Post Occupancy Evaluation: operational performance of a refurbished office building

This blog was written by Dr Michelle Agha-Hossein BEng (Hons), EngD, Sustainable Building Consultant for BSRIA's Sustainable Construction Group

This blog was written by Dr Michelle Agha-Hossein BEng (Hons), EngD,
Sustainable Building Consultant for BSRIA’s Sustainable Construction Group

My Engineering Doctorate study aimed to investigate how and to what extent office building refurbishment can help to improve occupants’ satisfaction, perceived productivity and well-being while optimising building’s operational performance.

A case study approach and a “diagnostic” post-occupancy evaluation style of framework were adopted in this study to evaluate the performance of a recently refurbished 5-storey office building in detail and find opportunities to reduce the gap, if any. The study divided the workplace’s environment into three categories: ‘physical conditions’, ‘interior use of space’ and ‘indoor facilities’. Employee surveys and interviews revealed that interior use of space was the most important aspect of the building influencing occupants’ perceived productivity, well-being and enjoyment at work (happiness) while the improvement of the indoor facilities had no significant effect.

The study also concluded that issues with the physical conditions (such as noise and temperature) causes negative effects on perceived productivity but improving this aspect to a higher level than it is required would not necessarily increase perceived productivity. In contrast, improving the interior use of space aspect of a workplace would increase employees’ perceived productivity proportionally.  These results, however, should be considered with cautious as employee’s satisfaction surveys and interviews revealed that employees’ levels of expectation might have affected their levels of satisfaction with their new work environment.  This could cause some bias in the results of buildings’ performance evaluation. A potential

Old working environment

Old working environment

solution to this issue is to measure occupants’ expectations for their future workplace at the design stage to try to fulfil these expectations as much as possible. How well the new work environment met occupants’ expectations is another factor that should be measured at the post-occupancy stage.

It was also noted that the occupants density at the building was low at the time of the study (17.7m2/person) and that the space was not fully and effectively utilised and more than 50% of the workstations were often not in use. The link between improving space utilisation and the building’s energy consumption as well as its occupants’ perceived

New working environment

New working environment

productivity and well-being merits further investigation. These results are important in the projects where increasing productivity is a key and the budget is limited.

In terms of energy performance and CO2 emission, it was revealed that the actual emission of the building was three times more than the design target. Most of the low cost opportunities identified to reduce the gap were related to the building management and control as well as occupants’ behaviour. I will be doing a webinar very soon on simple energy efficiency tips related to building management and control and occupants’ behaviour. Watch BSRIA’s website for more details about this webinar. 

Emerging themes from Innovate UK’s BPE programme

This blog was written by Peter Tse, Principal Design Consultant for BSRIA's Sustainable Construction Group

This blog was written by Peter Tse, Principal Design Consultant for BSRIA’s Sustainable Construction Group

Back in May 2010, Innovate UK (formally TSB) embarked on four year programme, providing £8m funding to support case study investigations of domestic new build and non-domestic new build and major refurbishment projects.  In total the programme has supported 100 successful projects to provide a significant body of work, that provide insights on the performance of various design strategies, building fabric, target performances, construction methods and occupancy patterns, handover and operational practices.  This work will be shared across the industry providing evidence based information, increasing industry understanding to support closing the loop between theory and practice, ensuring the delivery of zero carbon new buildings is more readily and widely achievable.

Currently project teams are concluding their investigations and collating their findings, and dissemination of the results of the programme will begin in earnest in the first half of 2015.  However, as the programme has progressed, there are some consistent themes that are emerging.  Focussing on the non-domestic projects, I will address a couple of these emerging themes.

The first is around adopting innovative building systems to deliver low energy consumption and comfortable conditions, and unintended consequences associated with these technologies.  This covers a broad spectrum of building technologies including solar thermal, heat pumps, biomass boilers, earth tubes, rainwater harvesting, controls and natural ventilation strategies.  Innovation in its essence will have some inherent teething problems, which is often overlooked in the charge towards reaching our carbon reduction targets.  The obvious default stance is to specify proven and reliable technologies which are delivered by a team that is familiar with the technology, but our journey towards delivering true low carbon building in operation would inevitably be prolonged.

