ESSAY 2
Learning from the Innovate UK building performance evaluation programme

Tom Kordel, XC02

In May 2010 Innovate UK began an £8m funding programme of building performance evaluation (BPE) studies for new buildings in the UK. In total 101 in-depth post-occupancy studies were completed on a range of domestic and non-domestic building types, with the aim of identifying the extent of and contributing factors to the ‘performance gap’. The studies involved project teams collecting design and in-use operational data in order to assess performance aspects such as energy, CO₂, comfort and occupant satisfaction.

This chapter discusses the programme’s findings, and next steps for BPE.

It is widely acknowledged that within the building industry a ‘performance gap’ exists between design potential and operational reality. In other industries, such a disparity between pre-purchase promise and actual performance would lead to recall and replacement. However, in construction, where feedback is often non-existent, few are held to account. As a result, our end product fails to improve.

It was with this performance gap in mind that Innovate UK launched an £8m, four-year programme of competitive funding to carry out BPE studies on new buildings in May 2010. The UK has set challenging targets to tackle climate change, starting with the goal of achieving an 80% reduction in carbon dioxide emissions by 2050, with an intermediate goal of 26% by 2020 compared to 1990 levels. With about 37% of the UK’s CO₂ emissions coming from buildings¹⁰ it is vital that we learn from our buildings in use, and use the findings to feed back into our design, construction and delivery.

The Innovate UK programme had four primary aims:

• to gain real-world performance data from recently completed buildings
• to enable the industry to learn more about the factors and variables that influence performance
• to embed a culture of building performance evaluation in the construction industry
• to generate a knowledge base of building performance case studies.

Under the Innovate UK programme, a total of 53 domestic projects encompassing 350 dwellings, and 48 non-domestic projects incorporating 55 separate buildings were successful in receiving BPE funding. These projects came from across a wide selection of typologies throughout the UK. Such a large and detailed programme of building performance studies has rarely been carried out, with few predecessors being publicly available and widely circulated (the PROBE Studies being a notable exception).¹¹

Project teams were led by architects, engineers, clients, consultants and contractors. All project teams consented to their buildings’ performances being made transparent and, as such, subject to scrutiny. In addition the project teams carried out much of the evaluation and analysis required themselves.

Successful applicants were fully funded to carry out either six-month early-occupancy or two-year in-use studies in order to gather data and assess their buildings’ performances with respect to:

• operational energy use and the associated CO₂ emissions
• thermal comfort
• occupant satisfaction
• reliability, maintenance and maintainability
• usability of controls and building management systems (BMS)
• low- and zero-carbon technology.

In order to support the participants and improve the quality and consistency of output, a panel of Expert Evaluators was formed. Projects were split between individual evaluators, who oversaw each study from start to finish.

Common themes from the programme

Innovate UK Expert Evaluators assessed the findings across the programme.¹² This included comparing key data such as measured and Part L (Building Regulations on energy use) predicted annual CO₂ emissions, as well as identifying where more qualitative findings occur on several projects. A number of common themes have emerged, summarised below.

Energy consumption is often much higher than design calculations suggest. Standard Assessment Procedure (SAP) and Simplified Building Energy Model (SBEM) are not meant to accurately predict energy in operation. However, the scale of disparity (actual emissions were 1.7–9 times the Building Regulations emissions rate, with an average of 3.7 times higher across the non-domestic projects within the programme)¹³ is significant (see Figure 01). The failure of compliance tools to account for the complexity of human behaviour and the imperfect reality of an occupied building accounts for only some of this difference. Much of the gap is a result of failings across the entire building process, from initial design, to construction, through to operation and maintenance.

Low-energy regulations and incentives can influence system complexity. Many of the projects involved in the programme were constructed with low-carbon ambitions, whether motivated by mandatory planning conditions (e.g. BREEAM or Code for Sustainable Homes ratings), financial incentives or voluntary factors from progressive clients. These low-carbon design targets are linked to compliance tools; frequently the tool is misused for design purposes, which leads to unnecessary complexity. For example in one project, a ground-source heat pump (GSHP) was deemed to create a significant enough CO₂ saving in SBEM that including it would trigger a financial incentive that allowed it to be installed for free. The GSHP was integrated into a design already including biomass boilers, gas boilers and mechanical ventilation with heat recovery (MVHR). Subsequently the building has experienced high energy use that is partly a result of uncertainty over the complex control strategy for the building’s multiple systems.

