CS-N0W delivers strategic studies for government on climate impacts to housing and how to prepare the UK housing stock
Home equity is many people’s most valuable asset. Hazards such as fires, floods, subsidence and storm surge that threaten that asset, and its insurability, can represent a significant climate risk. Homes and urban design that are poorly adapted for our changing climate can have significant negative health impacts for inhabitants, particularly for more vulnerable population subgroups.
The Climate Services for a Net Zero Resilient World (CS-N0W) programme, led by Ricardo, delivered a series of studies on behalf of the UK government to improve understanding of how climate change is likely to impact UK housing and how to adapt the housing stock.
First, the Tyndall Centre for Climate Change Research aimed to answer the question: What climate impacts to the UK would be avoided by limiting global warming to 1.5 °C compared to higher levels of warming? The study modelled and mapped projected indicators of climate-related risks for the UK at global warming levels of 1.5, 2, 3 and 4 °C above pre-industrial levels for flood and overheating related to housing.
The risk of flooding is already high in the UK. Approximately 1.9 million people currently live in areas at significant risk from surface water, fluvial and/or coastal flooding. The Tyndall study found that all types of flooding are projected to increase with climate change. In a scenario where global warming reaches 3 °C by the 2050s before stabilising out to the 2080s, expected annual damages from flooding to residential properties are projected to increase almost sixfold, from ~£500m to £2,800m, in the absence of adaptation. Estuaries and coasts around the UK are expected to experience some of the largest increases in damage to property.
More action is also needed to tackle the current and future risk of overheating in homes. According to the Climate Change Committee, people in the UK spend on average 90% of each day indoors, and around 20% of homes already overheat even outside of heatwave events. The Tyndall study estimated that global warming of 3 °C could increase heat-related deaths tenfold in England in the absence of adaptation. The Heat Adaptation and Risk Model projected 6,376 additional average annual heat-related deaths in this scenario by 2080 compared to 678 annual deaths from 1980 to 2000.
How these impacts will play out depends largely on whether and how we adapt our housing stock, neighbourhoods, towns and cities. Buildings that incorporate passive cooling (well designed ventilation strategies, external shutters, etc.) and/or active cooling (e.g. fans or air conditioning) are less prone to overheating. Green infrastructure, such as urban trees and green roofs and walls, can potentially lower local temperatures.
The Institute for Environmental Design and Engineering at University College London (UCL) conducted a CS-N0W study that assessed future heating and cooling needs of the UK housing stock. It modelled the impact of different climate scenarios on residential thermal comfort across the UK for a range of dwelling archetypes and occupants. The study found that by the 2030s, without any changes to the building stock, the majority of UK household types would be prone to nighttime overheating. Bungalows and other detached properties were found to be cooler on average, whereas flats and mid-terrace houses were warmer and spent more hours above the indoor overheating threshold. The team recommended that near term interventions should prioritise passive cooling strategies and target the dwelling archetypes most prone to overheating.
The study found that four population subgroups are particularly vulnerable to indoor overheating – infants, older people, ethnic minorities and low-income individuals. These subgroups are more likely to be susceptible to negative heat impacts due to their limited ability to adapt to or cope with heat, and underlying health conditions, and/or potentially more exposed to overheating due to the location and type of buildings they typically occupy.
Lastly, the study worked with key stakeholders to identify low-cost, low-carbon, ‘win-win’ measures that could be adopted to minimise adverse climate impacts on the thermal performance of the UK housing stock. The most effective retrofit for reducing overheating risk and associated cooling demand was external shutters. However, due to the diverse characteristics of the housing stock and households, the study identified no “one-size-fits-all” solution.
A follow-on CS-N0W project by the UCL Building Stock Lab produced a data visualisation tool that is hosted on the website of the Department for Environment, Food and Rural Affairs (see below). The tool provides users with an interactive map that layers the modelled estimates of future indoor overheating across England and Wales for a range of climate change projections. It allows users to compare the impacts of packages of retrofits, including insulation and internal and external shading, for reducing emissions and adapting to higher temperatures in different building archetypes. The data visualisation tool is an invaluable starting point for local councils and other stakeholders delivering adaptation interventions.
Figure 1: Overheating in Buildings data visualisation tool on Department for Environment, Food & Rural Affairs website
Source: https://environment.data.gov.uk/over-heating/
A further CS-N0W case study was conducted on heat vulnerability and options to adapt urban buildings in Manchester. The study, delivered jointly by Ricardo, UCL and the University of Manchester, combined modelling assessments of buildings prone to overheating and potential adaptations with socio-technical analysis on barriers that may hinder their implementation. It found that vulnerable households often have restricted capacity to adapt due to financial limitations, deterrents to window opening (noise, air pollution or security concerns), or landlord restrictions on retrofits in rental properties. These findings demonstrate the importance of mixed method approaches to vulnerability assessments and adaptation planning.
It is also critical that adaptation planning for the building stock be considered alongside decarbonisation strategies to prevent adverse consequences, such as exacerbating climate risks or increasing greenhouse gas emissions. A CS-N0W study led by UCL modelled the health impacts of net zero housing measures using the National Building Model. It found that home retrofits to improve energy efficiency could lead to a small increase in summertime indoor temperatures (~0.2-0.3°C). However, this increase can be more than offset by overheating adaptations, including external shutters, urban greening, window shading or coating with solar control glazing and painting walls and roofs to modify their solar absorptance.
Active cooling measures, such as air conditioning, may lead to higher greenhouse gas emissions if powered by carbon-intensive electricity, highlighting the need for the UK to achieve its ambitious decarbonisation target for the electricity system. Under the CS-N0W programme, Ricardo undertook the first stocktake of cooling emissions in the UK. Active cooling technologies are currently sparsely used in UK homes, but more prevalent in businesses. The data from this stocktake will enable policy interventions to limit emissions growth as cooling technologies become more common.
In contrast, passive cooling measures can both address overheating in buildings and reduce energy demand, hence supporting mitigation. For this reason, green cover, natural ventilation and better shading were among the top low-regret options identified by a Ricardo-led CS-N0W study on co-benefits and trade-offs of UK climate actions.
The Climate Change Committee’s Third Independent Assessment of UK Climate Risk called for more strategic research to better understand the impacts of climate change on UK housing and how to prepare the housing stock. The wide variety of studies conducted by the CS-N0W programme will provide an invaluable evidence base for the Fourth Climate Change Risk Assessment in 2026.
