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Post-occupancy evaluation (POE) is the general term for a broad range of activities aimed at understanding how buildings perform once they are built. It tries to answer four broad questions: 'How is this building working?', 'How can it be improved?', 'Is it intended?', 'How can future building be improved?' (Preiser & Vischer, 2005, p.72). It is becoming increasingly difficult to determine if buildings are functioning according to their designed function because in today's competitive market, 'organisations have complex and rapidly evolving needs; new and untried building materials and construction technologies are used; services designs increase in variety on a daily basis; occupants have discovered 'green', lifestyle and health agendas; businesses and governments are increasingly cost conscious' (Eley, 2001, p.165). A post-occupancy evaluation differs to that of other building evaluations such as ones that appraise the materials, engineering, or the construction of a facility. Examples of these evaluations include testing of structural components, geotechnical surveys, mechanical systems performance checks or life-cycle analysis and costing techniques. (Preiser, 2002). A POE focuses more on the functionality of the building in relation to the people and the organization using the facility. 'The purpose of POEs is to enable building operators, managers and occupants to provide feedback on performance aspects of the building and other factors that affect their working or living environment' (Canada Green Building Council, 2010). As a result of the feedback acquired from the POE the design team can take advantage of the information received from the results of the POE and incorporate it into future design schemes since the significance of conducting POEs considerably 'reduce the uncertainty in making design decisions' (Rabinowitz, 1988). This will aid in developing structures which are not only more cost effective, but also identify inefficiencies within previous designs, share data obtained from previous developments and in addition add increased functionality and comfort to the occupants of the building.
History of POE
POE in the UK
While building evaluations are not new, POE as its known emerged around the 1960's. The Royal Institute of British Architects (RIBA) in 1963 published a document outlining a standard method of operations used in the construction of buildings called the RIBA Plan of Work. 'It represents a logical sequence of events that should ensure that sound and timely decisions are made during the construction process. The model will only need slight adjustments depending upon the size and complexity of the project' (Nelson et al., 1999). The project progresses from inception to feedback, i.e. from stages A to M (figure 1) in a linear fashion requiring the completion of one stage before proceeding to the next. (Nelson et al., 1999).
Figure 1 illustrates the five main categories which make up the RIBA Plan of Work theory, namely: Pre-design, Design, Preparing to build, Construction and Post-construction. The final stage, stage M is when the Architects would examine the success of what they had done. This stage could be considered the prelude to Post-occupancy evaluation within the built environment.
Figure 1 - Diagram of RIBA Plan of Work, (Nelson et al., 1999, p.230)
'Ironically, the year this book was published, the RIBA removed Stage M from its publication, reportedly because clients were not prepared to pay for feedback as an additional service, and the RIBA did not wish to create the impression that feedback would be undertaken as a matter of course. Today the wheel seems to have turned full circle, with the RIBA (1999) saying that "the biggest improvement to be made (in customer focus) is in systemizing feedback and in instituting post-occupancy evaluation". In 2003, forty years after Stage M first appeared, the RIBA Practise Committee decided to reintroduce it into its published documents' (Preiser & Vischer, 2005).
POE in the US
POE was around during the 1960's although it became more popular during the 1970's when it was used in military facilities, mirroring their post-operational review debriefings (Preiser & Vischer, 2005). Elsewhere seminal work by Sim van der Rijn on the initially poor performance of student dorms at the University of California, Berkeley. It was not called POE, but an early systematic approach at assessing performance from the user point of view. (Bordass & Leaman, 2009). Soon after the Environmental Design Research Association (EDRA) was setup which aided in sustaining the practise of POEs in North America, principally in the academic mould and concentrating on psychological aspects of user satisfaction.
Benefits of POE
'The sad fact is that hardly any architecture or engineering firms consistently collect information on whether or not their buildings work, and none make the information available to others,' wrote the authors of the Probe Studies, a series of building performance evaluations commissioned by the Building Services Journal in the U.K. and completed in 1999. 'All this despite clear evidence that managed feedback produces better buildings.' (Malin & Jessica Boehland, 2007)
A POE aids in identifying whether a building functions as the architect and owner intended it to during the design stage. It has additional benefits for architects such as strengthening the client-architect relationship; validating life-cycle performance projections; and enhancing knowledge for future designs of a similar nature. Zimmerman & Martin (2001) note that 'The over-arching benefit from conducting a POE is the provision of valuable information to support the goal of continuous improvement'. POEs are particularly valuable in evaluating new technologies including innovations in resource conservation, natural ventilation, use of daylight and photovoltaics. (Malin & Jessica Boehland, 2007)
Other benefits POE include;
Rapid feedback leads to quicker reaction (rather than other research routes)
Is closely linked to design and therefore can become actionable easily
Improves the ability to predict and therefore minimises risk in the future
Good results can be effectively marketed
Decisions can be made quicker if relevant evidence is available
The alternative is to continue to build in ignorance of the outcomes (Kolokotroni, 2009)
POEs are an important tool in planning the refurbishment of existing buildings. It helps clarify perceived strengths and weaknesses in order to focus resources where they are needed. It identifies where building design adjustments are necessary to support changing practices, markets, legislation and social trends. (Watson, 2003)
Preiser, Rabinowitz and White (1988) state that depending on the objectives of the client organisation and the time frame involved, POEs have uses and benefits over the short, medium, and long term (table 1).
