London’s Mayor Sadiq Khan has brought the city’s deadline to become carbon neutral forward from 2050 to 2030.  

This is a two-decade leap from the UK government’s legal commitment – to reach this target by 2050 – but Khan says he will implement his 10-point plan to achieve it if elected for a second term in the mayoral election on 7 May.

“Some say that a 2030 target isn’t achievable but I say we can’t afford not to try,” he said, adding that the task would be made much easier if the UK government were to step up its own climate ambition and devolve more powers to cities.

According to The Association for Decentralised Energy, London has to retrofit 2.9 million homes just to meet the target it set itself in its 2011, although it says “significant upgrades to the efficiency of London’s buildings have been made in recent years”.

Despite this it is presently falling behind that target. It’s not easy, as 60 per cent of its homes have solid walls, which are more expensive and difficult to insulate.

London’s zero carbon scenario is therefore dependent upon the decarbonisation of the electricity and gas grids, a dependency enshrined in the government’s proposed new Future Homes Standard  for new homes and criticised by green lobby groups – see below.

The city faces a challenge in tackling emissions from waste too, since its 33 boroughs have different recycling schemes and the mayor has no statutory responsibility for that area.

On transport, the bus fleet is already scheduled to be completely zero emissions by 2037 – this target must now be made more ambitious. Cycling is encouraged in London, but London will face challenges with reducing the impact of air travel – the hardest component of transport emissions for a city to tackle.

Supported by C40’s Climate Action Planning Framework London’s 1.5o Climate Action Plan relies heavily on Arup’s Building Energy Efficiency model and the use of increasing electrification, decarbonisation of gas, decentralisation of energy and patchwork solutions; and a review by Mott McDonald of existing activity on climate adaptation to avoid the impacts of increasingly hot, dry summers and unpredictable weather.

Net Zero London

To support the mayor’s target the London Energy Transformation Initiative (LETI) has launched a Climate Emergency Design Guide and an Embodied Carbon Primer, which set out the approach, targets and benchmarks that developments in the UK need to achieve to reach Net Zero in operation.

According to the Mayor’s plan, by 2030 all new buildings will need to operate at Net Zero, which means that by 2025 all buildings must be designed to reach this target, allowing them five years to sense check, refine and validate this approach.

LETI is a network of over 1000 built environment professionals that are working together to put London on the path to a zero carbon future. It is made up of developers, engineers, housing associations, architects, planners, academics, sustainability professionals, contractors and facilities managers.

They have developed the following Net Zero Operational Carbon building features in collaboration with the UK Green Buildings Council and Better Buildings Partnership. All of their members have pledged to adopt it. Net Zero buildings must be:

  1. Low energy use, with metered use equal to or less than 35 kWh a square metre annually (GIA) for residential buildings
  2. For non-domestic buildings a minimum Display Energy Certificate B (40) rating and/or 65 kWh a sq m annually for schools, 70 kWh a sq m annually, or 55 kWh a sq m annually for commercial offices
  3. Space heating demand less than 15 kWh a sq m annually for all building types
  4. Annual energy use and renewable energy generation on-site reported and independently verified in-use each year for the first five years
  5. Embodied carbon should be assessed, reduced and verified post-construction
  6. No use of fossil fuels, and the average annual carbon content of the heat supplied (gCO/kWh) needs to be reported.
  7. On-site renewable electricity to be maximised.
  8. Energy demand response and storage measures to be incorporated and the building’s annual peak energy demand should be reported.
  9. A carbon balance calculation (on an annual basis) should be undertaken and it should be demonstrated that the building achieves a net zero carbon balance.
  10. Any energy use not met by on-site renewables should be met by an investment into additional renewable energy capacity off-site, or a minimum 15 year renewable energy power purchase agreement (PPA). A green tariff is not considered robust enough and does not provide “additional” renewables.

Future Homes Standard

The above all goes further than current proposals for changes to UK-wide official Building Regulations aimed at tackling the climate emergency, featured in the Future Homes Standard consultation which expired a week ago, and which could take effect this year.

The building regulations proposals have been slammed by the Architects Climate Action Network and LETI, whose initiator Clara Bagenal George called them “extremely worrying” in the context of the climate emergency, views echoed by the UK Green Building Council.

They describe them as not fit for purpose to put the construction sector on the right trajectory to tackle the climate crisis, because they would “disguise poor fabric efficiency” through over-reliance on a decarbonised grid to achieve the target. They say that if designers are encouraged to rely on the decarbonisation of the electricity grid to become low carbon they are likely to be negligent about the energy efficiency of their buildings.

The architects want to see the Future Homes Standard prioritise “fabric energy efficiency”, which would also reduce energy bills for occupiers. They also want more emphasis on enforcement of the energy aspect of building regulations, which is currently poor, and for the regulations to cover the whole-life carbon emissions of buildings.

Furthermore, they want the energy use of all new homes designed in 2025 to be net zero; and local authorities to be at liberty to set higher local standards than those imposed by Westminster should they wish.

London already has the lowest carbon emissions per person in the UK, mostly due to high population density, extensive public transport and a comparative lack of heavy industry. However, much carbon is imported in goods, materials and services – and this would also need tackling to meet the mayor’s aims.

David Thorpe is author of the books The One Planet Life and the new One Planet Cities. He also runs on line courses such as Post-Graduate Certificate in One Planet Governance. He is based in the UK.

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  1. Solid masonry walls: injection waterproofing/ dpc into the masonry. Waterproof external paint systems. Special codes for heritage buildings to install 100 % renewable energy systems instead of reducing some of the energy intake. STOP building masonry walls without an insulated cavity. Heritage Smokestacks: put a lid on them, to open in summer and close in winter: use them as natural ventilators.

    I’m with the mayor on this- get to it you whinging architects.

  2. There are huge problems with insulating solid wall buildings. Best is an exterior insulated envelope, but that clashes with heritage listing and street character in many areas, and things like parapet walls and chimney stacks are difficult elements (that must be retained for heritage reasons).
    Interior insulation solves the heritage problem – except in buildings with listed interiors – but creates big problems with interstitial condensation unless it’s done perfectly, which it won’t be. Elements like timber floor joists sitting in pockets in exterior walls – and thus crossing the insulation layer – are really problematic. Bringing old, draughty Georgian and Victorian terraces up to modern airtightness standards is only likely to exacerbate the interstitial condensation issues.
    Workmanship is a key issue, and a key problem, in domestic construction, especially as many older buildings are subdivided into separate apartments, with separate ownerships, many as leaseholds, many let out as buy-to-let or short-term rentals… if you can think of a problem, it exists, in thinking of housing upgrades for sustainability.
    The Building Research Establishment (BRE) at Watford has done research on this in the last few years.