Words by Freija Carlstén and Emmelie Nilsson
Solutions to many of our urban problems can be found up on the roof, say Freija Carlstén and Emmelie Nilsson
Roofs are an increasingly valuable urban space
When you fly over a city, you see a lot of empty roofs that could be used more productively. Roofs offer one answer to many of the challenges that growing cities face: diminishing biodiversity, increased competition for land, greater demand for energy, and the effects of climate change such as higher temperatures, extreme rainfall and drought. This is something we need to deal with in the urban landscape, of which roofs constitute a great, yet overlooked, part.
The roofs of the future will be multifaceted
We need to deal with our roofscape holistically. We’ve been looking at three different ways to use roofs: green roofs, energy-producing roofs with solar panels, and roofs that could be used for social or commercial purposes, such as recreation or farming. Green roofs provide valuable green infrastructure in a city, to support biodiversity, help to regulate temperatures and attenuate heavier rainfall. Roofs used for socialising or recreation can add value to properties and generate income. Cities consume the most energy, so if we can generate it locally, there will be less pressure on power distribution systems.
We need to build a knowledge bank of roofs
WSP has already created a GIS-based tool, the Solkartan (sunmap), to show the potential electricity that could be generated for almost every roof in Stockholm. Now we’re planning to expand the tool to support multi-use roofs, adding data such as proximity to other green spaces or social areas, the age and construction of the building, the angle of the roof, local regulations. So you could click on a roof and see it has this much potential for green space, this much for energy generation, and that 25% of the area could be used for a meeting place.
Solar roofs can be green roofs (and cafes) too
Combining different functions increases the value of roofs further, which should interest most property developers. Solar panels work more efficiently on green roofs because the planting lowers the roof temperature, while the panels offer a more varied habitat for flora and fauna. Some species thrive under the shadow of the solar panels, while some prefer direct sunlight. Green roofs combined with social and commercial uses are good for recreational purposes, and also offer more attractive views, increasing property values and wellbeing. People are more likely to visit a roof that has greenery on it than one that doesn’t.
Cities need to create a vision for their whole roofscape
Coordinating these functions across a city optimises their potential. For that, you need to have the whole picture. You might see that one area of buildings is dividing two nature reserves, so you could install green roofs with a high ecological value to create a corridor for pollinators. If we did this analysis at a regional or city level, municipalities could then set a strategy for a whole roof landscape and use it to meet their sustainability goals.
Freija Carlstén is a landscape architect and Emmelie Nilsson is an environmental strategist at WSP in Stockholm