Table 1: Benefits of POE over the Short, Medium, and Long Term
Identification of and solutions to problems in facilities
Proactive facility management responsive to building user values
Improved space utilisation and feedback on building performance
Improved attitude of building occupants through active involvement in the evaluation process
Understanding the performance implications of changes dictated by budget cuts
Informed decision making and better understanding of consequences of design
Built-in capability for facility adaptation to organisational change and growth over time, including recycling of facilities into new uses
Significant cost savings in the building process and throughout the building life cycle
Accountability for building performance by design professionals and owners
Long-term improvements in building performance
Improvement of design databases, standards, criteria, and guidance literature
Improved measurement of building performance thorough quantification
Source: (Preiser et al., 1998)
The Post-Occupancy Evaluation Process
The POE process model
The POE is a systematic and formal process; it can be carried out at different levels of effort and complexity; namely the indicative, investigative, and diagnostic levels. The process model can be applied to any type or scale of building. Within each level of effort there are further three phases: planning, conducting, and applying the POE. These three levels are distinct; they are not cumulative, meaning that each level has its own techniques and does not include methods used from the preceding levels. (Preiser & Vischer, 2005)
Levels in POE
Indicative POE provides an indication of major failures and successes of a building's performance. This type of POE can usually be carried out quite rapidly, from a couple of hours to one or two days at most. A few assumptions are made while the indicative POE is carried out, it presumes that the evaluator/evaluation team is experienced in conducting POEs and is familiar with the building type to be evaluated. The Data-gathering techniques used during the indicative POE are;
Archival and document evaluation - all documentation that is compiled and used during pre and post construction process, as well as any other significant documentation or reports that might have had an impact on the buildings safety records, accident reports, remodelling/repair records etcâ€¦
Performance issues - this looks at technical building performance issues regarding environmental concerns. In addition, they deal with functional appropriateness of health, safety, and security issues.
Walk through evaluation - after the performance issues have been tabled, a walk evaluation is conducted, covering the entire facility and addressing the issues raised earlier. The evaluators will also take note of any other characteristics that may require attention.
Interviews - are carried out with various employees, this will aid in indicating various successful and unsuccessful indicators within the facility. (Preiser & Vischer, 2005)
Investigative POE requires a larger number of resources, is more complicated, more time-consuming and can cover additional topics and in greater detail than the indicative POE. Usually an investigative POE is conducted when an indicative POE has identified issues that require further investigation in terms of a facility's physical performance and the occupants' response to it. The steps in conducting an investigative POE are identical to those of an indicative POE however the level of effort is intensified. (Darkwa, 2006) citing The literature suggests the an investigative POE generally requires 160 - 240 man-hours, plus staff time for support services , the extra time will spent on site to assemble more sophisticated data and analysis documentation. (Darkwa, 2006) Citing (Preiser & Vischer, 2005)
Diagnostic POE is a multi-method strategy which comprises of questionnaires, surveys, observations and physical measurements to exemplify an in-depth investigation conducted at a high level of effort and can be complex in nature. A diagnostic POE may take from several months to one year or longer to complete. As a result of the extended time frame the results and recommendations are long-term orientated, aiming to not only improve a particular building but also the state of the art in a given building type.
Strategic Assessment Management (2003) also refers to three levels of POE, namely the broad level, the detailed level and a combination of both the broad and the detailed levels. These levels are of a similar nature to that of (Preiser & Vischer, 2005) 's levels. The broad level can be compared to that of Preiser, et al., (2005)'s indicative level since entails a high-level evaluation. It uses fewer resources to that of the detailed level POE; and should be undertaken routinely on new facilities. The detailed-level POE entails an in-depth level of evaluation. This level of evaluation is usually more resource intensive and should only be undertaken on an "as required" basis. This level would compare to that of (Preiser & Vischer, 2005)'s Investigative level. The combination level is a mixture of a broad-level POE followed by a series of detailed-level POEs which form a highly effective POE strategy. In this strategy, the detailed studies are identified by the outcomes of the broad study. This results in the focusing of resources upon priority issues. (Darkwa, 2006)
Preiser & Vischer (2005) give a rough idea different phases and steps involved in conducting POE. These phases are made up of planning, conducting and application. These phases are all detailed by another two authors, namely (Strategic Asset Management, 1997); (Watson, 2003);
Table 2 - Phases involved in conducting a POE
(Preiser & Vischer, 2005)
(Strategic Asset Management, 1997)
Do reconnaissance and feasibility study
Preparation phase (2-3 weeks)
Draw up timetable
Initiating a POE
Define the scope
Select level of evaluation
Initiate on site data collection
Monitor and manage data collection
Interviewing Phase (1 week)
Develop data collection methodology
Select data collection instrument
Conduct and analyse the survey
Analysis and reporting phase (3-6 weeks)
Compile and present report
Implement actions and measure effectiveness
Source: (Darkwa, 2006, p.54)
Phases in POE
Each level within the POE is divided into three phases.