Lack of post-occupancy data means buildings may not be equipped to operate efficiently. There was difficulty in undertaking a large number of non-domestic BPE studies due to inadequate data: missing building log books, incomplete operation and maintenance (O&M) manuals, and omitted commissioning certificates. However, the greatest difficulty arose from the quality of sub-metered energy data. Insufficient metering, un-commissioned and low-quality meters, and inaccurate or absent logging systems proved to be commonplace. Unfortunately, the standard of sub-metering affected the programme; a number of projects had to be modified or requested time extensions in order to rectify metering systems. Once corrected, the metering and monitoring systems did provide the data needed to measure performance, identify energy waste and begin to optimise a building’s performance. However there remains a significant shortfall in the sub-metering being delivered, which creates barriers to improvement within individual buildings.

Innovation requires care and attention pre-and-post construction. A number of the projects incorporated innovative building systems such as earth tubes, automated natural ventilation controls, night cooling, hot water heat recovery and others. Such systems offer potential for improved performance but also carry a certain amount of risk to inexperienced design teams, contractors and clients. It is important to consider the commissioning and maintenance requirements of such systems as well as the detail of how they will integrate with more standard building features. For example, in one project an automated natural night ventilation system created an unexpected maintenance burden because of the large amount of mechanical actuators. In another, the night ventilation strategy was deactivated as a result of loose office paper setting off security alarms. This was an unforeseen impact that could have been avoided with a different initial design of the security system.

01 Ratio of Actual CO₂ emissions/m²/yr to Building Emission Rate Estimate.

Handover and commissioning is a necessity, not a luxury. Commissioning was given as a common reason when tracing the route of an in-use problem back to its source. Examples included presence-controlled lighting that rarely turned off, CHP engines that rarely turned on, sub-meters reading zero and MVHR systems that failed to supply sufficient fresh air to new dwellings. The simple solution to these types of problems is to ensure that commissioning is carried out properly; the reality of the situation is that a client’s rush to occupy often prevails. With an overrun in construction, a squeezed or compromised commissioning and handover period seems like the only workable solution. The programme has shown that such a decision can have significant consequences on operational energy, utility cost and occupant comfort that stay with a building for years to come, far beyond practical completion. This occurs even in instances where BREEAM credits for seasonal commissioning have been awarded. The importance of this period of calibration and fine-tuning both pre-completion and in early occupancy cannot be overstated, yet this phase of the project is so often hurried or ignored altogether.

Provide users with controls that are useful and intuitive. Controls take many forms in buildings, from automated weather compensation and complex building management systems (BMS) to common rocker light switches and simple window handles. Inevitably, as buildings integrate often-unavoidable technology and innovation in the quest for CO₂ savings, controls become complex. Poorly designed control strategies can lead to high energy use and poor comfort. This was particularly the case with BMS where, in many cases, they were not used in operation due to faults, limited handover and absent user manuals. A small number of simple controls seems to be the most successful strategy. Intuitive interfaces that focus on the most common use of the control, rather than trying to provide for every eventuality, are also important.

Building fabric is getting better but there is more to do. As part of the programme, pre-completion domestic projects were required to carry out airtightness tests, infra-red thermography and co-heating tests. The results of these projects suggest that the thermal performance of building fabric has improved with the inclusion of maximum U-value and airtightness standards within Part L of the Building Regulations. However in many cases, the results of the on-site testing fell short of the standards they set out to achieve. In particular, significant thermal bridges were clear on some projects, and unintended air leakage paths on others. Many of the issues found could be alleviated and high thermal performance standards achieved through the use of clear and comprehensive drawings and the presence of an experienced site manager.

Overheating is a significant risk that is not being addressed effectively. Thermal comfort monitoring was a mandatory part of the programme for buildings in operation. The monitoring results indicate that overheating is commonplace and most evident in domestic properties, with a variety of design and operational factors contributing to this effect. The design of glazing, natural ventilation, shading, MVHR, closed communal corridors and heating systems all need to be considered holistically in order to address overheating. The heightened risk of overheating in UK homes has also been highlighted in research carried out by Zero Carbon Hub, and is summarised by Gething in Chapter 3.¹⁴ Overheating is a problem that will get worse with the effects of climate change and must therefore be treated as seriously as fabric heat loss has been previously.

Lessons for carrying out BPE

The BPE studies within the programme are unlikely to be replicated at the same level of detail in the future without similar external funding. However, the benefits of a study can be repeated, through integrating BPE tasks into design and construction programmes, distributing responsibilities among typical project team members, and prioritising the BPE techniques that are most useful to the team – and, more importantly, to the occupants – so that feedback on performance of the building can be gathered in use.

