The Thermal Indoor Environment of Danish Detached Houses—Past, Present and Future

Danish detached houses have shown a new tendency in terms of the thermal indoor environment. On 13.4% of houses built after 2000, problems regarding overheating have been reported by the owners. In addition to this, we stand before climate changes resulting in rising temperatures, which will increase the problem of overheating in the indoor environment even further. Since 1979, the energy requirements of the Danish Building Regulations (BR) have been tightened regularly, causing increased focus on re-insulation and sealed constructions. But as we are now experiencing the consequences of the tightened requirements regarding problems of overheating in new and energy-retrofitted houses, it is urgent to assess the Danish Building Regulations’ influence on the thermal environments of Danish houses. This paper investigates the consequences of rising outdoor temperatures on the indoor temperatures of Danish detached houses providing state-of-the-art on the subject. Through studies of the Danish Building Regulations, the paper examines how we ended up with overheated houses in the first place. Furthermore, it discusses the influence of the Danish ‘Design Reference Year’ (DRY 2013) on indoor temperatures in the future. Finally, the paper points towards different solutions, which could decrease the risk of indoor overheating and improve the thermal indoor environment.