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, Local Authorities and other organisations.


Originally ‘The London Energy Transformation  Initiative’, LETI was established in 2017 to support the transition of the London’s built environment to meet Net Zero Carbon. We worked 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 worked to develop consensus within UK industry on a definition for Net Zero Operational Carbon. In 2020, LETI launched the Climate Emergency Design Guide, which outlines requirements of new buildings to ensure our climate change targets are met. Supplementary guidance to the Climate Emergency Design Guide, on Embodied Carbon, was provided in the Embodied Carbon Primer.

in 2021, LETI published guidance on Hydrogen, Carbon Alignment, a Client Guide for Net Zero Carbon Buildings and the Climate Emergency Retrofit Guide.


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:

In 2020 LETI published the Climate Emergency Design Guide, which outlined requirements for new buildings to ensure our climate change targets are met.  Published in January 2020, it has been widely supported, adopted and cited by architects, developers, law makers and built environment professionals. It has been downloaded over 60,000 times in over 100 countries and its requirements are accepted and followed by building professionals across the UK. LETI is aware of over 30,000 homes and 1,000,000m2 of commercial floor space that are aiming to meet LETI’s new build targets.


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