Whether on the transport or housing front, a number of cities have already implemented innovative solutions to tap into the benefits of density and reduce their carbon footprint. This section features four case studies from the UK and abroad to help cities tackle their own net zero challenge.
Case study 1: Climate Innovation District, Leeds
Situated on a former brownfield site on the banks of the River Aire, the Leeds Climate Innovation District is a good example of a new low-carbon residential development. It has around 520 homes that are built with insulated timber panels made in an on-site manufacturing plant, to reduce the emissions of each property during construction and when occupied. They need far less heating than traditional homes, as they require no gas central heating system. Electricity is provided by solar panels on the roof, and supplemented by 100 per cent renewable energy.
The location of the development encourages low-carbon lifestyles. Built at ‘gentle’ density levels (with three- or four-storey buildings), it is within walking or cycling distance from the centre of Leeds. Less than a seven-minute cycle to the station, it is near amenities such as schools and office space. The development features car-free streets, with only a few underground parking spaces provided at an extra cost. This is likely to reduce transport emissions generated by residents.
Researchers from the University of Leeds have designed a tool that assesses the active travel provision and potential of a range of new residential developments in the UK.41 It shows that, while most other developments are still very much car dependent, the highest bus use is within the Climate Innovation District. Around 39 per cent of commutes are made by walking, cycling or public transport (walking accounts for 37 per cent) and researchers estimate this could rise to 47 per cent (based on existing travel patterns and workplace locations).
Image source: Citu, OpenStreetMap
Case study 2: A model from abroad – Freiburg, Germany
Freiburg is a city in southern Germany that is home to just over 230,000 people. It has long attracted positive press for its sustainable development model.
In the 1970s, when local ‘green’ politics crystallised in opposition to the construction of a nuclear power station nearby,42 Freiburg pedestrianised its city centre and expanded local cycling and light rail networks.43 Throughout the 1980s and 1990s, the city pushed this sustainable agenda, as the development of local public transport infrastructure intensified and new housing and planning projects began.
Reducing dependence on cars and building on the benefits of density have been central to Freiburg’s approach. This was achieved through a combination of land-use policies restricting new development along public transport corridors on land immediately adjacent to built-up areas (preventing excessive sprawl) on the one hand, and interventionist public transport policies on the other. Whereas 39 per cent of all journeys completed by residents were in cars in 1982, cars account for only 21 per cent of such journeys today. Despite a booming local economy and growing population, average car mileage in the city fell by 7 per cent across all roads and 13 per cent on residential streets between 1990 and 2006, and per capita transport-related CO2 emissions concurrently fell by 13 per cent.44 The city is now known for its extensive public transport system – around 70 per cent of the population lives within 500m of a tram stop.
Central to Freiburg’s sustainable image is the Vauban neighbourhood, which was constructed in the late 1990s, three kilometres away from the centre of Freiburg and is home to around 5,500 people.45 Built on brownfield land using sustainable techniques (such as innovative passive heating, photovoltaics and wastewater management), the development is made of three- or four-storey buildings, achieving ‘gentle’ density levels.46 Car ownership is discouraged. Though access for pedestrians and cyclists is protected, roads are discontinuous and parking is limited. In Vauban, car ownership is further discouraged by low speed limits and parking arrangements that are both inconvenient and expensive.47 Consequently, the rate of car ownership is below that of Freiburg as a whole; only 48 per cent of Vauban residents, for example, have access to a car, and many of them rely on car-sharing networks.48 As a result, Vauban’s residents’ carbon footprint is much lower than elsewhere in the country: on average, residents emit 0.5 tonnes of CO2 annually – a figure far below the German average of 9.4 tonnes.49
Case study 3: District heating: using the benefits of density to decarbonise homes
Individual gas boilers are the most popular heating system in the UK today, but district heating schemes (sometimes called heat networks) are an alternative solution. Boilers are replaced by a centralised energy supply that redistributes heat to residential and commercial buildings through insulated pipes underground.
District heating is often seen as the most cost-effective way of cutting emissions from buildings (it is estimated to reduce primary energy demand in heating and cooling by 50 per cent). Economies of scale make it more efficient at generating heat, and it has the potential to switch to fully renewable energy sources.
It is particularly suited to dense urban environments, as it needs a certain level of demand to be economically viable. If the heat source is low carbon, district heating brings considerable benefits, as it effectively decarbonises multiple homes at once.
A number of UK cities, including Nottingham, Sheffield and Southampton, have already adopted schemes. London recently announced innovative plans for the Bunhill Heat and Power Network, providing heat for more than 1,300 homes using power from the London Underground.
Compared with other countries, the take-up of district heating is quite low in the UK. Only 2 per cent of homes are connected to a heat network, unlike in Denmark where it is more than 60 per cent. In Copenhagen, for instance, more than 95 per cent of heat is provided through low-carbon district energy networks, and it emits 40 per cent fewer carbon emissions than individual boilers.
If the UK is to achieve its climate target, take-up of these schemes will need to rise. The Climate Change Committee recently stated that a fifth of homes would need to be connected to low-carbon heat networks by 2050, alongside other options like heat pumps.