Achieving a better understanding of air infiltration when assessing overheating in multi-residential dwellings

In temperate climates the prediction of indoor temperatures using Building Performance Simulation (BPS) is thought to be highly sensitive to assumptions regarding convective and radiative heat transfer processes. This paper investigates whether the way in which infiltration is modelled may be exerting a pronounced effect on the results of overheating studies. An EnergyPlus model, of a dwelling in a multiresidential building in London, was created to investigate the influence of infiltration and exfiltration pathway assumptions on the prediction of overheating. Baseline modelling in accordance with the CIBSE TM59 methodology was compared to scenarios using best practice dynamic modelling procedures. The findings were compared to empirical data and show that the indoor temperatures are highly sensitive to how the infiltration airflow network is modelled. The results of this study provide practical guidance for modellers and building designers on what aspects to consider when creating energy models to ensure more reliable outcomes. Implementation of these findings is considered crucial for the further development of TM59 where reliable results are central to informing robust designs and preventing unnecessary overheating risks in future low energy building design.