An additional level of complexity can be added with innovative systems; one healthcare facility introduced solar thermal and a combined heat and power (chp) unit, to supplement natural gas fired boilers for heating and hot water requirements. With several sources of heat complexity is added to the control strategy, trying to strike a balance between changing heat demands of the building and optimisation of the system.  This complexity, coupled with a requirement for increased operator understanding often leads to system underperformance.

The practicalities, maintenance and associated costs of innovative systems is seldom fully realised by clients.  An office reported success of the rainwater harvesting system, but were surprised at the frequency of filter changes to mitigate the system being blocked.  Another office had to regulate a fan associated with earth tube ventilation system, as running at a higher speed caused too much noise for occupants.  A school had ingress of water to an underground wood chip store rendering the biomass boiler idle for significant periods.  A hotel employed automatic external blinds which retracted in windy conditions to avoid damage, thus offering no shade to occupants during sunny, windy days.

DC-Innovative-Construction-Services-Building-Maintenance1It is clear a reality checking process is required for design decisions to mitigate such matters.  BSRIA’s Pitstopping guide, which resides within the Soft Landings framework describes a process that allows construction teams to periodically reconsider critical design issues by focusing on the perspective of the end user.  This also provides an opportunity for the client to understand the full ramifications of implementing innovative building systems for a more informed decision, and to align client expectations.

The second theme involves the process in delivering innovative technologies, with a particular a focus on commissioning and handover.  The commissioning period residing at the end of the build process is often susceptible to being squeezed.  When the decision has been taken to adopt an innovative building system, there is increased pressure during commissioning to ensure the system is operating as intended.  With the additional complexity associated with innovative technologies, it is vital the commissioning time is adequate to complete comprehensive scenario based testing; how is hot water delivered if the solar thermal does not provide a contribution, how is the building operator alerted the status of the system, how can the operator diagnose the problem, how long can the system operate without the solar thermal contribution without major detrimental effects etc.  To ease the burden on the commissioning period, it is clear commissioning should not be afterthought, but an integral part of the build process.

The commissioning period also signals a time where many of the stakeholders with tacit knowledge of the innovative building systems have changing responsibilities. It is vital this knowledge is captured for users before the opportunity is lost.  Building manuals, user guides and logbooks need to be completed so users can relate to their building environment, understand control of the environment and capture major alterations.

Figure 1 - South façade showing café, street and incubator office blockMany projects reported that guidance for both users and operators was often lacking, with several BPE teams developing guidance as part of their projects to support users.  Commonly BPE teams have also struggled to find initial design intent and operational strategy associated with innovative technologies, highlighting the importance of handover documentation.  Training of users is another key element to knowledge continuity, but several projects reported changes in staff being a core reason for innovative systems underperforming, as documentation was not kept up to date.  The value of clear concise user guidance is evident; BSRIA’s Building Manual and Building User Guides helps individuals responsible for creating building logbook and user guides.

In this blog, I’ve only addressed a couple of areas in regards to emerging themes, to hear more about findings from the programme, come hear me speak at the Energy Management Exhibition (EMEX), at Excel, London on the 20th November, 2014.  Additionally, join the BPE community at connect.innovateuk.org, and search for Building Performance Evaluation.

Design Fine Tuning?

 

Julia Evans, BSRIA Chief Executive

Julia Evans, BSRIA Chief Executive

BSRIA has been involved in many recent projects including an independent assessment of the realised performance of low energy / environmentally conscious buildings.  This includes projects associated with the Technology Strategy Board’s Building Performance Evaluation (BPE) programme.

