GS8 Thornwood Housing Development
LOCATION
Thornwood, Epping Forest, Essex
SECTOR
Residential Housing
THE BRIEF
The Thornwood housing development in Essex, delivered by sustainable housebuilder GS8, will provide 113 new homes designed to meet growing demand for environmentally conscious living. A core ambition for GS8 was to reduce the embodied carbon across the project, especially in high-impact areas like the concrete foundations.
GS8 sought a supply partner that could deliver robust sustainability credentials, transparency on carbon impact, and compliant technical specifications. Holcim was brought on board early to evaluate options and help drive carbon reductions through low-carbon concrete innovation.
What we achieved in numbers
3,000m3
Concrete supplied
28%
Carbon reduction from
CIIIA vs CEM I equivalent
48%
Potential carbon reduction with
ECOPact CEM VI vs CEM I
Solution
1. Early Engagement and Transparent Specification
Holcim was engaged at the concept stage, allowing early input into low-carbon material options. The ECOPact product range was introduced, backed by third-party verified Environmental Product Declarations (EPDs) aligned with EN15804+A2 standards. This provided GS8 with the clarity needed to assess carbon impact at a granular level.
2. Holistic Collaboration Across the Supply Chain
GS8 worked with sustainability consultant KLH Sustainability and structural engineers BW Murray to review multiple mix options. The team approved an FND2 CIIIA ECOPact mix for early pours, achieving a 28% embodied carbon saving compared to the CEM I equivalent.
3. Innovation in Mix Design: ECOPact CEM VI
During planning, Holcim introduced a pioneering ECOPact CEM VI mix, incorporating limestone filler and GCC under BS8500:2023. While not initially available at the local Harlow plant, GS8’s enthusiasm prompted Holcim to allocate silo space at the site—just 5 miles from Thornwood—to supply the CEM VI mix for future pours. This adaptation will deliver an even greater embodied carbon saving of 48% compared to traditional CEM I concrete.
“Our ambition for Thornwood was to create a sustainable community with materials that align with our environmental ethos. Holcim didn’t just supply concrete—they partnered with us to drive innovation and reduce our embodied carbon footprint. Their transparency and willingness to adapt made a real difference.”
George Stiff
GS8 Director
4. Verified Data Through EPDs
GS8 required robust carbon data to uphold its sustainability promises. Holcim’s EPD-backed mixes enabled evidence-based decision making, ensuring that carbon savings were real, measurable, and auditable. This transparency underpinned GS8’s ability to communicate environmental performance to stakeholders.
Relevant Products and Services
5. A Model for Future Developments
This project sets a precedent for future housing schemes aiming to decarbonise their materials footprint. Holcim’s responsiveness and GS8’s vision for a low-carbon future show how supplier collaboration and innovation in mix design can bring scalable sustainability benefits.
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