How we delivered a net-zero canteen for Kew Gardens

Arboretum HQ, RBG Kew

How we delivered a net-zero canteen for Kew Gardens


BREEAM Rating Outstanding and net energy in use zero
Project cost £4.5m
Structural material is cross-laminated timber (CLT)

Working behind the scenes at the Royal Botanic Gardens Kew there is a small army of staff, in facilities ranging from world-class research labs to backyard maintenance areas. The arboretum headquarters is a new home for Kew’s tree specialists, delivered to meet the organisation’s exemplary environmental standards.

Kew is a UNESCO World Heritage Site, and its vision is to become climate positive by 2030. Taking on the project from RIBA Stage 4 onwards, environmental performance was therefore our main concern. How could we ensure that the building – which has a canteen and welfare spaces for the arboriculturists on the ground floor and offices and training rooms above – met the BREEAM Excellent standard set in the original brief?

The concept design by Lawray Architects proposed a cross-laminated timber (CLT) structure with some steelwork elements. We worked to optimise this in delivery, reducing the thickness of the timber structure to reduce the amount of steelwork needed, which in turn meant the size of the foundations could be reduced. We improved the building’s airtightness, meaning that the proposed mechanical ventilation could be taken out, and put the budget saved towards energy-producing photovoltaics for the roof. As a result, the building is net zero in use as well as reaching a higher BREEAM Outstanding rating.

To our surprise, we learned a lot about compost on this project. The building is next-door to Kew’s compost heap, one of the largest in Europe. As the plant matter and manure breaks down, methane and aerosols are given off, some of which are toxic. Despite this, we were able to naturally ventilate the building by adding automatic roof vents for fresh air, and collaborated with Kew on a management strategy for the heaps so aerosol emissions are reduced when the windows are open.