Post-occupancy and indoor monitoring surveys to investigate the potential of summertime overheating in UK prefabricated timber houses

A post-occupancy evaluation was carried out in three prefabricated timber housing developments in the UK to identify the potential of summertime overheating. All the case studies selected are recipients of various low-energy or sustainability awards built within the last eight years. Two of the case studies are modern multi-storey apartments blocks (Bridport and Stadthaus) and the third one (Oxley Woods) a housing development with ten different prototypes. A paper-based questionnaire to assess how the indoor occupants perceive and rate the overall thermal environment and use control was administered. In order to evaluate the actual performance of the case studies, indoor measurements of environmental parameters and thermal comfort surveys were conducted in Bridport and Oxley Woods during summer 2012 and in Oxley Woods only during winter 2013. A total of 65 questionnaires were collected during the post-occupancy survey, while 141 and 161 questionnaires were collected during the summer and the winter indoor monitoring surveys respectively. The paper focuses on the findings of  post-occupancy and indoor measurement surveys. The post-occupancy survey suggests that there is a potential of summertime overheating in prefabricated timber houses, as more than 70% of the respondents feel ‘warm’ and ‘hot’ in the summer. Comparing these with the monitoring, it appears that the indoor temperatures tend to rise above comfort range when external temperature is above 19ºC, when only 10% prefer not to be ‘cooler’ in summer. Occupants are subjected to temperatures above 28ºC in living areas for more than 1% of total hours occupied between 08.00-22.00, while they experienced temperatures above 25ºC in living areas for more than 5% between 22.00-08.00.