Proactive post-occupancy evaluation

This is a part of the High-performance buildings feature

By Eziaku Rasheed, Dr Nimesha Vilasini, Achini Weerasinghe and Dr James Rotimi - 1 August 2021, Build 185

A digital post-occupancy evaluation system for checking the operational performance of commercial buildings will be a useful tool as New Zealand faces the need to meet stringent carbon targets.

THE WAVE of COVID-19 across the globe and decades of underperforming buildings in New Zealand have made better-performing buildings essential to improve the wellbeing and comfort of users.

As we spend about 90% of our time indoors, the role occupants play in a building’s performance is significant.

How we interact with our spatial and physical indoor environment determines the energy use and the effect of the environment on our comfort, health and even productivity.

Both comfort improvement and emissions reduction

As we gear up towards contributing to New Zealand’s 2050 zero-carbon goal, the need to prioritise energy efficiency in buildings is increasingly necessary to reduce emissions. While on-site building construction is the known offender, operational energy use is the silent yet long-lived contributor to emissions.

Buildings are designed and constructed to meet the needs of potential users, and how they operate influences occupant comfort and wellbeing. As well, the energy used to run building systems such as heating or cooling and lighting depends on users’ comfort expectations.

Offices perform below expectations

Despite efforts put in to delivering high-performance buildings that are energy efficient and beneficial to users, our office buildings perform worse than designed or projected post-occupancy. There is no objective evidence showing that office buildings perform as or better than designed irrespective of their sustainability status.

There seems to be a disconnect between the sustainability status of New Zealand office buildings and their actual performance.

There are two plausible reasons for this:

The lack of a systematic and holistic evaluation of buildings during operation.
What the post-occupancy evaluation (POE) is used for and how it is carried out.

Lack of evaluation during operation

POE is an essential measure of how a building ranks against key performance indicators. It identifies performance improvement opportunities in the design and day-to-day operation of office buildings. Whereas other building industries have recognised the importance of a systematic POE as an essential part of a building contract and embedded it in the design and procurement process, the New Zealand building industry is yet to do so.

In the UK, the Royal Institute of Architects Plan of Work 2020 requires POE during the handover and use stages and for all architects to promote POE to clients as a core service.

While routine check-ups are carried out on building systems in New Zealand as required by the building’s warranty of fitness schedule, a holistic POE that includes users’ experience and interaction with their buildings is lacking. Specifically, users’ interaction with their office environments is seldom considered important.

However, research shows that comfort-related actions by users have a significant impact on building performance and energy use. The consequences include building designs that do not reflect the diverse user characteristics and expectations unique to New Zealand work environments.

Consistent complaints about the negative impact of poor-performing buildings indicates that this issue requires attention. Often, in a bid to rectify these issues, measures taken result in high operational costs.

What and how of POE

At present, most POEs in New Zealand are carried out only when a retrofit is required or when rating credits such as NABERSNZ and the new NZGBC Green Star – Performance are targeted. Building owners are yet to understand the importance of conducting regular POEs as part of the building life cycle that include:

identifying and finding solutions to problems
informing future projects – providing a double-loop learning model
providing useful benchmark data for future projects.

With most POEs, there is a high dependency on users’ perception retrieved via questionnaires and interviews. These tools are useful as they indicate how users perceive their office environments.

While interviews are more rigorous and demand direct communication between the interviewer and the person interviewed, questionnaires are typically less in-depth. In addition, they cover more people within a short timeframe.

However, perception-based evaluations are marred by various biases and accuracy-based errors.

At best, they provide a large-scale indication of how users think their buildings perform but remain an indication and not an actual assessment of performance and how users behave.

Case for a proactive POE

As workers become more diverse in their needs, their comfort expectations in office environments are likely to change. The design and operation of spaces will need reviewing along with a requirement that our buildings contribute to New Zealand’s 2050 carbon target.

A proactive POE is needed – a robust, systematic and standardised POE protocol to improve existing building performance and influence future building designs.

According to the Royal Institute of Architects, while undertaking POE adds 0.1–0.25% to a project’s cost, it reduces long-term operational and maintenance costs associated with heating, cooling of indoor spaces and space management. As an example, POE carried out on an office building resulted in refurbishment and a 69% reduction in total energy use per desk space.

The Royal Institute of Architects suggests a graduated approach to POE that includes:

a light-touch review – by the end of the 12-month defects period
a diagnostic assessment – during year 2 of occupation
a detailed investigation by the end of year 3.

This is similar to the three-stage POE (indicative, investigative and diagnostic) for schools suggested by the Ministry of Education, yet the commercial sector is yet to institutionalise POE.

Work on new user-centric POE protocol

At Massey University, researchers are working on a novel POE methodology that will provide a digitised user-centric POE protocol that monitors and predicts long-term users’ energy use and comfort behaviour without the inaccuracy of traditional methods.