Heat wave adaptations for UK dwellings and development of a retrofit toolkit

Purpose – Dwelling retrofit strategies generally concentrate on measures to reduce energy use and carbon emissions. However, climate change projections predict increases in both the frequency and severity of extreme weather events, including heat waves. It is predicted that by the 2040s severe heat waves similar to the European one in August 2003 may be expected to occur every year. Future guidance therefore needs to combine mitigation with adaptation in order to provide safe and comfortable dwellings, whilst also reducing heating energy use, within the available retrofit budget. The paper aims to discuss these issues. Design/methodology/approach – The research presented here used dynamic thermal simulation (EnergyPlus) to model a range of passive interventions on selected dwelling types to predict the effect on both dwelling overheating during a heat wave and annual space heating energy use. The interventions include modifications and additions to solar control, insulation and ventilation. Findings – Results demonstrate the effectiveness of interventions that reduce solar heat gains, with external shutters fitted to windows being the most effective single intervention in many cases. Solar reflective coatings also reduce overheating but lead to increased winter heating energy use, whilst wall insulation reduces heating energy use but can, in some cases, lead to increased overheating. The choice of wall insulation type is shown to be very important, with external insulation consistently performing better than internal for overheating reduction. The modelling further demonstrates that combined interventions can significantly reduce or in many cases eliminate overheating. Overheating exposure was found to vary significantly (up to a factor of ten times) between dwelling types. It can be significantly greater for residents who have to stay at home during the daytime, such as the elderly or infirm, and different interventions are sometimes more suitable in these cases. Originality/value – An innovative modelling methodology integrating overheating reduction, heating energy use and intervention cost has been developed and implemented for adapting UK dwellings to future heat waves. Other innovations include an automated approach for large volumes of simulations (over 180,000); a unique graphical interpretation method for presenting single and combined intervention results; and a user-friendly, interactive retrofit toolkit, which is available online for public access and free of charge.