Living Walls

Richard Whitfield - PhD, Manufacturing Engineering. Professor, USJ.

Living walls or vertical gardens are yet another, increasingly popular, way of “greening” urban indoor and outdoor spaces. Essentially, a living wall is a dense array of potted plants that are fixed to a wall, along with provision for automated watering (and feeding) and excess water collection. Some existing living walls are are several stories high, but most only occupy a few square meters of wall space.
There are several systems available for building living walls but they are not standardized. As you can appreciate the soil and plants in a living wall are quite heavy, and so you need a reasonably strong structure to support them. Nonetheless, many walls in Macau are strong enough to support substantial living walls. There are many, many boring blank outdoor walls around Macau that could be attractively transformed into living walls. There are also many boring indoor spaces, especially in public and commercial buildings, that could be brightedn up by creating attractive indoor living walls.
For most living walls you effectively have about 50mm of soil covering the supporting wall. This is more than enough for many flowers, grasses and similar ground cover plants. Very attractive visual effects can be created in living walls by mixing and matching different plant species. If suitable, slow growing, plants are chosen these patterned walls can be kept for a long time with little maintenance.
Plants always need regular watering, and so a good irrigation system is needed most living walls because they are often relatively inaccessible. A system of drip irrigation is usually the best so that there is very little excess water. Moreover, drip irrigation does not splash water into the air and so it is quite suitable for indoor spaces. Because the plants in living walls have limited root space they also need regular feeding, but this can be easily incorporated within the irrigation system – you just need to regularly mix liquid plant food in with the irrigation water.
Living walls can be remarkably clean and if suitably designed they require little maintenance. Once the soil has settled, and if drip irrigation is used, there is very little soil spillage or erosion. Also, as long as care is taken in choosing suitable plants there is little leaf shedding and trimming is only needed infrequently. Normal rainfall and wind will remove dust from external living walls. An air blower, like the ones used for sweeping leaves, can be periodically used with indoor living walls to remove dust and keep enerything clean.
I am hoping that at least 10% of the indoor wall space can be covered with living walls for the university's new campus in Ilha Verde. We are considering them for features at the ends of corridors, inside some meeting rooms and for inside toilets. We have already planned for window boxes on the ledges around the exterior of the buildings and so, effectively, about 20% of the exterior walls will also be “living”. We will have a large auditorium at the new campus which has some very large blank exterior walls. I am hoping that we can make these walls very attractive by mixing a large ceramic mural with living wall elements.
I am sure that the physical enrivonment of most of the schools in Macau could be greatly improved by the effective use of living walls.

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