The emerging results for more than 50 non-domestic buildings have now been analysed by BSRIA to look at what works well, and when things don’t, why this is the case.  It’s always difficult to generalise based on such a diverse building stock, ownership profile, procurement route, supply chain capabilities, and operational approach, but its clear that in many of the buildings there is a significant performance gap between design intent, and realised performance.  Analysis of such data is always a challenge.  How does one attribute, for instance, any shortfall in performance between the specification, design, construction, commissioning process, and to operational issues such as sub-optimal energy management and / or changes in operating regime such as an extension in occupancy hours.

However one lesson inferred from the analysis is that with some low carbon (and / or energy) buildings one of the unintended consequences is that sometimes the building has been finely “tuned” to minimise carbon (and / or energy), and capital costs at the expense of the building’s resilience in the face of, say, changing patterns of use or internal gains.  Put simply, if a building has been engineered to reduce energy and or carbon for a particular set of operating conditions, and one way of achieving this is to simply size ventilation, and air conditioning plant in line with those conditions, what happens if say internal gains increase as a result of higher occupancy loading?  In practice it is found that some environmental designs lack the flexibility to cope with changes in business use because of limitations built into their design.  This happens with more conventional buildings, with the difference for environmental buildings being more pronounced because the design in many cases is more finely “tuned” as we move ever closer to “near zero”, or “very low” energy / carbon buildings.

BSRIA’s experience identifies many of the good practices required to ensure environmental buildings work well, and also the impact of poor practice.  Overly sensitive design is one cause of poor performance in practice.  So the question is why do some clients and their design team include a sensitivity analysis to design services and size plant so as to ensure resilience, whereas others adopt an approach best characterised by “lowest capital, highest environmental ranking, never mind about actual performance in use”?  The likely answers are complex.  Those found by others like Latham and Egan come to mind for some instances: informed clients recruit supply chains who know their business, and both understand implications of design decisions; post-occupancy-evaluationanother is the chasm which can often occur between those who specify, procure, and lease buildings, and those who occupy and manage them.  Perhaps a third is that once a building has been occupied, too seldom is thought given to how the building will actually work in the face of changes in occupant requirements.

The question for BSRIA is how we can provide a steer and guidance to our members and the industry as to how best to ensure that we build the next generation of environmentally sensitive buildings to be even more resilient in the face of likely changes those buildings will face over their lifetime.  A building which has a very low carbon and / or energy design use, but which fails to provide a productive environment in the face of foreseeable changes in operating conditions can’t really be described as “sustainable”.

This blog was written by BSRIA’s Chief Executive, Julia Evans. For more information about BPE you can visit our website or visit the TSB’s BPE pages where you can look at case studies and methods of BPE (you may need to register to access these). 

Making buildings better – measuring for improved building performance

Andrew Eastwell, BSRIA CEO

Andrew Eastwell, BSRIA CEO

BSRIA has always been in the business of measuring, whether it is a physical quantity such as temperature or pressure, a market assessment such as volume of product imported to a given country or a softer, more management-orientated value such as a benchmark or satisfaction score. Measuring is a fundamental characteristic of our industry’s operations and it is in BSRIA’s DNA.

The need for accurate and more comprehensive measurement has been increasing in response to the revolution that is the low carbon agenda. Revolution is no idle description either. In just over a decade, carbon signatures of new buildings have been required to fall to “nearly zero” – yet few owners were even aware of their building’s operational carbon use at the start. In looking backwards over the past few years, I think BSRIA can be proud of its role in promoting the increased use of through-life measurement embedded in processes such as Soft Landings and the associated building performance evaluations.

There is another BSRIA process that is associated with the collection of measurements. This is the process that turns detailed, often randomly accumulated and frequently disconnected data and information into documents that can be used by our members to guide them in their work. A couple of decades ago this process was greatly enhanced by the availability of a managed construction research programme that not only contributed funds from central government but much more importantly brought focus and long term stability to the accumulation of knowledge. This stability was crucial since it enabled individuals to establish research skills and careers with enduring value to the sector they served. Loss of this programme has also resulted in a loss of cohesion between frontline companies willing to collaborate within the longer term research process.

There is a however a new kid on the block that may be about to revolutionise the traditional measure/analyse/publish process that has dominated research and guidance in our sector.

