Overheating investigation in UK social housing flats built to the Passivhaus standard

Global environmental and energy concern have led to rapid growth in construction of more energy efficient buildings. For this reason, Passivhaus standard as one of the fast growing building energy efficiency standard has seen growing interest in the UK building industry particularly in the social housing sector. While considerable research has been undertaken regarding the effect of Passivhaus standard in reducing heating loads, less attention has been paid to its annual and whole-life performance characteristics. The aim of this study is to evaluate and mitigate the risk of overheating in social housing flats built to Passivhaus standard across the UK. For the purpose of this study, the risk of overheating has been evaluated in existing social housing flats built to the Passivhaus standard. In addition, current and future risk of overheating has been investigated across four UK archetypical locations (London, Birmingham, Manchester and Edinburgh) using various design and occupant behaviour simulated models. Also, the influence of design and occupant behaviour parameters has been explored with relation to normal and vulnerable occupant types. Results from the case study indicates that considerable number of flats overheated during the monitoring periods especially in the case of vulnerable occupants and the impact of occupant behaviour on temperature variation found to be significant. Overheating risk in London is found to be the most significant and improving design or occupant behaviour in this location are shown to have no significant effect on avoiding this risk. Edinburgh and locations with a similar climate are the most suitable locations in the UK for developing Passivhaus flats, as current and future overheating risks are predicted to be negligible. Current overheating risk in other UK locations are shown to be low but considerable in the future specifically for vulnerable occupants. Hence, to ensure delivery of thermally comfortable dwellings, there is a need for careful design and thermal modelling simulation at the design stage as well as increasing occupants' awareness and run Post Occupancy Evaluation in order to promote appropriate user actions to reduce this risk. This study highlights that the control of solar gain through regulating glazing area, accurate external shading and appropriate glazing g-value have the most impact on reducing the overheating risk. However, it is notable that avoiding the occurrence of overheating through careful design or appropriate occupant behaviour is only achievable under certain summer condition within certain time scale and occupant types.