Low energy housing retrofit in North England: Overheating risks and possible mitigation strategies

In the drive to reduce space-heating demand and associated CO2 emissions as well as tackle fuel poverty, dwelling overheating and summer-time occupant thermal discomfort might be the unintended consequences of low-energy building retrofits. This paper presents the findings of a steady-state modelled low energy retrofit dwelling in northern England and its potential current and future climate overheating risks using UK Climate Projections 2009 (UKCP09) scenarios (2050 and 2080 High Emission Scenarios). Predictive findings highlight that retrofitting to low energy standards increases overheating risk over time, unless passive prevention measures are included in the retrofit design. In addition, the steady-state nature of the model might not fully capture the occupants’ exposure to actual future overheating risks. Among the most effective individual passive overheating mitigation strategies are temporary internal shading, permanent external shading, and night-time ventilation. Most effective is a combination of these adaptation measures, so that predictive overheating is minimised in a future changing climate, reducing the uptake of active cooling in retrofitted dwellings. Practical applications: Much research focuses on building overheating risks in the warmer South-east of England. However, this paper highlights how dwelling retrofit in north England (Sheffield) also can lead to increased dwelling overheating risk, unless passive design measures are included in the retrofit design. Among the most effective individual passive overheating mitigation strategies are solar shading devices and increased night-time ventilation, though ideally different measures are combined. Using future climate scenarios highlights that retrofits designed today might not be able to provide occupant thermal comfort in a future warming world.