Gary Walpole explains how roofs could hold the solution to climate change adaptation
What do you picture when you think of a roof? Probably a pitched roof with tiles, a felted flat roof, or even a metal warehouse roof. A roof is probably the last thing you would imagine when considering climate change adaptation – but recent research from the University of Southampton and the National Federation of Roofing Contractors makes the case that the way we build, maintain and retrofit our roofs may actually help the UK to mitigate some of the impacts of climate change on the built environment.
A changing climate
The research, Future (P)roof – Building resilience of roofing technologies in a changing climate, was based on the most recent UK climate change modelling, UKCP18, published in July 2021. This forecasts that the UK is expected to have not only warmer and wetter winters, but also higher temperatures in other seasons, including more heatwaves and higher summer irradiance due to clearer and drier skies.
There is expected to be an increase in predicted peak rainfall (90th percentile) in a 24-hour period – so more high-intensity rainfall events. Future (P)roof took this modelling and applied it to a range of built forms in 15 cities across the UK. It identified that the major risks to the built environment from climate change would be overheating and flooding.
Overheating is already a problem in the UK during the summer, and is only set to intensify. In Islington, London, temperatures are expected to rise by 3.3°C by the 2080s, and its daily maximum temperature is expected to increase from 22.2°C to 27.9°C during the same period. Loft conversions are particularly exposed, and this could be an issue for southern UK cities as early as 2030.
In addition, river, groundwater and surface flooding due to extreme weather events are regarded as medium risks today by the government’s Independent Assessment of UK Climate Risk in terms of building damage and productivity loss.
Future (P)roof explained how roofing technology could mitigate both risks. Overheating may be addressed by using ‘cool roof’ technology, designed to reflect more sunlight and absorb less heat. This can be achieved using highly reflective paint, tiles or waterproof coverings.
Green and blue roof technology could be used in conjunction to tackle flooding and overheating. Green roofs cover a conventional roof with a waterproof layer, a growing medium and vegetation. As well as reducing climate change impacts on the building itself, green roofs help mitigate the impact on the surrounding environment by reducing the urban heat island effect. They also act as an important source of biodiversity in urban areas, as well as a social amenity if they are accessible.
Blue roofs are sustainable urban drainage systems that attenuate and manage stormwater over a 24-hour period, rather than allowing it to rapidly flow down to ground level. They offer greater environmental performance when designed beneath a green roof, which acts as a ‘sponge’ for rainwater.
In terms of energy resilience, the typical pitched roof can be retrofitted to include built-in solar PV, generating electricity for the property, as well as enhanced roof insulation, which reduces heat demand (in a typical home, 25% of heat is lost through the roof). Commercial roofs are also an ideal location for solar, and research has shown that rooftop solar installed at scale in a city such as Southampton could provide 25% of that city’s electricity demand.
Breaking down barriers
The case for using our roofs to adapt to climate change is clear, so why are we not urgently retrofitting them at scale? Unfortunately, many barriers remain – from planning policy and a lack of green skills in the industry, to financial barriers among households and businesses. Future (P)roof makes recommendations to industry, local and central government on how to break down these barriers.
Next time you look up, think about the potential our roofscape holds to reduce the impact of climate change and build a more sustainable energy system. We need to make it a reality.
Gary Walpole is a safety, health and environmental officer at the National Federation of Roofing Contractors.