04How a changing approach to development can help achieve net zero

The UK needs to change its approach to planning and development to achieve net zero. This section sets out modelling on the impact that this change of approach could have on net zero, in conjunction with the take-up of electric vehicles (EVs) the retrofitting of existing houses and the building of more energy efficient new homes.

Modelling the impact of a modal shift on transport emissions

Cutting transport-related emissions often relies on projections showing a significant uptake of EVs and Battery Electric Vehicles (BEVs), in particular. But relying on a shift to cleaner vehicles must not be considered as the only solution (Box 6). Wider benefits can be reaped through modal shift, with an increase in public transport and active travel usage.

Figure 11 is based on modelling by Centre for Cities. It focuses on emissions from commuter journeys and estimates the potential reduction in carbon emissions if cars accounted for only a third of these journeys (as they currently do in London), against more than 60 per cent today.24 It uses modal share data, population projections for all cities, average distance to work and estimates of car emissions per kilometre/passenger by 2035.25

On the last metric, three scenarios have been considered:

  1. No change, where there is no significant uptake in the number and share of EVs and BEVs by 2035.
  2. An optimistic scenario where, in 2035, BEVs account for two-thirds of the fleet (which is in line with the Government’s expected phase out of petrol and diesel cars by 2030).
  3. A ‘middle ground’ scenario where, by 2035, BEVs account for a third of the fleet.

Figure 11 shows a worst-case scenario where neither the composition of the fleet nor modal share changes. In this case, transport emissions are expected to rise as a result of projected population growth, and subsequent increases in traffic levels.

It also shows the extent to which a change in modal share can get cities closer to net zero emissions in the transport sector, regardless of the composition of the fleet. Even in a scenario where there is no significant uptake of EVs, the impact of a change in modal share is clear: car-related emissions would more than halve.

In the best-case scenario, where EVs make up two-thirds of the fleet and cars account for only a third of all journeys, emissions from these journeys would be cut by 87 per cent compared with today’s levels. While gains from modal shift are reduced, they still play an important role.

Figure 11: Emissions could halve by 2035 if cars only account for a third of all journeys

Source: DfT, 2020; Census, 2011. Centre for Cities’ own calculations.

The impact of each scenario varies from place to place. In the absence of change, cities and large towns like Coventry or Bristol would see their emissions go up by 20 per cent and 12 per cent respectively, mostly driven by population growth. And, conversely, modal shift would have the biggest impact in cities like Aldershot, Blackburn or Burnley. Emissions in these cities are 60 per cent higher today than they would be if car usage was at London levels.

Box 6: EVs are an important part of the solution, but they should not be seen as the only way to achieve a greener future

The Government recently announced that the sales ban for petrol and diesel engines, initially planned for 2040, would be brought forward to 2030. This is welcome news, as it is expected to cut CO2 and nitrogen dioxide (NO2) emissions, especially given the underlying assumption that there will be significant uptake of zero emission vehicles in the run up to 2030. While a transition to EVs would have a number of benefits, they are not the panacea, especially in cities.

First, while they have no exhausts, they still emit harmful fine particulate matter (PM2.5) through brakes and tyre wear, and this is the cause of more than 14,000 deaths a year in cities alone.26

Second, EVs would put a strong burden on local grids, and a lot of electricity cables and power stations would be required.

Third, they still take up a considerable – and valuable – amount of space (the same as for a petrol or diesel car). Data for London shows the average car is parked at least 95 per cent of the time, and 43 per cent are parked on the street.27 A transition to EVs would not free up space for public transport and active travel, bus lanes or segregated cycling infrastructure.

Cities need fewer cars, not just cleaner cars. In the densest urban areas, investment must be targeted towards disincentivising driving. The focus for EVs must be on residual journeys outside dense urban areas where there are no (or few) alternatives.

Box 7: Is remote working the solution to cutting carbon emissions?

It has often been suggested that working from home provides a solution, both in terms of improving air quality and reducing carbon emissions.28 In particular, this has been argued during the Covid-19 pandemic, which triggered a surge in remote-working patterns.

While it might reduce transport emissions from commutable journeys and, in some cases, cut overall emissions, it is important to nuance this argument. Commutes only represent 14 per cent of car trips, so are not the largest contributor to emissions. Density still matters because it determines the average distance of other journeys (such as grocery shopping or leisure), and therefore the likelihood of people walking or using public transport.

This is particularly true where a household moves further away from a city centre to a less dense area because they do not need to go to the office every day. Provided they did not use public transport for their commute, they might save carbon on that journey. However, they may end up using a car more for other purposes. As a result, their total carbon footprint would either remain unchanged or increase, especially if they moved to a larger home that uses more energy.

