Projects

AES Sustainability, one of the UK’s leading energy and sustainability consultants, has recently completed a comprehensive programme of assessment and retrofit improvements for Cambridge Housing Society (CHS).

This has delivered end‑to‑end retrofit assessment, air testing and improved coordination of sustainability solutions across 118 homes located throughout Cambridgeshire and Essex. It formed part of a wider strategic review by CHS.

The project began with AES assessing CHS’s broader portfolio of around 3,000 homes. From this early work, AES and property and construction consultancy McBains, identified 15 distinct archetypes that helped shape the client’s long‑term approach to asset improvement.

AES Sustainability also supported CHS with a funding application that successfully secured just under £1 million towards the delivery of retrofit assessment and works.

The homes included in the building retrofit programme varied significantly in age and construction type. Many of the oldest houses were pre‑1930 solid wall homes, with some featuring 1970s cavity wall extensions. Others were 1990s cavity wall construction. A small number of low‑rise flats were also included.

Before retrofit activity commenced, AES Sustainability undertook a detailed series of assessments to establish a reliable baseline. This included air‑tightness testing, borescope inspections, property typology verification, occupant surveys and the collection of technical evidence. These were requiredrequired for pre‑improvement Energy Performance Certificates (known as EPCs). These investigations helped inform a fabric‑first approach, designed to achieve an EPC rating of at least C.

Delivery of the retrofit measures required close collaboration between AES Sustainability and the primary contractor, Arann Insulation. AES Sustainability provided on‑site coordination throughout the project.

The team checked the sequencing of works was compliant with PAS2035, the industry framework for improving energy efficiency for existing homes.  This included ensuring the project was completed to the highest standard and that it complied with government guidelines.  They also acted as the liaison between contractor and the client. This approach was vital to keeping residents informed and supported at every stage.

AES Sustainability’s Retrofit assessors, coordinators and advisors were regularly present on site, offering the practical, day‑to‑day oversight required to maintain quality, resolve issues quickly and keep the programme moving efficiently. As part of the role, AES helped managed resident queries and feedback that came via CHS’s Asset Management team. This provided the human connection that frequently becomes the first and last point of contact for households undergoing retrofit works or assessment.

The measures installed across the 118 homes reflected their differing construction types and needs. Solid wall properties received external wall insulation (EWI) whilst homes with cavity walls benefited from new cavity wall insulation. Where appropriate, properties also benefitted from improved ventilation and new windows and doors, alongside loft and flat‑roof insulation. Several off‑grid homes received modern high heat retention storage heaters, while solar PV was installed on selected properties with suitable roof conditions.

One Cambridge property has provided a particularly clear illustration of the impact achieved. Following AES Sustainability’s retrofit assessment and design recommendations, the home was upgraded with new windows and doors, EWI, new loft insulation and improved ventilation.

The resident commented that she ‘couldn’t believe the difference’ the measures had made, emphasising both the improved comfort and the visual transformation of her home. Similar feedback was received across the programme, with residents consistently reporting positive experiences linked to AES’s on‑site presence and communication.

Quality assurance remained a central element of AES Sustainability’s involvement. The team completed full post‑retrofit assessments, air‑tightness testing, photographic and technical evidence gathering, and responses to audit requests.

These actions ensured full PAS2035 compliance and provided CHS with a clear, transparent record of the improvements delivered. Regular communication with the client ensured that any concerns or issues from residents were rapidly relayed and addressed. This supported high levels of satisfaction throughout the programme.

With all works across 118 homes completed and final documentation in preparation, the outcomes clearly demonstrate the value of AES’s integrated approach. By managing every phase - from initial portfolio analysis and funding support through assessment, design, coordination, resident engagement, contractor liaison and final compliance – AES Sustainability consultants have delivered a seamless retrofit experience that improved energy performance, reduced costs and enhanced comfort for households across the region.

Successful retrofit delivery relies as much on maintaining trust with residents as it does on technical expertise, and this programme of environmentally sustainable improvements exemplifies how both elements can be combined effectively.

AES Sustainability are a leading UK energy and sustainability consultancy. Get in touch to find out how we can help support your development at any stage of the cycle.