Gentoo Group is a housing association that provides more than 60,000 people in Sunderland with a place they can call home. Gentoo is the largest provider of social homes in Sunderland. The housing association secured joint funding from the then Department for Business, Energy and Industrial Strategy (BEIS) from the Social Housing Decarbonisation Fund (SHDF) Wave 1 to improve the Energy Performance Certificate (EPC) rating of low performing properties.

The Whinfell project aligns to Sunderland Council’s ambition to be carbon neutral by 2030 and Gentoo is committed to having all its properties at an EPC rating of C or above by 2030.


Asset data provided on the seven terraced houses and 13 bungalows on the Whinfell estate in Sunderland, all constructed with calder timber frames, showed poor EPC D and E ratings with starting heat demand of 300 kWh/m2. The project was designed to deliver a deep retrofit fabric-first approach, including new windows and doors, external wall insulation, flat roof insulation and a whole-house ventilation strategy to reduce heat demand levels and achieve an EPC C standard rating.

Before: The homes were a prefab post-war design

Following a thorough review of the data, retrofit assessments were undertaken across each individual property to determine the most appropriate solution to tackle the issues faced. The team undertook a critical appraisal on the initial proposed solutions in order to determine suitability and understand other innovative solutions that may not have been considered.

The solution was to replace flat roofs with 200mm PIR insulation and single-ply membrane. The asbestos strip was removed and insulation of 90mm PIR between the existing timber frame studs was added. Calcium silicate board with a 140mm insulation and 10mm render as a system was installed throughout. Airex smart air bricks were installed to fit underneath the timber floor ventilation, while the internal shed wall was also upgraded. Windows and doors were replaced and the detailing around the windows and DPC were installed to PAS 2030 standards.

The work took around 36 weeks to complete and saw each property’s standard assessment procedure (SAP) score increase on average by 21 points.

Energy efficient windows and doors were also installed into all properties to provide high performance and help reduce bills. Optimisation works to the heating systems have taken place, weather compensation has been introduced and reduced flow temperatures, to further increase efficiency.

Resident-first approach

Positive and clear communication with residents about the scope of works was essential for the successful delivery of this scheme. Before work started, home visits were carried out to each property to discuss the individual needs of the customers and create a programme of delivery around their personal circumstances and lifestyle. This helped Gentoo to keep the scheme on programme and minimise disruption for residents. The housing association also used this as a key opportunity to provide details of the dedicated Customer Experience Coordinator assigned to each property, as well as sharing educational literature and factsheets to explain the benefits of the proposed asset upgrades.

Residents were invited to a coffee morning to discuss the scope of works with representatives from both Gentoo and RE:GEN. This gave the opportunity for tenants to view the proposed plans and discuss some of the technical elements of the project including the airex system.

Robust health and safety measures were put in place to keep residents safe at all times. Due to the age and vulnerability of some of the residents, suitable accommodation had to be found for relocation while the works were being carried out, especially whilst removing asbestos. Communication was vital – customers were updated after air tests were completed and it was safe to return to their homes.

Due to ill health, one tenant hadn’t left their home for three years so this was a huge challenge to overcome. Communication and engagement was therefore extremely important. Gentoo made sure that their needs were met throughout the entire process, including facilitation to temporary accommodation and offering as much care and support as they could to make sure they were comfortable.


Working closely with tenants from the start of this project, the 20 properties were transformed into highly efficient homes in just eight months. Residents are now experiencing a huge improvement in energy efficiency. The average heat demand level per property has been reduced from 300 to 169 KWh/m2/annum with all properties now achieving EPC C standard. The average annual fuel cost saving for tenants is around £448 per property, tackling fuel poverty with an average SAP improvement is 22 points per property, and reducing the amount of carbon each property produces by 2.5 tonnes.

Tenants are seeing a big improvement in thermal comfort and will benefit from lower energy bills. Two customers have agreed to have their energy bills monitored, to promote the savings this scheme delivers. Whinfell tenants have reported 100% satisfaction with the works undertaken.

The homes were leaking and wasting energy and the impact of the residents’ use of these properties was significant. This was in addition to the impact these properties were having on fuel poverty and general comfort. The work has also improved the appearance of the area as these homes were a prefab post war design and now have a clean and modern appearance and are fit for the future.

Following completion, Gentoo asked tenants to fill in a satisfaction survey. Out of all the tenants surveyed in January, 100% were satisfied with the work that had been carried out in their home.

The Whinfell retrofit scheme sees completion.

Not only will these works enable Gentoo to align its targets to Sunderland’s Net Zero 2030 target, it also supports the local community and the residents living in these homes by alleviating fuel poverty. With customers agreeing to have their energy bills monitored to promote the savings of this scheme, there is an aim to boost adoption of deep retrofit works across the region.

As part of its wider business strategy and understanding its carbon footprint, RE:GEN Group undertook an assessment of the carbon footprint of the site and introduced measures to reduce this through site operations. Throughout construction, their site cabins were powered using renewable energy and they achieved 95% recycling rates (not including asbestos).


A key learning from this project that has influenced their joint approach moving forward is the importance placed on communication with tenants. Engaging with tenants around the benefits of greener homes is essential to ensure buy in and support throughout.