Such a shift from cars to public transport can be achieved through a number of policy interventions,  such as disincentivising car usage by making driving more expensive or investing in public transport infrastructure. But, to be the most impactful and reach a potential transport emission cuts of up to 87 per cent as shown above, many of these policies will need to be underpinned by changes in density. An associated increase in demand that arises in denser environments would, for instance, support the development of new public transport routes or make existing ones more viable, and facilitate the transition away from cars.

This has important implications in terms of housebuilding policies and spatial planning more generally. If the UK is to increase its provision of homes by 2.3 million in the next decade, then it is crucial to build them in the right locations.29 Densifying existing built-up areas will reduce the carbon footprint of both new and existing residents, especially in large cities like Manchester, Birmingham, Leeds or Sheffield, which are currently way below London’s density levels. If 10 per cent of Manchester’s built-up area matched the levels of west London’s densest neighbourhood, it could accommodate an extra 963,000 people, resulting in a 40 per cent increase in density.

This does not necessarily mean building skyscrapers, as examples from London show (Box 8). ‘Gentle’ density can be achieved, for instance, by constructing four- to six-storey buildings on empty brownfield land within city boundaries.

While in many of these cities there is potential for infill development in city centres, it should not be only the immediate city centre that accommodates extra density. As places of production and consumption, they need to balance residential and commercial space, and inner city, well-connected suburban areas will need to densify.

Box 8: Increase in density and car use – examples from London

In recent years, many areas in London have experienced an increase in density levels well above 20 and even 50 per cent. Some places in Stratford, in the London Borough of Newham, are often used as examples of mid- to high-density living. Census data for 2001 and 2011, at the lower super output area level, shows the neighbourhood by Stratford station saw density increase significantly when the area was chosen to host the London 2012 Olympics. Over that decade, its population nearly doubled. Public transport use rose significantly, from 58 per cent in 2001 to 79 per cent in 2011. This was driven by an increase in density, and investments in public transport links (such as Stratford International station and the expansion of the Docklands Light Railway), with the latter underpinned, in part, by the former. The location of jobs matter too: between these two dates, the proportion of people commuting from Newham to central London has increased by four percentage points.

Croydon is another example. In the neighbourhood that surrounds Wandle Park, the population nearly doubled between 2001 and 2011 too. And, given the area just a few hundred metres south did not experience any significant increase, the gap in public transport use is striking. In 2001 both areas had similar modal shares, with around 36 per cent of residents using public transport. However, it rose by 20 percentage points in the former, but barely changed in the latter.

In Stratford and Croydon, higher density levels were achieved through the construction of mid-to-high rise buildings (see Figure 12).

Figure 12: Typical new development in Stratford (left) and Croydon (right)

Source: Google Maps, 2021

Further emissions reductions could be achieved if cities retrofit their housing stock

The Climate Change Committee has made it clear that the UK is unlikely to meet its targets for emissions reductions without retrofitting large sections of the existing housing stock (Box 9).30 This is because the large majority of the buildings that will be there in 2050 have already been built, hence the importance of focusing on existing dwellings.

Energy inefficient housing is disproportionately located in urban areas. Of the total 11.2 million homes that are currently below EPC band C in England and Wales, 6.3 million are located in cities and large towns – some 56 per cent of the total.31

Averaged across all cities, only 38 per cent of housing is rated A to C (the three most efficient bands). This is largely down to the nature of the stock, which tends to be quite old and inefficient and has been upgraded at a very slow pace in recent years. However, the age of the properties is not the only factor: in 2019, less than 1.5 per cent of all new homes were rated A, which reflects a lack of ambitious regulations in terms of building performance standards.32

Box 9: Retrofitting the housing stock – the scale of the challenge

Shifting to low-carbon alternatives will be key to decarbonising the domestic sector (e.g. through electrification), but improving the energy efficiency of homes is likely to play an important role, too. With more than a third of UK housing stock built before the Second World War, homes have poor energy efficiency compared with homes in other countries.

The Clean Growth Strategy, published in 2017, seeks to address this problem with an objective to upgrade “as many homes as possible” to EPC band C by 2035. This would include cavity and loft insulation, as well as double glazing or solid wall insulation. Upgrading homes is expected to significantly contribute to carbon emission reductions (Table 3). However, the benefits go beyond this, as energy-inefficient homes tend to be more expensive to run. On average, a property graded F is five times more expensive than one graded A or B. Even the most common rating (band D) is twice as costly as band A or B.33

Table 3: The least energy efficient dwellings emit much more carbon
Average carbon emissions for each EPC grade

EPC grade Average CO2 emission per sqm (t) Average cost per year (£)
A 0.3 396
B 1.7 396
C 3.2 643
D 4.7 921
E 6.5 1,391
F 8.7 2,008
G 12 2,998

Source: EPC Domestic Register, 2019.

