Project Outline

Set between a conservation wetlands area of Metropolitan Open Land and the pioneering BedZED eco-village, Hackbridge Primary School provides a playful and natural haven for students in the London Borough of Sutton.

The all timber building is a trailblazing example of sustainability, with the Passivhaus Plus design supporting the school’s achievement of becoming the first truly zero-carbon school in the UK.

Brief

The innovative design strategy was developed in collaboration with an ambitious client and experienced design team. As the UK’s first ‘sustainable suburb’, the London Borough of Sutton wanted an inspiring and environmentally conscious school to continue the legacy of the neighbouring BedZED eco-village.

The council required a new two form entry school to complement their existing Hackbridge Road site. Architype saw the unique site as a remarkable opportunity for the UK’s first truly zero carbon school, celebrating local ecology and enhancing biodiversity.

The sheltered landscape for learning supports the school’s nature-focused pedagogy, with the site providing a new gateway to unlock the wetland habitat beyond for the wider community.

Architype suggested Passivhaus Plus as a strategy to achieve zero carbon, and on completion it became the first education building to be designed to the progressive sustainable standard.

Designed as able to expand to a two-form entry school it actively generates more energy than it needs to run, thanks to its highly efficient design and strategy of low carbon technologies.

Design

Themes of flora, fauna, discovery and habitat are evident in every aspect of the design. Physical links to the outdoors – such as extensive glazing and natural textures – actively promote interaction with nature.

Sweet chestnut battens clad the school’s exterior, echoing the form of a nature retreat, and inside, Architype’s material palette include tactile and non-toxic materials to enhance health and wellbeing.

This focus on the physical environment of the space is another benefit of using the Passivhaus Plus standard. Classrooms are full of fresh air, well-lit with large amounts of glazing designed for both solar optimisation and connections into the landscape. Triple glazed composite timber and aluminium windows frame views out to the surrounding Site of Importance for Nature Conservation, with high performance qualities that thermally and acoustically insulate the space.

Materiality

Life cycle carbon studies informed the majority timber-based palette, favouring renewable, non-toxic components with low embodied carbon.

Textured details bring tactility to the interior space, with smooth glass screen and earth-toned cement boards that open out from the double height hall space. Corridors are clad with birch-faced plywood linings. Balustrades and furniture, together with softwood batten slatted ceilings, further express connections to nature, mirroring the pattern of the school’s exterior timber façade.

Elegant polished concrete floors made from 70% recycled GGBS concrete give a high-quality, welcoming entrance to the school, a design choice inspired by the multi award-winning Enterprise Centre. This, combined with the lightweight Larsen truss timber frame, allows the school’s form to sit comfortably on the ground via a shallow insulated raft foundation.

The timber is 21st century precision cut CNC, manufactured from a 3D model to ensure perfect alignment and spacing on the building. It gives a crisp modern quality more associated with bespoke furniture and contrasts joyously with the external courtyards where fallen trees have been carved by artists into seats and sculptures.

Community / pedagogy

Architype’s collaborative team established a consultation framework early in the design process to fully meet pedagogical needs and integrate indoor and outdoor learning. With focuses on internal layout and adjacencies, the team designed a solution that would provide both short and long-term flexibility to the learning spaces. This included removable partitions in classrooms and plans for an additional extension for future expansion.

Artistic touches embellish every corner of the school, from the perforated anodized aluminium artwork at the entrance to the charming window decorations, designed by children who visited the wetland site from the earliest stages. Coloured panels on the hall elevations were inspired by students’ leaf drawings. Dragonflies, herons and moth species that are found on the site find their home within the school and encourage a sense of exploration of nature.

Extensive landscaping enhances biodiversity and provides a diverse range of outdoor learning opportunities including a water run-off pond planted with native marginal species and plants which thrive in waterlogged conditions. Moths and butterflies are protected in the exterior landscape.

Sustainability

The school is truly revolutionary: the rigorous methodology of Passivhaus Plus enables exceptional performance alongside zero carbon technologies which lowers operational carbon to below zero. Designed in 2015, the school meets and will exceed RIBA’s 2030 operational energy targets as well as exceeding LETI’s 2020 embodied carbon targets. Embodied carbon, at 405kg/CO2/e/m2, is half the carbon use of a typical ‘business as usual’ building.

Hackbridge Primary School, with an A+ EPC rating, generates more energy than it uses, saving 94,184kg CO2e/year, and should export 14,800kWh energy to the grid every year. This means the school has no net demand for electricity and far exceeds the requirements of BREEAM.

The reduced heating demand is aided by a ground source heat pump and inter-seasonal store, which provides free heating and cooling, all year round. A cosy layer of Warmcell further supports the insulation of the building, made of low-carbon recycled newspaper.

The use of elevated frames for the photovoltaic tiles on the roof enables a bio-solar array, providing a range of environmental conditions to optimise biodiversity. Planted species include sedum, ferns and cowslip which can adapt to these lower light conditions.

The new building treads lightly on the site. Natural swales form part of the urban drainage strategy, with careful consideration given to the land’s wetland status, including permeable paving for water run-off. The zero-waste approach means all of the soil excavated during construction was used to create gentle grass mounds in the playgrounds, creating a natural green barrier.

The renewable materials inside and out reduce ecological and lifecycle carbon impact, with rainwater harvesting, bicycle and scooter storage reflecting the borough’s ambitious environmental One Planet Sutton aspirations. Plant and animal species like moths and butterflies were protected on the site.

Site and setting

The school is set on Metropolitan Open Land, a site of ecological importance but also a former sewage works, a landscape that was neglected for years. Due to this sensitivity, great care was taken in the architectural and landscaping strategy, with Architype working closely with experts and members of the GLA and council’s planning department to successfully achieve planning under ‘Very Special Circumstances’.

A key aim of the school was that it would open up this biodiverse site to the public, providing a community space to enjoy the unique species that live within the wetland. The school is designed with multi-functional accessibility in mind, for recreational use in evenings and weekends. Additionally, improvements have been made to the accessibility to the site with wider footpaths, which had previously prohibited visitors. The external design strategy, working with landscapers Churchman Thornhill Finch, echoed the natural theme by creating a jetty for wildlife watching in the pond and retained the majority of the tree belt alongside London Road as a visible and acoustic buffer.

As well the biodiversity considerations, the site had additional complexities including the remains of Beddington sewage works that left concrete structures under the school’s footprint

The proposals have been developed considering the future aspirations of the remaining land to be developed as an Ecology Park, as part of the Wandle Valley Regional Park, continuing the sustainable and nature-focused legacy that the London Borough of Sutton have pioneered.