A Botanical Passivhaus

Kew Gardens is set to build a pioneering plant-based Passivhaus Learning Centre. The proposed new Learning Centre at the Royal Botanic Gardens Kew is aiming for the Passivhaus Premium standard and to be an exemplar low carbon building, as part of Kew’s ambitious climate targets. Plant-based construction materials being used on the project include timber and mycelium insulation, derived from mushroom roots.

Kew Gardens Learning Centre, Image credit: HMY Architects

The Learning Centre, which has just had its pre-planning application submitted, aims to be an inspirational space for users of all ages and will include:

7 formal teaching spaces
office space for the Kew learning team
gallery space for exhibits and learning materials
space for learning in external and sheltered external areas.

Kew Gardens Learning Centre. Image credit: HMY Architects

Targeting the most advanced Passivhaus class, Passivhaus Premium, the building will generate more energy than it needs via renewable sources. Energy will come from PV solar arrays combined with air source heat pumps to provide the small amounts of additional heating required. The expected heating demand of the Centre will be less than 13W/m², based on early PHPP modelling. Mechanical ventilation with heat recovery will provide comfort and efficiency for the whole building.

Kew Gardens Learning Centre. Image credit: HMY Architects

Counting carbon

Kew’s recent ‘Manifesto for Change’ committed its sites to become carbon positive by 2030. As such, the brief for this project is aiming for Passivhaus Premium, BREEAM Outstanding and Whole Life Zero Carbon standards, with the embodied carbon of the building's materials and construction, as well as carbon in use, being paid back by the energy the building will create in a 50-year service life period.

Kew Gardens Learning Centre. Image credit: HMY Architects

Embodied Carbon

The proposed building will use the existing slab of the redundant building as the substrate for its ground floor insulated raft to save embodied carbon. This also helps prevent any impact on the tree root network and also provides an excellent thermal bridge-free foundation detail, with the building structure effectively floating above the cold ground.

Kew Gardens Learning Centre. Image credit: HMY Architects

The building will be formed from rammed earth, timber (with the timber cladding being grown on site), bricks with 90% recycled content and mycelium insulation, which combines the root structure of mushroom plants with waste products to form a bio-based, compostable, building material.