Empirical assessment of indoor air quality and overheating in low-carbon social housing dwellings in England, UK

New low-carbon houses are designed to reduce heat losses through improved airtightness and increased insulation, raising the risk of overheating and inadequate ventilation. This paper examines the overheating risks and indoor air quality (IAQ) of three sustainable social housing developments in England (UK), by conducting building performance monitoring and post-occupancy evaluation of six case-study dwellings. All the developments have been designed for Code for Sustainable Homes Levels 4 and 5. The case-study houses cover a variety of forms and different types of construction systems, but have similar occupancy profiles. Monitoring data on environmental conditions, IAQ and window/door opening are cross-related with the performance of fabric and systems as well as occupants' understanding, habits and behaviour. Findings indicate that indoor environmental conditions and air quality are determined by the performance of building fabric and systems as well as interaction of occupants with them. High indoor temperatures during summer are linked to window opening patterns and faults with underfloor heating system. While poor IAQ is linked with insufficient fresh air supply from the Mechanical Ventilation with Heat Recovery (MVHR) systems due to inadequate commissioning of the systems, coupled with lack of user comprehension in operating these systems because of poor guidance and inadequate user training. The findings reveal that there are interrelated socio-technical factors that determine the IAQ and occurrence of overheating in low-energy housing.