Summertime comparative evaluation of indoor temperature and comfort in Auckland New Zealand: a survey of green certified, code and older homes

A frequently stated hallmark of certified green homes is that they are 'healthier' and provide superior thermal comfort. This usually requires increasing insulation levels from code requirements on the understanding that this will provide a warmer, drier internal environment. However this solution to 'cold and damp' housing may have unintended consequences; while highly insulated dwellings may be warm over the winter, are they still comfortable during warmest months? This study analyses 29 dwellings in Auckland, New Zealand to determine if there is any difference in the temperature and thermal comfort between three types of dwellings: newly built green certified (6-Homestar), newly built non-certified and old dwellings (pre-1978). The results show large differences between dwelling categories with the certified 6-Homestar dwellings exceeding the World Health Organisation (WHO) healthy temperature threshold 75% of the time during the warmest months of the year, resulting in predicted occupant discomfort 16% of the time. These results have significant policy implications with it apparent that not only under-heating but also overheating require specific attention in government legislation, green building rating tools and building codes.