UK researchers have sparked debate on the cause of the gap between predicted and actual building performance, controversially pointing the finger at the people who model energy performance and labelling them “modelling illiterate”.

The accusation was levelled at building energy modelling professionals by University of Bath professor of low carbon design David Coley and colleagues earlier this month in peer-reviewed journal Building Services Engineering Research and Technology.

The story has caused consternation in the UK, following the research being picked up by The Telegraph, with at least one building modelling company complaining they had been made a scapegoat for what was a far more complex problem.

In the article Professor Coley described the study findings as a “serious scandal”, likening it to the VW emissions scam.

In the UK, both residential and non-domestic buildings are required to have an Energy Performance Certificate that estimates a building’s energy efficiency on a scale from A to G. Building energy modellers use a range of computer simulation programs to calculate performance, but have no legal obligation to ensure a building’s certificate corresponds to actual performance.

The system is like the Australian NatHERS system that rates the energy efficiency of a home based on its design, and which also suffers from a well-documented performance gap. A 2014 pitt&sherry report put this down to a number of causes, including dodgy builders, energy assessors and building surveyors, as well as a lack of proper oversight.

Energy use twice what is predicted

There are claims that measured energy consumption in non-residential buildings in the UK can often be more than two times what has been predicted at the design stage, which Professor Coley said had severe financial and amenity implications for building owners, and environmental implications for governments’ Paris targets.

He said previous research had assumed these differences could be attributed to the construction and operation stages.

“However, we have revealed a new cause for the ‘performance gap’, that being the modelling illiteracy of building modelling professionals arising from the modellers being separated from the rest of the construction process and the final building,” Professor Coley said.

The researchers surveyed 108 building modelling professionals on 21 design energy-related aspects of a building, including insulation, heating, glazing ratios, airtightness and ventilation rates.

The questions were based on an actual building – a typical UK semi-detached house that had been upgraded – in which detailed energy, occupancy and temperature data had been recorded pre and post refurbishment.

“Such a building, rather than for example a large office block, was chosen deliberately to reduce the complexity of the situation and hence improve the accuracy of the human judgements,” the study report said.

However, the respondents could not agree on which elements were the most and least important in terms of their effect on energy performance. Neither amount of modeller experience nor level of qualification had any effect on accuracy. In fact, a quarter of respondents were deemed to be no better than if a member of the public were selected at random to do the work.

A quarter of respondents were deemed to be no better than if a member of public were selected at random to do the work.”

Co-researcher Dr Ian Walker said given the findings that education or experience had no effect on predicted performance, governments needed to implement educational and policy change.

“Currently, an in-depth qualification for building modelling does not exist, meaning there is little formal training process for those entering the profession,” Dr Walker said.

“If this aspect can be addressed, part of the ‘performance gap’ could rapidly be reduced.”

Industry says story much more complex

3D performance analysis software company IES said while more needed to be done to address the gap, energy modelling professionals had been unfairly targeted.

“Yes, the ‘performance gap’ is well documented and known about in the industry,” IES communications manager Edwina Cramp said in a blog post.

“But to address it requires action by all those involved in a building’s lifecycle, from design to operation. That includes architects, engineers, energy modellers, contractors and facilities managers to name a few. The finger should not just be pointed only at building modelling professionals.”

UK Green Building Council director of policy and campaigns John Alker said the majority of buildings were not performing as expected, and agreed it was due to “a variety of complex reasons, and needs action by all those involved in the property lifecycle – such as architects, engineers, contractors and facilities managers – not just building modelling professionals”.

Ms Cramp said there were a number of industry initiatives working to reduce the gap and the “digital revolution” of the construction industry through Building Information Modelling (BIM) meant that “the industry has a vehicle to capture relevant information during design for use during the operational phase of the building as well as accountability for operational performance”.

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  1. Energy modelling is just that, Modelling. it is a prediction about the future. Pre-design modelling should only be used as a guide and inform decisions about things like building orientation and window type selection etc.

