Living walls

The air is cool and clear, climbing plants frame the windows of the 46th floor, and neighboring city dwellers seeing the totally greened façade feel a strong affinity with nature. This scenario may sound utopian, but it reflects the yearning of many town inhabitants for more greenery – and is already becoming reality in a number of urban construction projects.

Depending on the prevailing conditions, vertical gardens are capable of thriving without much water, as the KAFD Conference Center in Riyadh shows. The architects Skidmore, Owings & Merrill LLP (SOM) have designed the center as an architectural extension of the surrounding desert landscape. The building in the King Abdullah Financial District stands out not only with its faceted facade. Local desert plants on the outer walls and roof enhance the building’s futuristic appearance and underscore the oasis-like nature of the complex in the heart of the Saudi Arabian capital domina­t­ed by concrete and enclosed by desert.

The founders of the Canadian company Green over Grey have also considered the effects of plants on the climate in enclosed rooms and successfully applied the principle of the vertical garden indoors in their “living walls”. In an office building in Lévis, Canada, they have planted the world’s biggest greened interior wall with a height of 65 meters. The idea of cladding house facades, bridges or walls with plants is not in itself new, but requires special methods when implemented on a large scale. When ivy or Virginia creeper grows up a wall in the classic manner, the masonry always serves as the load-bearing element – a challenge in terms of long-term strength. However, this kind of greening is of no interest in any case for buildings more than eight stories high, as ivy’s growing height, like that of trees and other plants, is limited and rarely exceeds thirty meters.

The principle of the vertical garden is deceptively simple:
Using the method developed by Patrick Blanc, 1 centimeter thick PVC panels are riveted to a standing or hanging metal frame and covered with synthetic felt. Such constructions of any size can be attached to facades at any height. According to Blanc, a vertical garden inclusive of its frame weighs less than 30 kilograms per square meter. If a small gap is left between the plants and the wall of the building, the static layer of air in between acts as an insulator. If the vegetation grows on the wall itself, the plants and the substrate provide the insulation. The roots of the plants burrow into the felt, with nature serving as a model: Plants do not necessarily need earth, and many grow on tree bark, rocks or moss. What all plants have in common is their need for water and light, albeit to varying extents. The vertical garden is irrigated usually from the top, ideally with recycled waste water or rainwater. Plants are chosen not only for their visual properties, but also according to the light conditions on the building: north or south wall, strong sunlight or shade. The outcome is a suspended, self-contained eco-system that emits oxygen, cools the air in summer, insulates the building against the cold in winter, and brings nature a step closer to people in cities. I t creates habitats for wildlife, improves the microclimate, filters out noise and dust in the building’s immediate surroundings, and enhances biodiversity overall – particularly in urban environments. Greened facades are still regarded more as project art by the public and less as a functional design feature. But their potential is being increasingly recognized and exploited. The cities ass over the world continue to grow – above all upward because of shortage of space. If the resultant gigantic facade surfaces are converted into vertical gardens, natural greenery in the urban environment need be a utopian dream no longer.

CORPUS: Mr Poiraud, you describe the name green over grey to be programmatic – when did you start working with plants?

PATRICK POIRAUD: I have always been fascinated with plants, and my interest in living walls started when I was around eight years old after I first saw a vertical garden installation in Paris. My passion only grew from there. Green over Grey started officially as a business in 2008 but it was a few years before that when we started researching various technologies and studying in depth how plants grew vertically in nature.

CORPUS: What kind of challenges came up while working on “The Currents“?

PATRICK POIRAUD: The biggest challenge about ‘The Currents’ was the access as it is the tallest indoor vertical garden in the world. A living wall typically requires access for maintenance on a monthly basis so it is important that a proper system is devised from the beginning. This was accomplished by the general contractor installing a metal beam that a lift is attached to. Then every portion of the wall was accessible.

CORPUS: What is different working on an indoor living wall instead of an outdoor one?

PATRICK POIRAUD: Indoor walls are nice in the fact that you can control the environment, like lighting or temperature. However, in Canada especially the types of indoor or tropical plants that are available can be somewhat limited to a few hundred, whereas for outdoor walls there are literally thousands of plants to choose from. Outdoor walls are designed according to the exposure; a south facing wall will have completely different plants than a north facing wall.

CORPUS: How does a Living wall affect or change a room or do Living walls have effects for example for the room climate or the people surrounded by it? Are there any measurements or statistics concerning this topic?

PATRICK POIRAUD: An indoor wall will add a few percent of relative humidity to a room. Typically this is very beneficial to the dry environments that are found indoors. Sometimes you can find 25 percent of relative humidity, which is comparable to the Sahara Desert. Proven by the NASA is the fact that the plants also add oxygen and remove common indoor air pollutants. There have been studies that have proven that people living and working around plants are happier and more efficient. Also studies in hospitals have shown that patients with a view of greenery get better faster and take less medication than those without.

CORPUS: Could you describe for us what your clients are expecting from the Living walls? Do they express particular hopes in your work?

PATRICK POIRAUD: The main benefit to our clients we find is the overall improvement of aesthetics. Typically living walls are put in to beautify the space. Then there are of course the other benefits listed. Living walls are also not static and are constantly changing and growing which is quite different than a piece of art that always stays the same and might become outdated.

CORPUS: How is a living wall created? What does your design and construction process look like?

PATRICK POIRAUD: When designing a living wall we first discuss with the client their desires. This involves asking if they want a more colorful wall or one with just shades of green, abstract art or patches, flowers or fruit and which textures are preferred and what they like to be the overall depth – it can vary from a few centimeters to a meter or more. After that we come up with a design package, our planting map and finally install the materials, automatic irrigation and plants.

CORPUS: For your projects you are using eco friendly panels. What significance does sustainability have in your work?

PATRICK POIRAUD: Of course when we were developing our “green wall” system we wanted it to be as green as possible. There are other companies that use unsustainable, high energy consumption and even toxic materials. It was extremely important to us that we use 100% recycled and non-toxic materials. This is also expected from our clients and we feel we have perfected our product in this sense. Another part of the sustaina­bility aspect is bring nature back into urban environments. When designing our walls we aim to make them as biologically diverse as possible and include many native and locally adapted plants that will benefit the local fauna as well as the people that live there.

CORPUS: Mr Poiraud, many thanks for this interview.