Thermal performance of low-carbon prefabricated timber housing in the UK

The research investigates thermal performance of prefabricated timber housing in the UK due to a growing concern regarding the increase in summertime temperatures, which are expected to occur regularly as global temperatures increase. Furthermore, modern houses are built to meet improved regulations with additional insulation and are more sensitive to potential summertime overheating than older houses. This study examines three UK prefabricated timber housing developments (Bridport, Oxley Woods and Stadthaus) built in the last decade by evaluating the environmental conditions of the internal spaces and the occupants' comfort. The research employs a combination of different methods such as post-occupancy surveys, environmental monitoring, and thermal comfort surveys to assess the occupants' comfort in different seasons. Moreover, dynamic thermal modelling and simulations of the buildings to get more data over a long period are used. The outcomes of this study align with the research aim and sustain the research propositions. The research contributes to the on-going discussions on overheating in dwellings and provides first set of data on occupants' thermal comfort in prefabricated timber housing. Overall, Oxley Woods appears to be warmer than Bridport and Stadthaus. Using the adaptive thermal comfort model to evaluate the risk of overheating at the buildings suggests overheating occurs in 70% of the spaces monitored at Oxley Woods; while the analysis suggests warm discomfort in 50% of the spaces monitored at Bridport and Oxley Woods in the summer. The preferred temperature is 1.8ºC higher at Bridport than Oxley Woods indicating comfort is within a wide range for the occupants at Oxley Woods. The neutral temperature is higher at Oxley Woods by 0.8ºC suggesting higher adaptation of the occupants to the internal temperatures. The results from the research suggest the occupants of the houses with smaller internal floor area adapt better than the houses with bigger internal floor area. The occupants that indicate low level of control are less satisfied with the thermal conditions of the buildings. The results from the surveys and dynamic thermal simulations suggest that summertime overheating occurs in the buildings and high internal temperatures are likely to be more frequent in UK modern houses with reduced internal floor spaces than houses with increased internal floor spaces.