0.1 About CarbonLite Retrofit (CLR)

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What is CarbonLite Retrofit?

CarbonLite Retrofit (CLR) is the latest addition to the AECB CarbonLite family. The original CarbonLite Programme (CLP) focuses on new buildings. Now, CarbonLite Retrofit provides knowledge that is specific to retrofit.

There are two elements to CarbonLite Retrofit:

  1. CarbonLite Retrofit Online Training Course
  2. CarbonLite Retrofit Self-Certification Scheme for low energy retrofit projects

Completion of the CarbonLite Retrofit course will enable the person designing or overseeing a retrofit project to self-certify their retrofit project at the design stage and at the build stage.

However, the course is not just for those overseeing retrofit projects, as explained below.

1. CarbonLite Retrofit Online Training Course

Central to CarbonLite Retrofit are three key principles:

  • Heating energy should be used much more efficiently while at the same time
  • Comfort should increase, and
  • Health of occupants and of building fabric should be protected and enhanced.

1.1 Course Content

By completing the CLR course, participants will learn:


  • Why a moisture-robust, fabric-first approach to low energy retrofit is beneficial
  • How to achieve it


The aim is to enable retrofitters to achieve improved buildings that enjoy:

  • A future-proofed increase in winter and summer internal comfort levels
  • Excellent indoor air quality
  • Low running costs with a minimal energy performance gap
  • Retrofit strategies that are ‘economically optimised’ for owners and occupants
  • CO2 savings at low to negative cost per tonne of CO2 saved
  • Avoidance or reduction of risks from unintended consequences related to moisture

The diagram below shows the key themes covered in the course. Participants will learn how building fabric, building services and the UK climate combine to affect the balance of heat and moisture in our homes. This in turn affects the health of the building and the health and comfort of the occupants. Every aspect has an associated cost or cost benefit.

CLR overview summary diagram (Source: Tina Holt)
CLR overview summary diagram (Source: Tina Holt)


1.2 CLR course structure

The course is divided into 8 Modules (in addition to this one – Module 0), and each Module contains a number of lessons.

Every lesson contains text, images and links to further reading. Most lessons will have quiz questions at the end for participants to check their level of understanding.

Graphs, diagrams and photographs of construction details (such as the photos below) are used throughout.


1.3 Undertaking the CarbonLite Retrofit course gives:

  • Access to the AECB online retrofit training course and quiz style exam platform
  • License to use the AECB retrofit project certification system
  • Access to retrofit practitioner communities to share with and learn from others via discussion, project monitoring, analysis and case studies
  • Guidance on space heat demand reduction targets for retrofit and involvement in developing these into Retrofit Energy Standards
  • Access to the AECB Knowledgebase, an online searchable resource of over 200 articles
  • Encouragement to add your projects to and compare them with others on the Low Energy Building Database.
  • Access to discounted project finance from Ecology Building Society (as have any retrofitters who meet the EBS criteria).

The CLR training course is also part of a programme of research to increase theoretical and practical understanding of how to safely improve the performance of the UK’s existing buildings. By engaging in the programme, and monitoring and sharing results, all CLR participants will be able to contribute to the development of better low energy retrofit.

1.4 Who is CLR for?

CLR contains information for everyone involved in retrofitting. However, the focus of different professions will vary and some will need to go into more detail than others.

  • Design & construction professionals
  • Building owners
  • Builders
  • Trades
  • Property Managers
  • Building Control and Planning Officers
  • Energy consultants
  • Manufacturers
  • Policy & decision makers

1.5 Policy Note

CarbonLite Retrofit has been designed with the UK’s current and future green house gas (GHG) emissions targets in mind.

To achieve a space heating reduction of 50% across the entire UK dwelling stock, some properties will need to cut space heating consumption by up to 80%. Ironically, the so-called “hard-to-treat” homes are those where dramatic reductions of up to 80% can be most achievable.

So the CLR approach focuses on retrofit activity that would achieve reductions of around 50%-80%  in space heating demand and associated GHG emissions.

2. CarbonLite Retrofit Online Certification

As for the CarbonLite Silver Standard, CarbonLite Retrofit is a self-certification scheme.

  • On passing the CarbonLite Retrofit course, retrofitters can use the certification system.
  • The certifying consultant signs a form of declaration (the AECB does not currently audit or take responsibility for the certification).
  • Certification makes explicit the project’s claim to be a well conceived and implemented energy efficient retrofit.
  • The scheme provides the consumer with a degree of protection under trading standards – without the AECB having to get involved in quality control and legal matters.
  • The responsibility for performance claims lies clearly with the person signing the certificate and a duty of care on the client to ensure that the consultant is competent and suitably insured.


There are two elements to CarbonLite Retrofit:

  1. CarbonLite Retrofit Online Training Course
  2. CarbonLite Retrofit Self-Certification Scheme for low energy retrofit projects


Lesson tags: AECB, CarbonLite Retrofit, CarbonLite Retrofit certification, CLR, CLR certification, fabric first, low carbon retrofit, low energy retrofit, moisture robust retrofit
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