Engineers blast uni's energy modelling study

A leading consultancy has launched a withering attack on a university’s report into energy modelling, labelling the findings of the research “deeply flawed”.

The University of Bath undertook a survey of 108 building modelling professionals and claimed to have found a new cause for the ‘performance gap’ – the difference between how much energy a building is predicted to use and how much it uses in reality.

It said such gaps have been attributed to how buildings are constructed and operated. But instead the report blames the ‘modelling illiteracy’ of the building modelling professionals themselves.

The report found that modellers often could not even agree on which aspects of performance, such as the amount of glass provided in a building, were important. And the researchers concluded that those carrying out modelling rarely discovered how their calculations related to the performance of the building once in use.

It said: “Building modelling professionals have blamed everyone from the builder not installing insulation correctly to the occupants leaving the lights on, but have never asked if they might be part of the problem.”

The report commends that performance gaps could ‘rapidly’ be reduced by improving the formal process for training process for those entering modelling profession.

“The impact of the inaccuracies of building modelling professionals has severe financial and environmental implications for both the government’s global warming targets as well as building owners who are purchasing homes and other buildings that are sold to be energy efficient but in reality are not,” said one of the report’s authors, Professor David Coley.

But Alan Fogarty, a partner at engineering consultants Cundall, dismissed the findings. While there was likely to be a performance gap in terms of how well the building has been constructed, “the suggestion that the design calculations are underestimating actual performance in use is nonsense and shows a lack of understanding of the calculations”.

The report’s researchers had shown themselves to be unaware of issues around energy consumption, claimed Fogarty, adding that the survey did not make clear how many of the 31 respondents were suitably qualified engineers.

“Bath University has shown itself to be ignorant of these complex issues and as a result have added credibility to the performance gap myth and pointed the blame at engineers,” he said.

Responding to the criticism, Coley said he welcomed having a debate on such an important topic, but he disagreed with Cundall’s assessment.

“Modelling is used for a lot more than compliance. It is often at the core of the design process, and therefore the knowledge of the modellers about the relative magnitude of the impact of changes to the design is very important. 

“Our approach has been used in many fields; it was a statistically sophisticated version of asking simple questions to a group of professionals and seeing if they gave the same answer. We gave a relatively simple building to a group of modellers and discussed the relative impact of errors in the known value of an item or the impact of small changes in the construction or use.

“We wanted to know whether modellers would in general agree amongst themselves and whether what they said was accurate, as measured by a verified thermal model of a real building.”