Modus

The benefit of hindsight: Post-occupancy evaluation

Post-occupancy evaluations could help create better, more resilient buildings so why is the wider industry yet to wholly embrace them?

Author: Stephen Cousins

17 April 2020

Illustration by Neil Webb

Illustration by Neil Webb

The world of low-carbon construction is fast-paced, with new materials and technologies constantly evolving to deliver greater efficiency and reduced emissions. Which makes the need to monitor how completed buildings actually function in use arguably more important now than ever before.

Experts frequently refer to an "energy gap", the discrepancy between the design specification for building performance and real-life performance in operation. Recently, post-occupancy evaluations (POEs) have emerged as a key methodology to bridge the divide.

POEs have been used in one form or another since the 1960s, and widely recognised approaches include the Building Use Studies (BUS) methodology and the Building Research Establishment's Design Quality Method (DQM). These aim to rigorously evaluate buildings after they have been occupied for a period of time to reveal information on technical, functional, social and economic performance and the impact on occupants' health and wellbeing.

"The industry is suspicious of post-occupancy evaluation because it could be used as a stick with which to beat people" Chris Jones MES Building Solutions

Design professionals can use the insights gained from such evaluations to tweak systems and improve performance and the user/occupant experience, or to inform the design and construction of future projects.

As Dr Ed Suttie, director of strategy and innovation at the Building Research Establishment Group (BRE), explains: "Many buildings do not perform as planned –  in some cases this can impact on running costs, staff and client satisfaction and performance, health, safety and comfort. For repeat construction clients, learning from and correcting past mistakes in the design and commissioning of buildings can be extremely cost-effective and improve workplace business outcomes. Understanding how buildings function and operate from the occupant and user perspective is at the heart of POE."

Awareness of POE and its benefits is on the increase. It has become mandatory on some public projects. However, the wider industry has so far failed to consistently embed it into construction procurement.

Part of the problem is the lack of an incentive for design professionals to question the performance of buildings after commissioning. Some may fear that exposing design errors could result in liability or litigation. The retrospective nature of POEs also requires buy-ins from building users and occupants.

"The UK construction industry is very protective and suspicious of this kind of investigation because it could be used as a stick with which to beat people," says Chris Jones, technical director at RICS-regulated consultant MES Building Solutions. "There is also the question of who pays the developer, the architect, or the building owner or client?"

"A better functioning building is better aligned to the intended tasks of its occupants, which can yield better business outcomes" Dr Ed Suttie BRE

Transforming attitudes means raising awareness of the positive role that POEs can play in delivering more resilient and futureproof buildings.

A legislative driving force for POE in Europe is the sustainable buildings agenda. The EU's Energy Performance in Buildings Directive (EPBD) established minimum energy requirements for new buildings and large renovations, and its subsequent reworking, in 2010, required member states to produce action plans to increase the number of virtually zero-carbon buildings.

Compliance with these regulatory requirements and standards can be articulated through a POE regime in conjunction with other certification systems, such as the German Sustainable Building Council (DGNB), or Building Research Establishment Environmental Assessment Method (BREEAM) in the UK. BREEAM offers credits for projects that implement a POE. Indeed, projects seeking a BREEAM rating, or WELL certification, are required to submit evidence of on-site, post-occupancy performance testing.

Detecting design drawbacks

Another benefit of a POE is that it can pick up flaws in sustainable design. The way different materials and building systems interact can trigger serious environmental problems for example, some airtight properties have suffered from damp and poor air quality while some highly insulated, lightweight buildings are prone to overheating. Other environmental issues may be revealed, too, such as fluctuating temperature, glare, poor acoustics, ineffective lighting or layouts not suited to occupier needs.

POE can drive big improvements to economic and social value, says Suttie. "It can help identify where maintenance and operational costs might be fine-tuned ... A better functioning building is better aligned to the intended tasks of its occupants, which can yield better business outcomes in an office, better educational experiences in a school and better healthcare outcomes in a hospital." In addition, healthier, more comfortable environments can lead to higher occupancy rates and, therefore, a more secure income stream.

As concern for health and wellbeing becomes mainstream in real estate, outcomes are shifting from aspirational to tangible measurements of performance.

Environmental sensors can record quantitative information such as air quality, thermal comfort and lighting levels, but an arguably more reliable form of feedback is the people using the space.

POE surveys can capture opinions on how well a space meets users' requirements and correlate subjective experience such as thermal discomfort with objective data about temperature or humidity.

"POE tells you the occupants' response to those environmental conditions and the layout and design of a specific building," explains Suttie. "This reveals so much more about the function of the building and opportunities to improve."

Specialist surveying skills

Architects often want to take charge of POEs to drive sustainable performance and ensure lessons learned are incorporated into future projects. But RICS professionals may be better placed to perform the work, says Jones: "Surveyors are a logical choice, as the assessment requires a broad skill set, including an understanding of building principles, of building pathology, and the ability to identify the causes of issues in a building. Surveyors have an analytical approach and know how to interpret things that others wouldn't notice; architects aren't necessarily ideally placed to do that."

Some POE techniques can only be undertaken by trained facilitators, others, such as the Building Services Research and Information Association (BSRIA) soft-landings framework, must be executed by the project team, while the BUS methodology is licensed through a network of partners trained to carry out surveys and interpret the results.

Information on current best practice for pre- and post-occupancy evaluation can be found in the new BRE publication Creating positive spaces by measuring the impact of your design, which was written to educate professionals, including RICS members, on POE's role in creating sustainable buildings.

"We should do this on every project now, and we should have been doing it for the past decade," argues Jones. "With heightened concerns about the climate and changes to building regulations driving us towards more energy efficient and environmentally robust buildings, POE is becoming a much more critical tool. I urge you to go out, get a qualification and become part of the future."

WHAT IMPACT HAVE WHOLE LIFE CARBON (WLC) ASSESSMENTS HAD ON THE SECTOR

In 2017, RICS published Whole life carbon assessment for the built environment, making whole life carbon (WLC) assessments of construction projects mandatory.

RICS professionals are required to consider embodied carbon for every build, as well as compulsory operational carbon measurements, and to deliver a consistent WLC assessment implementation plan and reporting structure for projects. The process is now widely used by major developers.

Simon Sturgis, founder of consultant Targeting Zero and co-author of the WLC assessment, told Modus: "The RICS document is specifically referred to in the Mayor of London's environmental statement of May 2018 and it will be referenced as a required methodology in the Greater London Authority's new London Plan, Policy SI2. It is also referenced in official guidance by RIBA, the UK Green Building Council and the London Energy Transformation Initiative, among others."

RICS runs the Building Carbon Database as a free resource for professionals to benchmark designs against embodied carbon data. 

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