Simulation are we just ticking boxes?

At Simulation are we just ticking boxes? Rokia Raslan from UCL spoke first about the variance in outputs from accredited tools. She used twelve tools, one modeller (herself) and three non-domestic building models.

One building model (the most complex one) failed the CO2 emission target using four of the accredited tools, highlighting the huge variance in results.

It also shows how accredited tools can also be used to get you the results you want for planning, compliance or an EPC. This large simulation variation contributes to the performance gap (linking nicely back to our previous lecture on the Performance Gap).

Roger Smith, from Parsons Brinckerhoff, was our second speaker argued that simulation isn’t just ticking boxes. As an organisation they use models from lighting and glare analysis to CFD to model airflow patterns and temperature distributions.

He spoke about offsetting heat gains through natural ventilation for London Underground substation upgrades. Natural ventilation was largely insufficient so they modelled the mechanical ventilation which enabled better heat dissipation. This use of modelling has saved the client money and allowed comparison of both solutions in this scenario at a much lower cost.

Greig Paterson spoke about modelling design for architects rather than engineers. He spoke about using artificial neural networks and machine learning techniques to model schools in England. If you are interested in getting into this area he suggested the Matlab tool kit is a really good starting place for these kind of models.

The models require hundreds of inputs gathered in a desk based study and look hugely complex, which Greig is trying to hide behind a simplified user interface to make it usable in his field.

While models are incredibly useful and can save cost I think it is important to recognise two things

  1. your model will only be as valid as your input data is (garbage in = garbage out).
  2. models should be used in conjunction with your common sense and engineering judgement to ensure we aren’t accepting the results as fact when there can be such variance.

The last in our series is tonight at UCL Energy Institute 6.30pm and looks at retrofitting, so we do hope to see you there. If you missed any of the YEPG summer series the presentations can be found on the CIBSE Young Energy Performance Group website.


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