INCA Case Study: Mount Pleasant, Stevenage

Background of the Project

Stevenage Borough Council, located in Hertfordshire, England, is responsible for a population of over 87,000 residents. The council oversees a diverse range of properties, including numerous social housing units that are integral to the community’s housing strategy. The council is committed to improving living conditions, reducing carbon emissions, and enhancing the aesthetic appeal of its housing stock.

The Mt Pleasant retrofit project in Stevenage Borough Council was initiated under the Social Housing Decarbonisation Fund (SHDF) in the UK. The primary aim was to transform outdated and inefficient social housing into modern, energy-efficient homes, addressing both environmental and social needs. Prior to the retrofit, the properties in Mt Pleasant were characterized by a worn and dated appearance, with overgrown grass and a brutalist architectural style that clashed with the surrounding newer developments. This led to a negative perception of the area, impacting both the residents’ pride in their homes and the overall neighbourhood aesthetic.

Residents of Mt Pleasant faced high energy bills due to poor insulation, and the buildings were becoming increasingly difficult to maintain. The council aimed to achieve an Energy Performance Certificate (EPC) rating of A for the property, thereby significantly reducing energy consumption and costs for residents, while also enhancing the visual appeal of the area to match the standards of nearby private developments.

The wider impact of this project on the community includes the potential for increased property values in the surrounding areas and improved community perception. By enhancing the appearance and energy efficiency of the social housing units, the project helps to create a more attractive and sustainable living environment, encouraging community pride and cohesion.

Solution and Specification

The project employed a Saint-Gobain Weber’s webertherm XM external wall insulation (EWI) system, with specifications in line with PAS 2030 requirements for weathering and thermal bridge control.

Pull-out tests were conducted to ensure the right system was specified. PJ Mear Ltd, a Weber-recommended applicator, was well-versed in the stringent processes conducted by Weber to ensure compliance with multiple regulations.

Taking a fabric-first approach, PJ Mear ensured compliance and quality workmanship.

Weber Specification Manager Julian Still worked with PJ Mear to gather information for the project, for developing accurate project information pack, and PJ Mear then developed a location-specific method statement, resulting in better planning, coordination, and on-time delivery of the project.

Key specifications included in the PIP:

• Insulation Type and Thickness: 120mm mineral wool insulation was used throughout the project to ensure high thermal performance.
• System and Finishes:
  • webertherm XM Silicone System (MFD): A 1.5mm silicone grain texture in the colour “Winter White” (RAL 9003) was applied over a base coat and mesh layer.
  • webertherm XM Brick System: Weber Wall brick adhesive was used to lay interlocking brick slips in the colour “Sanded Slate” (RAL 70224), providing a modern and durable facade.

The render protected EWI system, based on non-combustible mineral fibre, mechanically fixed, with mesh cloth reinforced render and a textured finish, is capable of compliance with PAS 2035/PAS 2030:2019, applied on masonry substrate.

The project achieved a significant reduction in U-values, with the post-retrofit U-value achieving 0.27W/m²K, significantly lower than the pre-retrofit value of approximately 2.35 W/m²K, thus enhancing the thermal efficiency of the buildings.

Materials were handled and stored according to Weber’s stringent guidelines to prevent damage and ensure longevity. Dry-bagged products were kept off the ground and protected from water damage, while wet pre-mixed materials were stored frost-free and shielded from extreme heat.

Installation and Challenges on Site

The installation process faced several challenges due to the varied finishes of the buildings and the need for modern aesthetic upgrades, along with initial delays in commencement of works on site. One of the key challenges was the integration of gas pipes within the EWI system. Instead of running the pipes externally, which was aesthetically unpleasing, a 225mm gas box was installed, with vented covers matching the brick colour to ensure a seamless look.

Weber applications manager Linda Twidale visited the site before the works began to conduct toolbox talks and supported PJ Mear in assessing the suitability of the design and specification to understand areas of iteration before the works began.

Coordination among multiple stakeholders, including the main contractor Wates, the installer PJ Mear Ltd, and the product supplier Weber, was critical to keeping the project on timeline.

