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Last edited 27 Feb 2023

Living façade

[edit] Introduction

A living facade is a vertical surface incorporating vegetation into its structure or face to facilitate various aesthetic, environmental, social or economic functions and benefits. While research and studies on the subject are limited, it is thought that living facades could make a significant contribution to sustainability if properly integrated.

Also known as; living walls, vertical greenery systems, vertical gardens and vertical vegetated complex walls, they should not be confused with green walls (the process of allowing climbing plants such as ivy to scale a wall while being rooted in the ground).

[edit] Growing systems

Living facades can be grown and supported in two ways:

Without soil (hydroponically).
With soil.

Both of these methods have advantages and disadvantages and many of the benefits attributed to living facades will apply to both. However, soil-based walls tend to be confined to free-standing walls or gardens, and due to their weight, are rarely used in conjunction with buildings. Therefore, this article will deal mainly with hydroponic walls. Further broader information covering history and general use of hydroponics in buildings can be found in the article hydroponics and buildings.

[edit] Hydroponics

Plural noun [treated as singular] 'the process of growing plants in sand, gravel, or liquid, with added nutrients but without soil.' (Oxford English Dictionary)

The idea that vegetation can grow anywhere as long as it has water, light and nutrients is the basis of hydroponics and many living facade systems.

Vegetation on a living facade has to:

Have a medium to be grown on.
Be provided with enough water.
Be provided with enough nutrients.
Receive enough sunlight for photosynthesis.

Living facades depend on a mechanical system to provide water and nutrients. Many of these systems are complex, responding to temperature, direction of sunlight and other variables.

The rooting medium used can vary greatly depending on the preference of the living wall supplier and the needs of the plants. However, materials are generally chosen for their:

Water and nutrient-carrying capacity (porosity).
Ability for roots to take hold.
Weight.
Durability.

Common rooting media can include:

Felt.
Coco husk.
Rock wool.
Mineral wool.
Porous foam.
Wire mesh (with container for roots).

[edit] Structural systems

The structure of living facades varies between suppliers, however, there are three main structural systems, each with their own advantages and disadvantages:

[edit] Modular panel system

Panels of pre-planted vegetation are fitted to a support system that provides structure and a mechanical watering system. Pre-planting means that an instant green effect can be achieved upon completion. Composition of the modules will vary depending on the requirements of the vegetation, but will need to contain nutrients and material for the roots to hold. Soil can be used, but due to its weight it can only realistically be of use for small scale walls.

[edit] Synthetic felt

Pioneered by Patrick Blanc, this system uses synthetic felt as a base for vegetation, with water and nutrients provided mechanically. A metal frame is used for the structure, with a 10 mm PVC layer riveted to it and the felt stapled to this. The metal frame allows the structure to be attached to the facade allowing an air gap between the two layers which prevents vegetation from affecting the building structurally while aiding the thermal and acoustic properties of the facade.

The PVC layer prevents moisture escaping and provides rigidity to the entire structure. The polyamide felt layer consists of two overlapping sheets with various pockets that secure the plants. The choice of material is determined by its resistance to rotting and a high capillarity allowing water and nutrients to be distributed well. This facade has the benefit of only weighing 30 kg per metre squared.

[edit] Container and trellis

A series of containers house the plants with trellis in-between, allowing the vegetation to climb and create an uninterrupted face of vegetation. Water and nutrients can be provided mechanically with either a synthetic or soil based growing medium.

[edit] Positive effects

The majority of the positive effects of living facades are environmental, although aesthetic, social and economic benefits can also be identified.

[edit] Air quality

It has long been recognised that indoor plants can help improve the air quality in offices and an internal living wall can provide a similar effect and help rejuvenate 'sick' buildings. The plants absorb carbon dioxide and other particulates purifying the air.

The external air quality can also be improved by a living facade as it is able to absorb the carbon dioxide and pollutants from traffic. It has been shown that a living facade can have a major impact on the levels of nitrogen dioxide (NO2) and particulate matter (PM) in urban areas in which there are street canyons (where the height of buildings exceeds the distance between them). Street canyons cause the air to swirl and eddy around the vegetation enabling increased levels of particles to be absorbed.

A study carried out by Lancaster University found a reduction in street level concentrations of up to 40% for NO2 and 60% for particulate matter. With NO2 and particulate matter making up a large quantity of air pollutants, a reduction in concentrations of this magnitude would have a positive effect on air pollution in urban areas.

[edit] Thermal performance

The thermal effects of living facades are very similar to those of green roofs. ie, reduction in surface temperatures due to shading from vegetation, evapotranspiration and increased thermal mass. This can lead to a cooler internal climate and a reduction in urban heat island effect.

However, studies have shown that living facades may be more effective than green roofs in these areas.

[edit] Building performance

The surface temperatures and therefore the internal temperature of buildings can be affected by the presence of living walls and vegetation:

The vegetation shades the solid wall behind it, preventing solar gains.
Vegetation absorbs radiation therefore reducing reflection.
The increased thermal mass of the vegetation and substructure reduces the flow of temperature through the building skin.
Transpiration: the effect of water loss from vegetation by evaporation. Heat is carried away in the form of water vapour.
Protection from cold winds.

A 2010 study by the National University of Singapore found that the surface temperature of living walls was significantly reduced compared to a concrete control wall, with reductions of 6 to 10 degrees recorded. Analysis of the results concluded that shading and transpiration seemed to be the main contributors to this decrease.

