Jan L. M. Hensen
Robijnring 30
5629GK, Eindhoven
+31 6532 30 382
Region: XIV
Honorarium: None
Building Performance Simulation – mind the gap

The energy performance gap refers to the difference between expected (during design) and actual energy performance of buildings. There is significant evidence to suggest that this gap is getting larger as buildings become more energy efficient. There appear to be three kinds of reasons for the energy performance gap. The first is misinterpretation of regulatory compliance calculations as predictions of in-use energy consumption. The second kind is related to issues with the actual operation of the building (services), such as undetected faults and non-optimal controls. The third kind has to do with discrepancies between design stage assumptions and reality during operation of the building. Examples of the latter kind are incorrect assumptions regarding actual occupant behavior, on-site weather data, unregulated sources of energy consumption (e.g. plug loads, server rooms, external lighting), and performance of innovative building components. The presentation will discuss and illustrate the first and second kind in some detail, but the main focus will be on the third kind. The presentation will also argue and demonstrate that it is often more effective and efficient to get better assumptions rather than to use more complex simulation models. The presentation will finish with a brief introduction of the use of simulation models during the operation of buildings; e.g. as a digital twin for fault detection and diagnosis or for (model based) control optimization. Where appropriate, the presentation will highlight ASHRAE’s achievements and ongoing efforts in these areas.

Building Performance Simulation – challenges and opportunities

The lecture will start with a general view of the background and current state of computational building energy performance simulation in the context of energy efficient buildings and districts. It will then discuss the currently most common application of building simulation which is for code compliance checking. However, when used appropriately building performance simulation has the potential to help reduce the environmental impact of the built environment, to improve the indoor environmental quality and productivity, as well as facilitating future innovation and technological progress in construction. For that to become widely available, the building simulation community still has to overcome several challenges both in terms of technology and application methodology. Several of these challenges relate to the need to provide better design support. Issues include early phase design support, multiscale approaches (from construction detail to district level), uncertainty and sensitivity analysis, robustness analysis (employing use and environmental change scenarios), optimization under uncertainty, inverse approach (to address "how to" instead of being able to answer "what if" questions), multi-physics (particularly inclusion of electrical power flow modeling), and integration in the construction process (using building information modeling (BIM), process modeling, etc). Another group of challenges relate to the need to provide support for building operation and management. Here the issues include accurate in-use energy consumption prediction and model predictive control. The presentation will highlight ASHRAE’s achievements and ongoing efforts in these areas.