The London Energy Transformation Initiative (LETI) is a network of over 1000 built environment professionals that are working together to put the UK on the path to a zero carbon future. The voluntary group is made up of developers, engineers, housing associations, architects, planners, academics, sustainability professionals, contractors and facilities managers, with support and input provided by the GLA and London boroughs and other organisations, Elementa Consulting have initiated and coordinated LETI as they were frustrated that the current energy policy in London wasn’t driving design solutions that encouraged long term carbon emissions reduction.


LETI was established to work collaboratively to put together evidence-based recommendations for two pieces of policy – the new London Environment Strategy and the rewrite of the London Plan. Since then, our more recent Part L Campaign considered UK policy and we have worked to develop consensus within the industry on a definition for Net Zero Operational Carbon. Earlier this year, LETI launched the Climate Emergency Design Guide, which outlines requirements of new buildings to ensure our climate change targets are met.


Mission Statement

The London Energy Transformation Initiative has been established to support the transition of the capital’s built environment to net zero carbon, providing guidance that can be applied to the rest to the UK. We do this by:


→  engaging with stakeholders to develop a robust and rapid energy reduction approach, producing effective solutions to the energy trilemma of security, sustainability, and affordability

→  working with authorities to create practicable policy alterations to ensure the regulatory system is fit for purpose, placing verified performance at its core

→  encouraging and enabling collaboration between built environment professionals

→  providing technical advice to support exemplar developments, enabling pioneers who aspire to go beyond the current regulatory frameworks


1. LETI is focusing on zero carbon as the outcome, but we recognise that reducing energy demand in the first instance is key to achieving a net zero carbon city.


2. The built environment focuses on buildings, but taking a holistic view incorporating the wider infrastructure, from local transport links to the national energy grids, is essential to reduce carbon emissions.

What LETI has achieved so far

In 2017 and 2018 LETI's focus was to influence energy policy in London including the draft London Plan and the London Environment Strategy. Many of the recommendations that LETI put forward to the GLA have been included in emerging London policy and Energy Assessment Guidance:


Energy use disclosure: A Be Seen stage has been added to the energy hierarchy - this cements monitoring, verifying and reporting in the London plan.


Carbon factors: The draft London Plan recognises that Building Regulations use outdated carbon emission factors and that this will continue to cause uncertainty until they are updated by Government. The GLA Energy Assessment guidance recommends that SAP10 carbon factors (e.g. 233gCO2/kWh for electricity) are used from January 2019.


Whole life-cycle carbon: Referable schemes are to calculate whole life-cycle carbon emissions through a nationally recognised Whole Life-Cycle Carbon Assessment and demonstrate actions taken to reduce life-cycle carbon.

Enhanced fabric and systems: Requirement that a 10% reduction in carbon emissions for residential and 15% reduction for non-residential development are achieved using an efficient building fabric and systems.  (This does not include efficiency improvements of heating systems).


Increased transparency of design: Reporting on total energy demand (heating, hot water, cooling, lighting, auxiliary, unregulated electricity, unregulated gas in MWh/yr) and glazing ratio. FEES to be reported for residential.


Overheating: CIBSE TM52 or TM59 criteria is met using the DSY1 (2020’s 50th percentile) weather file and that sensitivity analyses is carried out for DSY2 and DSY3 (2020’s 50th percentile). An overheating checklist must be completed for residential developments.


Future proofed to achieve Zero Carbon on-site: All developments and district heating systems to be future proofed to achieve zero carbon onsite by 2050.


Calculation of unregulated energy consumption: Major development proposals should calculate and minimise carbon emissions from any other part of the development, including plant or equipment, that are not covered by Building Regulations, i.e. unregulated emissions.


Cost to occupant: To be reported if heating and hot water is to be provided by heat pumps.


On-site renewable: To be maximised regardless of whether 35% carbon emission reduction has been met or not.


Demand side response: Plans for demand side response and investigations into energy storage is required.

How to get involved

There are many opportunities to support LETI, including volunteering your time and expertise. Subscribing to our mailing list is the best way to keep up to date with what we are doing:

→  Click here to sign up to the LETI mailing list