INCA Case Study: Watford Community Housing Retrofit Scheme

Executive Summary

This project is a leading example of social housing retrofit excellence, spearheaded by Watford Community Housing in partnership with Kooka and EWI Pro. It involved the thermal upgrade of 285 solid wall homes using external wall insulation (EWI), with funding support from SHDF Wave 1 and 2. The primary goals were we scale to reduce energy consumption, combat fuel poverty, and improve the long-term resilience and visual appeal of the housing stock. EWI played a central role in meeting these objectives, providing not only energy efficiency but also aesthetic transformation and community benefit.

Project Background & Context

The homes targeted were primarily pre-1980s properties, typified by solid wall construction, poor insulation, and declining visual appeal. Residents often reported cold homes, mould issues, and high energy bills. The scheme aimed to align with local decarbonisation strategies and PAS 2035 requirements, addressing multiple performance gaps while uplifting entire estates in one of Hertfordshire’s key urban communities.

Technical Solution – EWI System Design

The EWI Pro EPS system was selected for its excellent thermal performance, durability, and cost-effectiveness. EPS thickness ranged from 90mm to 110mm, delivering post-installation U-values of 0.30 W/m²K, a substantial improvement from an average baseline of 2.2 W/m²K. Fixing included both mechanical and adhesive application, while the system featured alkali-resistant mesh and a silicone topcoat for flexibility and protection. The EWI system not only boosted energy performance but also extended the lifecycle of the building fabric.

Design Detailing & Aesthetic Strategy

Colour choice (RAL 28036 Magnolia) was selected to harmonise with local architectural character, create a uniform community identity, and enhance curb appeal. Some buildings incorporated banding or subtle detailing to maintain their original aesthetic. The result was not only functional but also a transformation that residents could take pride in. The silicone render ensures a long-lasting, crack-resistant and dirt-resistant surface, significantly reducing future maintenance requirements.

On some of the properties, a mixture of acrylic brick slips and silicone render were used to retain the traditional brick façade appearance while delivering the thermal benefits of EWI. This hybrid approach preserved architectural integrity and met planning sensitivities in specific areas.

Construction Methodology & Site Management

Delivering retrofit in occupied homes required a carefully phased approach, robust resident liaison, and high attention to quality assurance. Kooka Developments ensured minimal disruption by coordinating works block-by-block, scheduling around resident needs, and maintaining constant site safety and cleanliness. EWI Pro provided on-site technical guidance and inspections throughout. PAS 2035 coordinators ensured compliance with whole house retrofit principles.

Performance Outcomes & Measurable Benefits

The retrofit delivered major performance uplifts: energy demand dropped by 50–60%, SAP scores increased by up to 30 points, and EPC ratings jumped from E/F to C. Residents saw heating bills fall by up to £600/year, while comfort, warmth, and indoor air quality significantly improved. Thermal bridging was addressed through detailed junction and eaves design.

Innovation & Problem Solving

Key challenges included severe weather events, access to complex façades, and retaining architectural details. EWI Pro advised on additive use for cold-weather work and bespoke detailing. Complex pipe and meter arrangements were rerouted with minimal disruption. Coordination was key in ensuring continuity of service and compliance at every stage.

Resident & Community Engagement

A dedicated on-site Project Manager oversaw all communications and provided consistent support to residents throughout each stage of the works. Resident feedback was highly positive, with many highlighting warmer homes, enhanced visual appeal, and lower energy usage as key benefits. Several residents also took part in a promotional filming initiative, produced in collaboration with EWI Pro and featuring Kooka as the installation contractor.

Social Value, Skills & Sustainability Legacy

The project created local jobs, including training pathways for EWI application. Several installers gained new certifications through the scheme. The sustainability benefits are long-term: reduced carbon emissions (an estimated 300 tonnes CO₂ annually), improved public health, and stronger community resilience. The approach is now being scaled across Watford and surrounding districts.

Conclusion

This scheme exemplifies the gold standard of PAS 2035-led, fabric-first retrofit in the UK social housing sector. Its technical rigour, collaborative delivery, outstanding visual uplift, and quantifiable performance benefits make it a model for future net-zero delivery. We believe this project fully merits recognition at the 2025 INCA Awards as a leading example of EWI in action.