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

Abstract

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.

Understanding and mitigating overheating and indoor PM2.5 risks using coupled temperature and indoor air quality models

“…14 Solid wall insulation was found to be particularly dangerous for increasing the overheating risk, consistent with previous studies, 8,27 whilst airtightening was found to be another significant contributor to overheating risk. In addition, this paper demonstrates the risks to occupants from retrofits where additional compensatory ventilation is provided.…”

“…A large monitoring study of UK dwellings found that flats and modern homes have an increased risk of overheating, 6 similar to the results predicted by modelling studies. 7 Building characteristics such as built form and building fabric design, air change rate, the storey level of flats in multifamily buildings and orientation [7][8][9] ; local environment of the building (including shading, microclimate and urban heat island) 7,10,11 and occupant behaviour 12 may all influence the risk of overheating. The geographical location of dwellings within the UK may also have an impact on both absolute overheating risk and the relative risk of overheating amongst different dwelling types.…”

Overheating in buildings: lessons from research

“…Furthermore, extensions, conservatories, new window systems and other adaptations all conspire to reduce the prospects for adequate ventilation and increase the risk of summertime overheating. Whilst the potential for exacerbating overheating risk is now recognized (DECC, 2015;Porritt, Cropper, Shao, & Goodier, 2013), the matter is paid little attention in practice.…”

Retrofitting Precincts for Heatwave Resilience: Challenges and Barriers in Australian Context

“…Comprehensive studies on the assessment of different retrofitting techniques, such as a retrofitting toolkit from UK [69] are few in number. The efficiency of mitigation techniques is rarely compared across different climates, despite the importance of climate specific design [23].…”