Richard Sabin, Managing Director at Biotecture, looks at why living walls at Castle Mill student accommodation at the University of Oxford provide benefits that go above and beyond the rainscreen cladding systems they replaced.
THE living wall installation at the University of Oxford's Castle Mill student accommodation block illustrates how fire rated living wall systems are an effective method of recladding some of the thousands of buildings in this country that are currently fitted with unsafe ACM cladding. A fire rated living wall was a prerequisite at Castle Mill because it replaced aluminium composite material (ACM) cladding on the upper storey of the building.
A total of five of our living walls were specified at Castle Mill to replace the existing cladding, complementing Oxford University’s Council decision to adopt an Environmental Sustainability Strategy1 to get to net zero carbon and biodiversity net gain by 2035.
Living walls make a positive contribution to this target because they introduce much needed biodiversity and living plants absorb carbon dioxide from the atmosphere. In addition, spending time around plants improves our health, well-being and productivity, a key benefit for student on campus. And green walls can also improve a building’s energy performance by keeping them cooler in summer, so reducing the need for air conditioning. The fact that this was an existing building meant that the architects were focussed on keeping the amount of rework to a minimum. This involved us identifying a practical method of fitting the living wall to the existing building’s substructure once the existing material had been removed.
Further complexity was added to site works because Castle Mill is located close to a Network Rail mainline, meaning representatives from the rail company had to be present whenever certain types of machinery were operated. To facilitate these requirements, we created method statements and carried out risk assessments prior to starting work. On top of this, Network Rail had established a fire route to the track close to where installation work would be carried out. This had to be always maintained as a clear route.
To meet the fire performance requirements, we were able to present data from an independent fire assessment showing that our BioPanel living wall system was suitable for replacing existing cladding at the Castle Mill accommodation block.
Another important factor in the success of this project was the technical designs and details created by our in-house team showing how the living wall would fit with the existing architecture, together with methods for fixing back to the steel frame in front of the building.
Careful selection of plant species helped reduce the visual impact, effectively camouflaging the upper storey of this building, hence avoiding major reworks in the building itself. The most striking aspect of the foliage is its ‘shaggy’ appearance, which is exactly the look that the architects were looking for; it creates a harmonious aesthetic against the branches of nearby trees.
However, the trees also create shaded areas on the living wall and, working with the architects, this guided our plant selection so that they will remain healthy in the long term. We installed around 530m2 of living wall at Castle Mill over the five locations, comprising around 32,000 plants. Five automatic irrigation systems were created to ensure the long-term health of the plants.
The University of Oxford was pleased with the outcome and subsequently commissioned us to carry out ongoing maintenance on the living walls.
