London Borough of Harrow – SHDF Wave 2.1 / SHF Wave 3 

Harrow, South East England 

Project Value: £2.7m (phase 1)

Introduction

In 2025, SBS was appointed to manage a residential decarbonisation scheme for the London Borough of Harrow. The first part would be funded by Wave 2.1 of the Social Housing Decarbonisation Fund, and follow-on works would be supported by Wave 3 of the Warm Homes: Social Housing Fund. In all, the two phases would deliver multi-measure improvements to 240 homes – many of which were originally built to non-traditional designs.

Procured through a direct award, the project would encompass a range of fabric-first improvements, including external wall insulation, replacement doors and double glazing, new loft insulation, and ventilation improvements. In some cases, cavity wall insulation and solar PV panels would be installed.

The overarching aim of the scheme was to raise average EPC band ratings to a score of C or better.

The Project

Many of the homes were originally constructed to the prefabricated BISF design. These steel-framed properties were built in large numbers shortly after the Second World War to help address the UK’s housing shortage. In this construction type, relatively thin concrete or asbestos cement panels form the infill between the steel frame components, resulting in poor thermal performance. Common issues associated with BISF properties include significant heat loss, interstitial condensation, corrosion of the steel frame, resulting structural deterioration, and the potential for damp ingress.

To establish the condition of each property, the project team carried out detailed, property by property inspections. These assessments examined the strength and integrity of the existing substrate, including the steel stanchions and concrete foundation slabs, ensuring that any necessary structural remedial works could be identified and completed before retrofit measures were installed.

Working on a whole-house approach to maximise economies of scale, the project team collaborated from the earliest design stage to develop tailored retrofit plans in accordance with PAS standards. Informed by the individual property surveys, these plans identified the most appropriate and cost-effective measures for each home, while also enabling site teams to mobilise efficiently and deliver the programme at pace.

The project funding imposed tight deadlines on site managers and installers, so a key challenge was to put in place fast, efficient procedures, backed by a strong and effective multi-stakeholder team. This team included SBS, other retrofit role specialists, client representatives, structural engineers, system designers, and various other supply chain partners.

SBS made its first site visit in early September 2025. Once there, managers secured a site office, mobilised a full site team, procured a full sub-contract team and began preparatory works.

The first Wave 2.1-funded phase entailed works to 67 homes. 34 of these were BISF and Orlit properties (non-traditional), which, in addition to the fabric-first improvements, would benefit from new soffits, facias and gutters, improved internal ventilation, and the removal of asbestos-containing materials in the loft spaces.

The other 33 homes, featuring more traditional archetypes, would have new solar PV arrays, loft insulation and internal ventilation works.

Results

Phase 1 scaffolding works commenced on 28th October 2025. Aided by the detailed surveys and multi-stakeholder support, the team then made rapid progress. The first handovers took place on 11th February 2026 and continued at pace. All Wave 2.1-funded retrofit works were lodged and completed on time.

The second, Wave 3-funded phase began in February 2026 and entailed similar works to a further 173 homes. These comprised:

• 111 BISF and Orlit non-traditional properties. (Same scope as for Wave 2.1)
• 62 traditional properties. (Scope: cavity wall insulation, loft insulation and ventilation works)

At the time of writing, the Wave 3-funded works were progressing well, with completions running 2 weeks ahead of schedule. Against a targeted ‘time in property’ of 12 weeks, installers averaged just 10 weeks per residence. All indications suggest that the homes will achieve EPC band ratings of C or better, as planned.

Social Value

In addition to improving the homes’ energy efficiency and appearance, the works will help residents to minimise their routine energy bills and to enjoy warmer, more comfortable living conditions. They are also likely to generate substantial savings on carbon emissions – a vital step in the country’s efforts to move towards net zero.

During the scheme, the stakeholder team also sought to ensure that the works would yield added social value in the form of training and employment opportunities, and – wherever possible – by keeping project expenditure within the region.

Further social value measures will be delivered as the second phase of the project continues.

Client Feedback

Billy Reid, Assistant Director from Homes, said: “The work that has been delivered by SBS so far has been of extremely high quality, which has led to overwhelmingly positive feedback from residents.

“We’re pleased that households will benefit from warmer homes and lower energy bills following the residential decarbonisation programme. Meanwhile, we will be helping to reduce carbon emissions and move closer towards net zero. It’s a win-win situation”

Resident Feedback

Over the course of the scheme, site staff received numerous texts and emails from residents. Shown below is a selection of their comments.

• “I’m really happy with the works so far. All workers are cooperative, and they’re always keeping me up to date. Thank you.”
• “Thank you, the work has been lovely, and all operatives have been very helpful.”
• “The two guys who came to do the fans were so clean and tidy. They even cleaned my front door step, which they didn’t have to. They went above and beyond; nice people.”
• You and your contractors have been great. I appreciate it. Council tenants themselves find this whole process exciting… From what I see, the job has been amazing; such a big job to coordinate too.”
• “The men who did the rendering were really good, and they left my property very tidy. So happy with how the work is going. My house is starting to feel warm.”