Why we use the LETI standard
An introduction to the standard guiding low carbon housing – and why it underpins community-led energy projects like CAPZero
Cutting carbon from our homes means having a plan that’s ambitious but also realistic for the houses we live in. That’s why CAPZero – our Community Action Plan for Zero-Carbon Energy, hosted by Low Carbon Hub – uses the LETI standard as its guide. It helps us set strong, practical targets for making homes genuinely low carbon, whether they’re newly built or retrofitted.
What is LETI?
LETI (the London Energy Transformation Initiative) began in 2017 as a voluntary network of architects, engineers, and planners tackling the UK’s building-related emissions. In 2020, it published the Climate Emergency Design Guide – a clear, practical set of targets for zero-carbon homes.
Since then, LETI has become a go-to resource for local authorities, developers, and community projects across the UK – including our work here in Oxfordshire with CAPZero.
Key ideas from LETI
- Low energy use – Homes should use as little energy as possible, with insulation and airtightness keeping them warm in winter and cool in summer.
- All-electric buildings – Running on electricity, not gas or oil, to match a greener grid.
- Use renewable energy – Generating clean power at home, such as with solar panels.
- Focus on real performance – Homes that perform well in practice, not just on paper.
- Build to last – Using sustainable, long-lasting materials to cut construction carbon.
- Retrofit existing homes – Upgrading older housing to be more efficient and less polluting.
Why LETI fits CAPZero
While some may know Passivhaus – the rigorous energy standard developed in Germany – LETI offers a more flexible approach. For a project like CAPZero, focused on real homes across Oxfordshire’s diverse neighbourhoods, that adaptability is essential.
Here’s why LETI is the right fit:
It’s practical for the real world
LETI sets ambitious energy targets (such as no more than 35 kWh per square metre) but allows flexibility in how they’re achieved. That could mean insulation, heat pumps, solar panels, or smart controls. This adaptability makes it useful for both new builds and retrofits – vital for a project like CAPZero that is addressing older homes as well as new developments.
It looks at the full carbon picture
LETI goes beyond day-to-day energy use (‘operational carbon’) to include the embodied carbon in materials – important as construction becomes a bigger part of the UK’s carbon footprint. CAPZero uses this whole-picture view to guide decisions on both upgrades and new housing.
It works with the clean energy future
Unlike older standards shaped around fossil fuels, LETI recognises that the UK is shifting to renewables. It encourages solar-ready design, battery storage, and all-electric heating – all of which align with CAPZero’s ambition to connect homes with a smarter, cleaner energy system.
It fits community energy goals
At its heart, CAPZero is about cutting carbon, reducing bills, and building local resilience. LETI provides the framework that ensures every home improvement moves us closer to those goals.
What about Passivhaus?
Passivhaus remains an excellent choice for ultra-efficient homes. But for the speed and scale of change needed across the UK’s mixed and often older housing stock, LETI offers a more adaptable, cost-effective route. We’re not pitching one against the other – but for a community-driven project like CAPZero, LETI is the better fit.
Retrofitting older homes
Most homes in Oxfordshire aren’t new builds, which is why retrofit is such an important part of CAPZero. Upgrading older houses can feel daunting, but it doesn’t have to be done all at once.
Through our partner service, Cosy Homes Oxfordshire, homeowners can get clear, independent advice on where to start – from small improvements to full whole-house plans. The aim is simple: to cut carbon emissions, lower bills, and make homes healthier and more comfortable to live in, step by step.
What you can do
If you care about low carbon homes and a fair energy future, you can:
- Support local energy initiatives like CAPZero and Cosy Homes Oxfordshire
- Ask your council to adopt LETI standards in planning and retrofit policy
- Spread the word about why practical, ambitious standards matter
The future of housing is being decided now. CAPZero, guided by LETI, is one way we’re making sure it’s built to last – and built for everyone.