The National House Building Council (NHBC) has recently released new guidance regarding the ban on combustible materials in high rise residential buildings. It has been suggested as part of this new guidance that living walls may increase the risk of fire – it states: ‘Due to the nature of materials used in green walls, it is not considered that a green wall system can comply with the requirements.’
In parallel to this, emerging national and regional planning policies are increasingly calling for the maximisation of green infrastructure. Specifically, the draft New London Plan states that ‘development proposals should contribute to the greening of London by including urban greening as a fundamental element of site and building design, and by incorporating measures such as high-quality landscaping (including trees), green roofs, green walls…’.
Planning Authorities are following suit; the City of London for example are adopting the requirement for threshold Urban Greening Factor (UGF) scores outlined in the draft New London Plan. The issue is that green walls are often the only way for developments to maximise their UGF score (0.4 for residential and 0.3 for commercial) thus complying with said policy.
This therefore presents a puzzle: can new developments maximise the delivery of green infrastructure and comply with policy if living walls are non-compliant with fire regulations?
Time will tell how wide ranging the influence of NHBC’s guidance will be. Similar guidance on living roofs has suggested that biodiverse roofs can be designed to avoid fire risk; the Department for Communities and Local Government recommends living roofs be composed of a substrate layer with a minimum depth of 80mm and an organic matter content of less than 50%. Luckily, this reflects idealised approach to the design of living roofs anyway, with optimal depths and organic content percentage well beneath these thresholds.
Guidance is therefore required to clearly outline how living walls should be designed to comply with fire risk whilst maximising their environmental benefit and meeting policy.
Greengage would welcome thoughts and shared experience on this emerging topic. Contact Olivia Guindon should you wish to discuss maximising Urban Greening Factor on your project.