As disruptive technologies go, Big Data has managed to remain under the public radar quite well until the recent disclosures of the USA “Prism” project. Under Prism, colossal quantities of data harvested from both open and private sources are analysed to identify supposed threats to homeland security. It is the use of automatic analytics software combined with large arrays of sophisticated new sensing technologies that makes Big Data techniques so intriguing for the built environment sector.

By way of example, consider the problem of maintaining comfortable temperatures in a space. Traditionally we have used lab research on volunteers to establish what “comfort” requires. Ole Fanger took years to generate his widely used algorithms but they still do not cover all the possible variables that affect perceived comfort. We now use a thermostat, with a setpoint guided by Fanger, and assume that all is well with our occupants. In the new paradigm, cameras utilising facial recognition software will be capable of spotting yawning (too hot, too much CO?) or sluggish activity (too cold). This data is available for every worker in a given space and a “voting” system used to optimise comfort over the group.

But of course there is more. This data could be available from many sources in a Prism type environment. There would now be the potential to mine the data to establish new benchmarks feeding back to the design process that can be tailored to the particular activity type. Schools, offices, homes and shops each can be analysed not just to establish a single setpoint value but to understand in great detail the envelope or distribution of responses. At last, proper large scale data sets can aid our work – and most of what we need to do this is already available through installed BEMS.

There is one further gain possible from this approach. Traditional academic research leading to refereed papers and thence to institutional guidance can take half a working lifetime to complete. Big Data results can be achieved in hugely reduced timespans. Take the case of adverts you see on Google – these are tailored specifically to you based on purchase decisions you may have only made via unconnected sites a few hours earlier. Scary but true.

Big Data is where BIM, Smart Cities, performance contracting and responsive design meet. It challenges all the preconceptions of professional codes, cuts swathes through the notion of privacy and opens up “our” market for knowledge to an entirely new set of competitive players. The next decade is going to be seriously exciting and I am sure BSRIA will remain strong to its ethos of Measuring and Managing in this startling new environment.

BSRIA provides a range of services to conduct and support BPE, from the complete evaluation to providing energy monitoring instruments and benchmarking building performance.

Post Occupancy Evaluation – The challenges of a ‘greener’ future

I joined BSRIA as a Graduate Engineer in January 2011. Prior to this I was studying for my PhD in the School of Civil Engineering at the University of Leeds.

An Appraisal of the performance of a ‘green’ office building

A summary of my research is given below:

The challenges of a ‘greener’ future are now a responsibility for everyone. This is particularly so for the built environment, where sustainable building design is no longer an innovative option but more of a legislative must. Unfortunately significant differences are often found between the design and measured performance of buildings, with many factors contributing towards these discrepancies.

The research work investigated, using Post Occupancy Evaluation (POE) techniques, the credibility gap between design and measured performance of a partially occupied ‘green’ office building selected as the case study. The results found that the measured energy consumption was over three times the design estimates, and the performance compared poorly against good practice benchmarks for similar buildings. The study’s POE also revealed inefficient control settings, high out-of-hours energy consumption and ineffective building management.

This study went beyond a typical POE as it also includes investigations into how the occupancy variations, and the management strategies applied under these conditions, can impact on building energy performance through the use of simulation modelling techniques (IES<VE>). This is an area where very little research had previously been carried out. At the 50% occupancy levels found at the time the research was conducted, potential annual savings of over £30,000 in utility bills and 60% in energy consumption were estimated if more effective management and control was implemented.

Social-related aspects of building performance are also investigated. Occupant satisfaction and comfort surveys were conducted and the results were compared to previous findings. The perceived comfort and satisfaction with temperature was the most disappointing finding from the survey, however overall the building was comparable to the average benchmarks, but did not perform well when compared to other ‘green’ office buildings.

The study revealed the potential for the building to be fine-tuned to perform more efficiently than was at the time of the study, however there must be suitable, skilled Facility Management to ensure this is delivered.

For more information on Post Occupancy Evaluation/ Building Performance Evaluation…..

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