    Compliance with energy efficiency criteria is a different thing. A buildings energy rating should only be assigned once the building is built.
    Blower Door testing at completion is the norm in many countries. It provides owners with an accurate assessment of their building.

    If Blower Door testing was a compulsory stage of completion I think you would see a lot more attention paid to the claims made when modelling a building at design stage.

    1. Good point and one the industry is making since our article. Along with the important observation that you can design all the efficiency, you want into a building but what we really need is for buildings AND tenancies to declare publicly what their energy performance is. And this needs to be regularly assessed. No more hiding behind a design idea. It needs to be mandated now. We are so over hearing how hard it is to motivate second tier owners of buildings to save energy. They don’t want to, they don’t care. What will make them care is a stick and a carrot. Served at the same time. We KNOW from the Green Building Fund that financial inducements work for many. But a big fine works for all.

  2. What’s the point creating more building simulation programs that are not anchored on “real house” controlled simulation testing. That has been undertaken in the USA by a Climate Simulator at places such as ORNL in Tennesse, but even which ORNL could not account for “occupant behaviour”.

    Most importantly, why is it that there are never any Open Technical Forums in Australia, where anybody can attend to face one another and discuss?
    Such as the 2014 Pitt & Sherry report Townsville Building designers Workshop findings that, in the Tropics, no bulk insulation should be used in ceilings, and only reflective foil insulations. Really odd how dead silence prevails about this subject that I have highlighted on several occasions. Regulations are meant to be “evidence-based”. They most certainly are not.

    And to amplify the crisis, what is going to happen when the national power grid collapses from predicted power shortages next summer? Where are consumers meant to turn to for independent trustworthy thermal performance advice. It doesn’t exist. CSIRO have been gutted for funding over past 25 years (as revealed in the Royal Commission HIP) and depend on commercial contracts.

    Why are all solutions hidden away by so called HERS experts? They have all failed so far. You only have to read this Fifth Estate article and the earlier connected story.

    Well done for this brave story.

  3. This strengthens the argument to require all regulatory building thermal performance simulation to be conducted by professionals who are suitably trained and their professionalism audited by an accrediting body which also provides ongoing technical and professional support, such as the ABSA.

  4. I pray that the Fifth Estate have the fortitude to print the information below because the time has come, tens of millions of dollars that have be paid for by the taxpayers of Australia for fraudulent building energy efficiency that must be exposed.

    I completely take full responsibility for my comments, this my battle, not the Fifth Estate they are responsibly reporting my comments backed up by Dr Walkers article.

    To date any research for energy efficiency of residential building, or airconditioning ductwork that has been conducted in Australia, IS A FRAUD.
    Anyone, including Universities, that wishes to take legal action, AGAINST ME, I look forward to embarrassing you.

    Check out my 2014 Royal Commission Home Insulation Program papers on the net exposing the fraud of a CSIRO million dollar building energy efficiency research program that established very little.
    Google graemedoreian

    A prominent CSIRO building energy efficiency Dr may consider going on permanent leave.
    “A quarter of respondents were deemed to be no better than if a member of public were selected at random to do the work.”
    “Co-researcher Dr Ian Walker said given the findings that education or experience had no effect on predicted performance, governments needed to implement educational and policy change.”

    My Comments
    Computer modelling is a “job for the boys” aided and abetted by senior bureaucrats.

    No one can predict OCCUPANT BEHAVIOUR, this was established by Jeff Stein USA 1997.

    As I have said for years up until now, after meeting with over twenty senior bureaucrats and politicians, the only way to true energy efficiency in Australian homes, (because our climate is different, and we build homes different to other areas in the world) while still being able to provide a healthy internal environment is to have controlled climate testing of a base home before, and after improvements are made incrementally.

    NO WAY could any University, CSIRO be trusted to conduct any future building energy efficiency testing for residential buildings.

    I have a test program I developed, and can manage all aspects of that test program, signed off by an Australian Professor, one of Australia’s most Internationally experienced, prominent building energy efficiency Professors. BUT who cares.