In another study at the Chinese University of Hong Kong, decreases in both external and internal wall temperatures were found when a concrete wall was clad with vegetated cladding.

[edit] Urban Heat Islands

An Urban Heat Island is the localised increase of temperature in urban centres as opposed to surrounding rural areas due to a profusion of heat retaining surfaces. It is thought that the reduction in surface temperatures due to living facades could help reduce the temperatures in urban areas.

A computer model based analysis at the University of Cardiff found a significant reduction of the temperature in urban canyons when building envelopes were fully 'greened'. A similar conclusion was reached in a study by the University of Manchester, which found that an increase in green cover of 10% in urban areas could lead to a reduction in maximum temperatures.

[edit] Biodiversity

It is thought that living facades may contribute to an increase in biodiversity in urban areas by providing a habitat for insects and birds. Although specific testing on the biodiversity of living facades has not yet been thoroughly undertaken, there are examples of wildlife such as birds using living walls as their home. Any survey would have to acknowledge the potential disadvantages of increased biodiversity on a buildings facade.

[edit] Acoustic control

Vegetation is widely used to reduce the noise levels from busy roads or railway lines and it is thought that living walls may be used to control the acoustics of buildings. A study at the National University of Singapore found that living walls had a higher sound absorption coefficient than many standard building materials and that the noise reduction was also significant.

However, the study pointed out that these results varied greatly depending on the frequencies used, types of plant, percentage cover of wall and type of substrate. Further testing on actual buildings is needed to establish the true acoustic merits of living facades.

[edit] Aesthetics

Being in effect a vertical garden, the aesthetic qualities of a living facade are obvious and there are many examples where the primary objective is an aesthetic effect. Some of the visual benefits include:

Rejuveinating bland facades.
Softening of the urban landscape and allowing buildings to seem more 'natural'.
Changing aesthetics with season.
The softening and diffusion of light, which can enhance internal spaces when used in conjunction with glazing.

[edit] Social

The effects of vegetation in urban areas on wellbeing are well documented and studies have found that people view greenery as very important in these areas.

[edit] Economic

Although full cost analysis has yet to be carried out, it is possible that living facades could have a beneficial economic impact on buildings:

Reducing heating and air-conditioning costs.
Adding commercial value to the building.
Increased productivity.

[edit] Negative aspects

Living walls can require a high level of maintenance depending on the system chosen, and there have been documented problems with:

Root rot.
Plants dying.
The need for trimming.

[edit] Future / incorporation with sustainability

There are many other areas of sustainability that living walls have the potential to be integrated with:

Integration with air purification and ventilation, e.g. Queens University Biowall.
Vertical agriculture/farming: vegetables or fruit could be grown on living walls and then harvested, increasing the surface areas available for agriculture.
Water re-use: since living walls rely on mechanically supplied water, there is the opportunity to use grey water.

[edit] Code for Sustainable Homes and BREEAM

Due to living facade technology being quite new, at present there are no specific references in the sustainable code or BREEAM. However, living walls may be able to contribute towards other areas of the code, helping to earn credits.

Sustainability Code/BREEAM:

Combined with a rainwater harvest tank - Wat /W01
Native species planted – Eco 2 (ecological enhancement)/LE05
If significant area of property covered – Eco 4 (change of eco value)
Possible improvement of thermal performance – Ene1 (Dwelling Emission Rate)/E1

[edit] The need for more research

The lack of studies and research into living facades means that the true benefits and negative impacts are yet to be properly understood. Of the few studies available, most are either computer models, or testing carried out in controlled environments.

To truly understand the effects of living facades, long term testing needs to be carried out on buildings.

[edit] Related articles on Designing Buildings

[edit] External references

The Vertical Garden: A Scientific and Artistic approach, Patrick Blanc.
Thermal evaluation of vertical greenery systems for building walls, Wong, 2010.
Temperature decreases in an urban canyon due to green walls and green roofs in diverse climates, Alexandri and Jones, 2008.
Effectiveness of Green Infrastructure for Improvement of Air Quality in Urban Street Canyons, Pugh et. al, 2012.
Wildlife in our walls..., Biotecture Blog, 2012.
Acoustics evaluation of vertical greenery systems for building walls, Wong et. al., 2010.
Green Walls Column, George Irwin, 2012.
George Urwin on Living Walls, youtube, 2009.
Human Responses to Vegetation and Landscapes, Ulrich, 1985.
Living Walls - A way to green the built environment, Loh, 2008.
Living walls in indoor environments, Gunawardena and Steemers, 2019.
Thermal Performance of a Vegetated Cladding System, Cheng et. al, 2010.
BREEAM.

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Comments

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Living walls are in some way similar to green roofs. There are studies related to wind load on green walls. However, I cannot see any mentioning of wind load on living walls (or green walls). Will plants in a small pot be blown away by strong wind? Do we need to consider wind suction on living wall? Do we need to consider wind suction effect on the living wall fixing? it will be really useful if reference on this aspect is provided.

Thanks for your comment, we must have missed it. I agree these are all questions that would need to be raised. I assume it each case the answers would differ depending on location, local climate, future climate, the solutions selected etc which is why i imagine it doesn't include these specifics as they should come from the manufacturer, engineer of specialist designer.

You might find some useful guidance in the external links given or here: https://www.biotecture.uk.com/content/uploads/External_Cladding_Living_Walls_and_Fire_Safety_Best_Practice_Guide.pdf

although it is concerned with Fire safety in particular it may cover some of the points you raise by default here.