Fabric performance techniques such as airtightness, smoke pen tests and infrared thermography are most useful when staged at the point in construction when fixing faults would be least expensive. This is particularly important when inexperienced project teams aim for best-practice fabric standards such as those within Passivhaus.

Checks and verification of the accuracy of metering and monitoring equipment must occur prior to contractors and the relevant subcontractor leaving the site. Metered data is the primary basis for optimising a building in use, and without it building or facilities managers have no hope of achieving the design targets for the building.

Data overload when analysing large data sets is difficult to avoid, and therefore a progression of analysis should be followed, from high-level through to fine detail. Evaluators should begin with annual utility data for benchmarking against industry standards such as CIBSE TM46¹⁵ before assessing monthly, then weekly and finally daily energy profiles. Profiles for unexplainable or inefficient behaviour should be assessed before digging deeper into each issue identified. Detailed analysis such as correlation with user profiles and BMS data or further on-site testing should be used for individual problem solving rather than from the outset of a BPE study. The same is true when considering comfort and occupant satisfaction. A high-level occupant satisfaction survey can help to identify areas of a building with comfort problems prior to carrying out detailed temperature, humidity and air-quality monitoring.

BPE requires the collation of qualitative data and not just the recording of quantitative data. Qualitative information obtained through interviewing occupants and project team members is invaluable in understanding why problems identified through the study have occurred. Informal conversations with occupants and, in particular, building managers, can help to identify any performance problems with a building far more quickly than data analysis in a spreadsheet. When conducting such interviews the interviewer should be independent from the design or construction team. Interviewees are then more likely to be honest and outspoken, and the evaluator’s judgements will not be influenced by the history of the project and its relationships.

A crucial factor in implementing the changes that come out of BPE studies in non-domestic buildings is the level of engagement of the building manager or facilities management team. The most successful studies were those in which the building managers were active in the BPE study themselves, and where a willingness or incentive exists to enact change and improve comfort or reduce energy use. If BMS are impenetrable or handover is lacking, this task becomes significantly more difficult and the tendency is for settings to be altered to guard against failure. Systems that require more sensitive adjustment in early operation, such as biomass boilers or an automated natural ventilation system, may be switched off. When this happens, the expected design CO₂ savings disappear. When carrying out a BPE study it is important to get the building manager on board, as they will have greater insight into how the building is actually operated as opposed to how it was designed to operate.

The future of BPE

The programme has amalgamated the data captured into a central and accessible format which is available online through the Building Data Exchange.¹⁶ By being freely accessible the platform allows meta-analysis by interested parties looking for robust evidence and data, stimulates the crossover of digital technology into the built environment and facilitates opportunities for data-driven innovation.

Since the Innovate UK BPE programme began in May 2010, there have been significant changes across the building industry, which may encourage greater uptake of BPE in the future.

These industry initiatives should encourage the uptake of BPE:

• The RIBA Plan of Work 2013 has been unveiled, with the new Stages 0 and 7, which will encourage project teams to review feedback from previous projects and carry out POE activities respectively.¹⁷
• Government Soft Landings has been introduced, which will ensure that public buildings follow a framework that focuses on the operational outcome of each building with clear requirements for improvements in handover processes, commissioning and elements of BPE.¹⁸ The original BSRIA Soft Landings¹⁹ is also becoming more widely used and is now referenced in Part L2A 2013.²⁰
• CarbonBuzz was launched in June 2013. The free online platform will encourage project teams to share energy data and building information in order to create better benchmarks and highlight the performance gap.²¹
• Performance in-use targets such as pursuing a Display Energy Certificate (DEC) ‘A’ rating are becoming more common, particularly in the public sector. In-use targets act as a useful way to focus design and construction teams on operational outcomes rather than design aspirations.²²
• CIBSE launched TM54 in September 2013. The publication provides users with clear guidance on how to evaluate operational energy use more accurately at the design stage.²³
• The updated BREEAM 2014 includes a number of credits that directly relate to BPE activities and should encourage their uptake in the future.²⁴

However, it is up to the traditional design and construction teams to drive a culture of feedback so this becomes the norm rather than the exception. After all, an industry that does not learn from its end product is blind to true innovation.

There have been multiple positive and negative findings from each and every project, but one consistent comment from all who took part is noticeable: there is both a need and a desire for all to carry out more BPE in the future.