INCA EWI Case Study: Pen y Dre High School, Merthyr Tydfil

Wetherby Wall Systems Helps Deliver Wales’ First Major Net-Zero Carbon Refurbished School

A pioneering net-zero carbon refurbishment led by Morgan Sindall Construction and Merthyr Tydfil County Borough Council is transforming Pen y Dre High School into Wales’ first major net-zero carbon refurbished school. Central to the transformation is the installation of a high-performance A1 fire-rated external wall insulation system from Wetherby Wall Systems, helping convert the existing 1970s building into a modern, sustainable educational facility for more than 1,050 pupils while remaining fully operational throughout the three-year construction programme.

Located near the highest point of the Heads of the Valleys Road in South Wales, Pen y Dre High School occupies an exposed site approximately 500 metres above sea level. The ambitious multi-million-pound programme has transformed the existing 1970s school into a modern, energy-efficient campus capable of supporting more than 1,050 pupils while remaining fully operational throughout construction.

Rather than demolishing and rebuilding the school, the project team adopted a refurbishment-first approach, significantly reducing embodied carbon while preserving valuable community facilities including the school’s swimming pool, sports halls and dining hall. The result demonstrates how existing public buildings can be successfully upgraded to meet modern sustainability standards while continuing to serve the communities that rely upon them.

The comprehensive refurbishment programme included new roofing, cladding, windows and external doors, extensive mechanical and electrical upgrades, internal remodelling, new finishes and furniture, and a complete transformation of the building envelope. Central to achieving the project’s ambitious performance targets was the installation of a high-performance A1 external wall insulation solution designed and supplied by Wetherby Wall Systems.

For the external works, Wetherby specified a robust system incorporating 200mm A1-rated ROCKWOOL DD Slab insulation, delivering outstanding thermal performance whilst meeting the highest fire safety standards. The system was designed to dramatically improve the thermal efficiency of the existing building and withstand the challenging weather conditions associated with the school’s elevated location.

To maintain the character of the original building whilst creating a contemporary appearance, Wetherby’s innovative Laguna Clay Brick Slips were selected for the façade. Unlike traditional cut brick slips, Laguna slips are manufactured to their finished thickness, delivering improved consistency, tighter tolerances and a more sustainable solution while accurately replicating the appearance of conventional masonry. The completed façade provides a durable, high-quality finish that complements the building’s transformation while ensuring long-term performance in this exposed location.

The Live School Challenge

One of the most significant challenges facing the project team was delivering an extensive three-year refurbishment programme while keeping the school fully operational.

Works were carefully planned and delivered across six phased stages, allowing teaching staff and pupils to continue using the school throughout construction. This approach required exceptional coordination between the client, design team, contractors and school management, ensuring disruption was kept to an absolute minimum while maintaining the highest standards of safety.

Alongside the logistical challenges of working in an occupied educational environment, the project team also addressed asbestos management, structural issues and contamination associated with the existing 1970s building. Through close collaboration and detailed planning, the team successfully overcame these challenges while maintaining programme deadlines and delivering a high-quality finished result.

Achieving Exceptional Thermal Performance

A key objective of the project was to dramatically improve the thermal efficiency of the building envelope.

Prior to refurbishment, the external walls achieved a U-value of approximately 1.6 W/m²K. Through the installation of Wetherby’s external wall insulation system incorporating 200mm ROCKWOOL DD Slab insulation, this was reduced to just 0.2 W/m²K, representing a significant improvement in thermal performance and energy efficiency.

The enhanced building fabric will help reduce energy consumption for decades to come, creating a more comfortable learning environment for pupils and staff while supporting the wider sustainability objectives of Merthyr Tydfil County Borough Council and the Welsh Government.

Delivering Net-Zero Results

Pen y Dre High School stands as a flagship example of sustainable refurbishment.

The decision to refurbish rather than rebuild delivered four times less carbon impact than a comparable new-build scheme, demonstrating the environmental benefits of retaining and upgrading existing buildings wherever possible. The project also incorporates a substantial photovoltaic array that contributes towards the school’s net-zero carbon status while providing surplus energy to neighbouring public facilities through a direct-wire connection.

To date, the project has already achieved carbon savings of approximately 619 tonnes through operational efficiencies, making a significant contribution towards local and national decarbonisation targets.

Beyond environmental performance, the scheme has delivered substantial social value benefits. These include the creation of 42 new entrant jobs, 3,389 training and engagement opportunities, and a workforce made up of 95% locally sourced labour. These achievements ensure the long-term benefits of the project extend far beyond the school itself and into the surrounding community.

Voices from the Project

Robert Williams, Area Director at Morgan Sindall Construction Wales, said:

“This has been a truly pioneering project. The scale and complexity of delivering such a comprehensive transformation within a live school environment cannot be overstated, and our teams have responded with exceptional skill and dedication throughout. We are not only creating a world-class educational facility for future generations, but also demonstrating how sustainable refurbishment can dramatically reduce carbon impact whilst delivering meaningful benefits for the local community.”

Sophie Jenkins, Sustainable Communities for Learning Programme Manager at Merthyr Tydfil County Borough Council, said:

“Some people would tell you that a refurbishment project could never be as good as a new build project. After working with Morgan Sindall, I’m not one of those people. I’ve been astounded by the quality of the final works and the genuine collaboration throughout the project.”

Alex Smith, Project Manager at Morgan Sindall, added:

“Speaking on behalf of the client and everyone at Morgan Sindall, I’m very proud of this project and the striking appearance of the Wetherby brick slips. Credit too to Joyner Group who delivered the installation on time despite the challenging conditions associated with such an exposed location.”