Climate Emergency Retrofit Guide

LETI’s Climate Emergency Retrofit Guide shows how we can retrofit our homes to make them fit for the future and support the UK’s Net Zero targets.  We define energy use targets for existing homes and provide practical guidance on how to achieve them.  

The guide is useful for architects, engineers, Local Authorities, social landlords, energy professionals, contractors and clients looking for guidance about best practice retrofit.

It is widely accepted that retrofitting our existing buildings is absolutely critical if we are to achieve Net Zero.  Around 18% of our annual national CO2e emissions come from existing homes – homes that will still be standing in 2050. 80% of 2050’s homes have already been built.  It is also widely acknowledged that the retrofit challenge is monumental.  Over one million homes every year for the next 30 years will need to be retrofitted.  We cannot afford to retrofit them twice.  But if we retrofit them well, we can enjoy many environmental, social and economic benefits.

This guide sets out what good retrofit looks like for existing homes.   We target energy consumption reductions of 60-80% for the average UK home.  This is achievable through a whole house approach upgrading the building fabric, incorporating energy efficiency measures, improving ventilation and fitting heat pumps. These targets have been determined through practical experience and understanding of what measures are realistically achievable.  They are also informed by a national housing stock model to examine issues such as renewable energy provision and grid capacity. The guide also points out the potential risks of poor retrofit and advises on how to deliver efficient, resilient and healthy homes. 


Quick start guide

The guide provides a quickstart guide to retrofit as well as typical house archetype examples for four primary housing types: semi-detached, detached, mid-terrace and a flat.  Click on the pages below for the quickstart guide and typical house archetype examples.

Author: LETI

Publication date: October 2021


Video – Net zero and the role of MMC

The first event in conjunction with out Build Net Zero Now campaign. 


Easi Guide to Passivhaus design

Levitt Bernstein, alongside sustainability engineers Etude, have campaigned tirelessly for faster change in the built environment to achieve zero carbon. But they have found that often the best way to effect change is to collaborate with others, lead by example and share learning along the way.

They believe that the first step to zero carbon is to create an ultra-efficient building design. Through their project work with Etude, they have discovered that the benefits of low energy design can be unlocked by viewing Passivhaus considerations as an opportunity, rather than a constraint.

This led them to develop the ‘Easi Guide to Passivhaus design’, which has been endorsed by the Passivhaus Trust.

The guide graphically sets out ten simple principles that form the foundations of good Passivhaus and zero carbon design. They encourage clients to use it to set their briefs and architects to use it when designing their buildings. The main body of the guide emphasises key considerations at RIBA Stage 2 to allow design teams to meet Passivhaus within the contextual needs of their site, while a checklist offers the next steps if full certification is to be pursued.

By providing open access, they hope that you enjoy our guide, make many zero carbon buildings and share your learning with others.

Author: Etude/Levitt Bernstein

Publication date: June 2020



Delivering Net Zero Homes: Tutorial 1 Design

The first in a series of hour-long interactive online tutorials with guest industry experts on how to deliver net zero homes. The presenters discussed key issues in the delivery of net zero housing – design, costs and strategies.

Speaker: Tom Dollard, Head of Sustainable Design, Pollard Thomas Edwards

Tutorial date: Tuesday 21st April


Climate Emergency Design Guide

We are in a climate emergency, and urgently need to reduce carbon emissions, this guide outlines the requirements of new buildings to ensure our climate change targets are met – setting out a definitive journey, beyond climate emergency declarations, into a net zero carbon future. It is specifically aimed towards developers/landowners, designers, policy makers, and the supply chain. It aims to help to define ‘good’ and to set clear and achievable targets.

The Climate Emergency Design Guide covers 5 key areas: operational energy, embodied carbon, the future of heat, demand response and data disclosure. Our methodology includes setting the requirements of four key building archetypes (small scale residential, medium/large scale residential, commercial offices, and schools). The guide was developed by over 100 LETI volunteers over a period of 12 months.

This guidance demonstrates that the building industry knows how we should be designing buildings. In 2020 buildings that adopt these requirements now will be seen as leaders. By 2025 these requirements must become standard design practice otherwise the building industry will not meet our collective responsibility in this climate crisis.

LETI believe that in order to meet our climate change targets, in 2020 10% of all new projects developers and designers are involved in, should be designed to meet the requirements set out in this guide.


Author: LETI

Publication date: January 2020


Post occupancy evaluation of certified Passivhaus homes in the UK

The Passivhaus Trust has been working with Rachel Mitchell, Bath University and WARM to analyse the performance of a number of certified Passivhaus dwellings in the UK.

Monitoring data obtained from Technology Strategy Board (now Innovate UK) research projects has been included in the report, which mirrors the EU funded CEPHEUS research project that has looked at the performance of Passivhaus buildings across continental Europe. A total of 13 sites in the UK were monitored as part of the project, although the research is open-ended and we are able to add project performance data and update the research as and when it becomes available.

The research is focused on certified new-build Passivhaus homes, both single dwellings and multi-residential.

One key finding of the research is that the Passivhaus dwellings perform exactly as expected in terms of Space Heating demand.

Key measurement data:

  • Internal temperature for at least one year
  • Space Heat energy use (or total energy bills) for the same period as internal temperature
  • Source of heating

Additional measurement data:

  • External temperature
  • Solar radiation
  • The PHPP sheet for each dwelling
  • Occupancy levels
  • Electricity bills

Author: Passivhaus Trust

Publication date: July 2017


Case Study

Camden Passivhaus

Camden Passivhaus incorporates heat recovery ventilation, extremely good insulation and air-tightness, and high performance glazing to create comfortable and healthy conditions, and minimise energy requirements.

The project reported here is part of the Technology Strategy Board’s Building Performance Evaluation programme and acknowledgement is made of the financial support provided by that programme. Specific results and their interpretation remain the responsibility of the project team.

Author: Good Homes Alliance, Bere Architects, Jason Palmer, UCL, Alan Clarke

Publication date: 2014



Photo credits: Tim Crocker