An architect’s guide to living walls

Architects and building designers are increasingly looking to green infrastructure to help mitigate the effects of climate change and reconnect urbanised populations with nature. Here, Richard Sabin, Managing Director at Biotecture, looks at why living walls are one of the best ways of achieving these goals.

The development of Biotecture’s revolutionary hydroponic living wall system 15 years ago helped change the perception of living walls from a novelty landscaping feature into a widely recognised building envelope solution, and they are becoming increasingly popular. Architect’s and clients are recognising that living walls are a space efficient way to bring buildings to life and help meet ambitious sustainability targets.

Urban uprising

Recent legislation has helped drive interest in living walls. The 2021 Environment Act will require all development schemes from Q4 2023 in England to deliver a mandatory 10% Biodiversity Net Gain which needs to be maintained for at least 30 years. And in London, The Greater London Authority (GLA) requires all large developments to meet an Urban Greening Factor target as a planning condition, ensuring that urban greening is considered early in the design process.

Living walls are a space saving way to meet these requirements, and other sustainability targets, without sacrificing valuable horizonal space.

A recent surge in demand for living walls came about because businesses are looking for better ways to impress customers, attract tenants and shoppers or encourage staff back to the office. Of course, there is more to the story than how the building looks or what legislation requires; plants have a powerful ability to reduce air pollution, mitigate the urban heat island effect and reduce noise, all whilst improving health and wellbeing of people.

According to the World Health Organisation (WHO), poor air quality in cities is linked to more than 5.5 million premature deaths annually, largely as a result of increased mortality from stroke, heart disease, chronic obstructive pulmonary disease, lung cancer and acute respiratory infections.

Plants in living walls help as part of the solution to this because during photosynthesis they absorb CO2 and other gases like oxides of sulphur and nitrogen (SO2 & NOx), ozone (O) and airborne ammonia (NH3) through their stomata. Plants also reduce air pollution by intercepting suspended particulate matters (SPM) and aerosols and retaining them on the leaf surface.

In 2011, we were commissioned to design, install, and maintain a living wall on the side of the Bakerloo Line Edgware Road Underground Station. We included fifteen plant species. Each of these were then tested at Imperial College for their ability to capture PM10s by the APRIL (Air Pollution Reduction In London) group. This and other more recent studies have informed the plant selection for our living walls to maximise the capture of pollutants. Targeted plants for targeted benefits. The living wall at Edgware Road celebrated its 10 year anniversary looking as good as the day it was installed.

Living wall as a rainscreen

Biotecture took the decision to develop BioPanelTM following discussions with architects and specifiers, who told us that their preference was for a platform that could be designed and installed like a rainscreen system. As a patented, modular hydroponic living wall it combines efficient water management with remote sensing technology.

The living wall system is fully tested in accordance with the requirements for the Centre for Window and Cladding Technology (CWCT) in 2015 and passed all tests for weathertightness, water resistance and wind resistance, confirming its full suitability and compliance for use as a cladding material for commercial and residential buildings.

A comprehensive independent engineering assessment with regards to reaction to fire confirms a system rating of B-s2,d0 which means the BioPanelTM living wall system can be, can be retrofitted as part of a façade refurbishment and incorporated within new buildings as the integral rainscreen cladding element. With an overall depth of around 80mm, and each panel weighing 18kg, the system provides a relatively lightweight and slimline profile. We often work closely with designers to provide consultancy services from the very start of the project and follow the process through the completion.

In terms of maintenance, living walls have a service life equivalent to many other cladding systems. That means, with a regular maintenance programme in place, they will flourish indefinitely. The technology used to maintain living walls has improved beyond recognition in recent years. For example, we use remote sensing irrigation systems and water is delivered directly to the root zone. This enables precision watering that uses a quarter of the water required on equivalent horizontal landscapes.

The way forward

We firmly believe that there will be more government incentives for urban greening in the future. However, regardless of legislation, we are finding that architects are wanting to incorporate greenery into their designs because they understand the benefit people get from reconnecting with nature. The fact living walls deliver health, economic, climate resilience, biodiversity and occupier wellbeing adds to the compelling reasons why they are right to do so. No other cladding material can provide these combined benefits.

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