Regular site visits coupled with on-site toolbox talks were conducted to ensure that the installation adhered to the specified standards. The webertherm XM system required precise application, including weather constraints management and precise mixing and application of renders and adhesives.

To minimize disturbance to tenants living in the property during construction, residents were notified well in advance through letters and direct communication about the schedule and expected activities. A dedicated Resident Liaison Officer was available to address any concerns. The team maintained a clean and respectful work environment, with designated break areas away from resident access. This careful planning and consideration ensured that residents experienced minimal disruption and could continue their daily lives with as little inconvenience as possible.

Problems Overcome

The standard method of extending gas pipes past the insulation and running them outside the building was aesthetically displeasing to the Council. As a solution, a 225mm gas box was installed to enclose the pipes, with the insulation adjusted around these boxes. Weber provided guidance on sealing techniques to ensure system integrity. The boxes were colour-matched to the brick slips to maintain the overall aesthetic, and vents were incorporated to ensure safety compliance. This approach not only met the Council’s aesthetic requirements but also ensured the functionality and safety of the gas pipes.

Another issue was the limited space above top-floor windows, which required a custom solution. To address this issue, an L-shaped PVC trim with compressed mineral wool behind it was installed, maintaining thermal performance without creating a cold bridge. This solution was collaboratively designed with input from Weber and approved by the main contractor. The trim was discreetly integrated into the building’s facade, ensuring a seamless look while providing the necessary insulation. The implementation involved measurements and custom fittings to ensure a perfect fit, demonstrating the team’s commitment to excellent workmanship and quality.

These solutions highlight the team’s ability to address complex issues through innovative thinking, detailed planning, and effective communication.

The End Result

The Mt Pleasant project resulted in two blocks with four dwellings each, transformed into aesthetically pleasing and energy-efficient homes. The properties now boast a dignified appearance, with modern finishes, enhancing the community appearance, aligning with nearby private developments, and contributing positively to the community’s overall look and feel, improving the residents’ pride in their homes.

The project’s success was due to the effective collaboration between PJ Mear, Wates, and Weber, leveraging their combined expertise to overcome challenges swiftly and maintain high-quality standards throughout the installation process.

Project commenced on February 2024 and completed on schedule in March 2024

For complaint handover O&M manual and SWIGA Guarantees were issued.

Each challenge was met with a tailored solution that balanced functionality, aesthetics, and resident satisfaction, contributing to the project’s success, which was completed on schedule despite facing initial delay.

The project achieved the desired EPC A rating, significantly improving the thermal performance and reducing energy costs for residents, ensuring long-term energy efficiency and reduced carbon emissions.

Client Comments / Quotes

Sam Turley, PJ Mear Ltd:

“The decades of experience within PJ Mear, Wates, and Weber meant that challenges were quickly solved through our combined knowledge, ensuring the project stayed on track and delivered high-quality results.”

Julian Still, Weber:

Our close collaboration with PJ Mear and Wates ensured that the EWI system was installed effectively, meeting all performance and aesthetic requirements, a good product needs a good applicator, so that the resident can have good quality of life”

Martin Asmantas, Project Manager, Wates:

Last year, Wates made the decision to partner with PJ Mear Ltd, to deliver external wall insulation works as part of the Stevenage SHDF WAVE 2 contract introducing energy efficiency measures to hundreds of existing homes thus transforming many local lives. Our decision seemed to have paid off, as just as our client, Stevenage Borough Council, we are extremely satisfied with the quality of finish achieved to date by our supply chain. One of the prime examples of our fruitful cooperation is the two Mount Pleasant blocks. We hope to maintain our successful collaboration with PJ Mear while continuing to reduce fuel poverty in the area and contributing to the upscaling of the town under the Stevenage Regeneration scheme to achieve an even Better Stevenage for all its residents.

Client Representative, Stevenage Borough Council: The comment has come via Rebekah Brydon, the Project Manager for the Stevenage SHDF W2 scheme:

“SBC is extremely pleased with the EWI works PJ Mear undertook on behalf of Wates. The new visual presentation of these blocks undoubtedly elevates the image of the area, and I`m confident our residents will soon see other tangible benefits of these energy efficiency measures, most likely in the form of reduced electricity bills and increased thermal comfort”.