There is a geography to this issue. Of the 10 cities and large towns most in need of retrofitting, seven are in the North or the Midlands (see Figure 13). In Burnley, for instance, 80 per cent of the housing stock is below EPC band C. In larger cities, like Birmingham, the share is slightly lower but, in total, half a million properties would need retrofitting. In London it is more than 1.7 million.

Figure 13: In some cities, more than 70 per cent of the housing stock needs retrofitting

Source: EPC Domestic Register, 2019.

Modelling that takes into account the current stock of homes that need upgrading, average emissions from each EPC band, household projections and an ‘ideal’ scenario in which all new builds are rated B from 2022, suggests that retrofitting would help cut domestic emissions by nearly 40 per cent in places like Burnley, Luton and Bradford (Table 4). Even in cities and large towns with a low proportion of homes in need of retrofitting, such as Telford, Crawley and Swindon, domestic emissions could be reduced by nearly 25 per cent compared with current levels.

Table 4: Retrofitting the housing stock could save up to 40 per cent in carbon emissions

City Potential reduction in domestic emissions – top 10 City Potential reduction in domestic emissions – bottom 10
Burnley 39% Coventry 26%
Luton 38% Wakefield 26%
Bradford 38% Slough 26%
Swansea 37% Exeter 26%
Blackburn 36% Peterborough 25%
Oxford 35% Basildon 25%
Blackpool 35% Milton Keynes 24%
Birkenhead 35% Swindon 22%
Derby 35% Crawley 22%
Ipswich 34% Telford 21%

Source: EPC Domestic Register, 2019. Centre for Cities’ own calculations. Note: this is a scenario where all new builds until 2035 are in EPC band B.

Modelling the impact of retrofitting on domestic emissions

Further cuts in domestic emissions can be achieved if the right types of homes are built in the right locations. This reflects the benefits associated with building in a more compact way, as blocks of flats tend to have a much lower carbon footprint than houses, particularly those that are detached.

Centre for Cities’ modelling shows that if density levels increased by 20 per cent everywhere, domestic emissions would fall by 5.7 per cent on average.34 35 This reduction in emissions would be equivalent to more than twice the size of Newcastle’s current domestic emissions.


  • 24 Averaged across all cities, 63 per cent of people commute by car – this ranges from 34 per cent in cities like London and Cambridge to 76 per cent in Telford and Swansea. In the latter group of cities, average distances to work are also longer (Source: Census, 2011). The patterns are unlikely to have changed drastically in recent years, according to bus ridership data and traffic levels in cities.
  • 25 In order to estimate the potential cuts in emissions from all car-journeys, the values have been extrapolated based on the share that commutes and business trips represent out of all car journeys, around 35 per cent (DfT, 2020).
  • 26 Enenkel, K. and Quinio, V., 2019, Cities Outlook, London: Centre for Cities.
  • 27 Centre for London (2020), Reclaim the kerb, The future of parking and kerb management.
  • 28 See for instance RTPI (2021), Net Zero Transport, The role of spatial planning and place-based solutions. See also www.globalactionplan.org.uk/news/remote-working-vital-post-lockdown-to-keep-air-pollution-lowwith-87of-workers-wanting-to-continue-to-do-so
  • 29 Barton C. and Garton-Grimwood G. (2018) Housing targets: Can we predict future need? House of Commons Library Analysis, 2 October 2018.
  • 30 Climate Change Committee (2019). UK housing fit for the future.
  • 31 Despite being the best available data on housing energy-efficiency, EPCs are an imperfect measure. As not all properties have an EPC, this is likely to be an under-estimate of the total number of dwellings that need retrofitting.
  • 32 EPC Domestic Register, 2019.
  • 33 The problem is that the cost of investment for retrofit measures is often too high to be offset by savings on energy bills. This will need to be addressed.
  • 34 This is echoed in a number of US-based research, where benefits of density are even more pronounced. For instance, Glaeser shows: “The average single-family detached home consumes 88 per cent more electricity than the average apartment in a five-or- more-units building. The average suburban household consumes 27 per cent less electricity than the average urban household”. The difference in scale may be explained by the fact that many UK dense, central urban areas have older, poorly-efficient housing which tends to distort the impact of density. See Glaeser, E., Kahn, M. (2003). Sprawl and urban growth. National Bureau of Economic Research.
  • 35 The model used is the following: Domestic CO2 = BUA density + dwelling area per capita + % of dwellings below C