Novel Whole House Retrofit Approach

Domestic buildings are responsible for approximately 25% of the UK’s overall CO2 emissions. The current UK domestic housing stock comprises 26m homes, of which around 80% will still be in existence by 2050. Given the scale of demand that this stock places on the UK energy system, it is critical to develop cost-effective solutions to improving the thermal efficiency of existing dwellings in order to potentially reduce domestic energy consumption. The Energy Technologies Institute (ETI), a public-private partnership between global energy and engineering companies and the UK Government, having developed a theoretical novel whole house retrofit approach, has now commenced the testing of the approach in five properties.

The ETI announced the launch of the Domestic Retrofit Project in May 2014 and has appointed a project team from PRP Innovate to lead a consortium that includes Peabody, one of London’s largest housing associations and community regeneration providers. The retrofit work will be carried out and managed by VINCI Facilities. This project is part of the ETI’s Smart Systems and Heat programme, which aims to create future-proof and economic local heating solutions for the UK.

The aim of the 20-month long project is to establish an affordable, whole house retrofit solution with quality at its center, which produces a solution that can be carried out effectively on a large scale across different house types. The novel whole house retrofit approach being tested was first developed in a desk-based ETI project called ‘Optimising Thermal Efficiency of Existing Housing’ and focuses on four main areas.

1. Consumer’s acceptability

Retrofit needs to be consumer-focused, ensuring the delivery of a quality service.  Understanding consumer requirements is key to delivering the novel retrofit approach. Different consumers have different tastes and needs, and view levels of comfort differently. Another consideration is that consumers tend to be driven mainly by the potential for better comfort (e.g. warmer homes) and financial benefits (e.g. cash savings due to lower energy bills following retrofit implementation) and not CO2 savings.

The majority of the consumer’s interaction with the retrofit process tends to be with those carrying out the works. It has been identified that ensuring a single point of contact is in place between the retrofit team and the consumer is vital. This not only fosters a positive relationship and instils trust, but also makes consumers more tolerant of any issues and more likely to recommend retrofit.

2. The energy efficiency solutions

Figure 1 shows a typical thermal image of a dwelling showing heat losses in red. To tackle such heat losses, two levels of intervention have been developed as part of the novel retrofit approach. These allow for packaged work (rather than individual measures), whilst also offering different options based on consumer preference, cost and the level of disruption. The RetroFix® package (providing predicted average energy savings of ~33%) is designed to tackle the most significant thermal losses in existing housing stock. The package for each house type – depending on its age and construction – typically includes wall insulation, loft and ground floor edges insulation, improved airtightness, and heating system and control upgrades. Providing predicted average energy savings of ~50%, the RetroPlus® package includes all of the improvements in RetroFix® plus further thermal improvements to floors, doors and windows and more innovative heating systems where appropriate.  

Typical thermal image of dwelling (Courtesy of Peabody)

3. The effectiveness of the delivery mechanism & supply chain

Changes to the retrofit delivery process offer the greatest potential financial savings for both the retrofit teams and the consumer. ETI’s research has reviewed current processes and identified areas for improvement which the ETI believe contributes significantly to higher project costs through inefficiencies in labour utilisation and material wastages.

When addressing labour inefficiencies, the most important changes to the process involve the introduction of a ‘poly-competent’ team, where all required skills for retrofit are within a team of four installers, who are then dedicated to each individual house retrofit. Rather than using individual tradespeople, the model is based on a team trained and accredited (to the level required to complete retrofit tasks) to deliver the core retrofit tasks to a high standard. The team-leader will hold the required expertise to certify the regulatory requirements of the works and will act as the single point of contact for the consumer. The evaluation of the effectiveness of the poly-competent team is a key element of the Domestic Retrofit project.

With regards to the standardisation of processes and material wastages, greater integration between the installer and the supplier and the use of pre-cut materials in a single delivery provides a significant opportunity in eliminating ‘non-value-adding activity’ from the entire process. This creates the best possible value result for the consumer.

By reducing labour utilisation inefficiencies and material wastages, and by streamlining the retrofit process, the project seeks to identify the most cost-effective solution for each of the two interventions,  to attract consumer uptake for the novel approach. To meet consumer expectations, the retrofit works need to be completed in the shortest time possible.

4. The commercial viability

One of the key aspects of the novel whole house retrofit approach is to evaluate the attractiveness of the commercial offering to the consumers. The novel approach will identify, analyse and discuss the problems, gaps, issues and barriers, and undertake an assessment of the commercial viability of this approach – including the trade-off between costs, time and standard of finish versus thermal efficiency. There is considerable variation in build quality and standard in existing properties and each is likely to require different degrees of improvements. Therefore, understanding the range of costs given the state of the property is critical to evaluating the offerings to consumers. This novel approach also looks at how existing incentives such as Green Deal, Energy Company Obligation (ECO) and other streams of funding can help further to support the case for the whole house retrofits.


Although this project is only an initial step to validate the novel whole house retrofit approach on a small number of properties, the novel approach employs a holistic approach that addresses all four areas mentioned above. In order to contribute to the UK’s legally binding target of an 80% reduction in CO2 emissions by 2050, there is a need to change current methods and introduce innovative cost-effective solutions that are attractive to the consumers in raising their comfort levels whilst also lowering their energy bills. Alongside this, the solutions need to be commercially attractive with shorter consumer payback periods.

For further information
please contact Mohammed
Ali, Project Manager at the
ETI for the novel whole
house retrofit (E-mail:


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