Useful techniques available include the Building Use Studies (BUS) occupant survey (widely used in the UK and internationally, with benchmarks available).

Conclusion

POE studies provide lessons that we can learn from - some general, some specific. For major effect, those lessons from case studies need to be communicated to a wide audience. Public exposure of green buildings will help promote their features, intelligent critiques will facilitate their acceptance and greater realism about their intended and achieved performance will improve future implementations.