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By Mark Lundegren

Plant-covered walls are a popular trend in architecture and design today, reflecting our natural need and desire to have living nature around us. But not all so-called living walls or vertical gardens are created alike. Because of this, understanding their basic variations can help us to design, build, or buy living walls more optimally and advantageously.

Owing to their two quite different basic designs – green walls and green facades – and the high number of potential variations on these designs, living walls should be viewed as an extremely flexible design tool. In practice, they can be employed: 1) with nearly any type of building, 2) as both interior and exterior walls, 3) with either edible or ornamental plants, and 4) on almost any budget.

Living Wall Softens The Lines Of A Mid-Rise Modernist Hotel (LivinSpaces)

Indeed, after their initial construction costs, many living walls will steadily pay for themselves through superior building and environmental performance, in addition to offering strong and ongoing visual and psychological appeal.

Green Walls & Green Facades

The two basic designs of living walls, green walls and green facades, have similarities and important differences (see Wikipedia Green Wall). Overall, each form of living wall can be defined as follows:

> Green walls – are structures that contain soil or another growing medium across their surface or volume, and are thus normally filled or interpenetrated by the root systems of the plants that grow on or in them.

> Green facades – are essentially vertical trellises or framework structures that support the branch systems of plants – ones planted in the ground or containers at the framework’s base, or in floating containers attached at regular intervals to the facade frame.

Given these differences in basic design – and in addition to climate, location, and usage considerations – green walls and green facades naturally lend themselves to different types of plants and uses.

In general, green walls will do better with plants that have shallow root structures and relatively compact overall shapes – such as mosses, ferns, and herbaceous plants, but potentially including vines – since there is typically limited room for both root and plant growth in green walls. By contrast, green facades favor hearty vines, bushes, and other branching and woody plants, including espaliered trees, that can grow robustly and at some distance from their soil source – and steadily spread to fill the facade framework. 

Whichever approach to creating a living wall is used, both green walls and green facades share many of the same features and benefits:

• Aesthetic appeal and design enhancement
• Positive emotions & psychological well-being
• Sound reduction & buffering
• Summer shading/reduced heat gain
• Summer evaporative cooling
• Winter insulation & wind barrier
• Air filtering & improved air quality
• Potential for edible & medicinal plants
• Potential for wildlife habitat

As you can see, when attentively designed, green walls and green facades offer many important aesthetic, ecological, and financial benefits. And as mentioned before, their ability to reduce building costs – via reduced needs for ornamentation and lowered energy use over time – can lead to positive economic returns and fully offset the initial costs of living wall construction.

Still, despite these common aspects of all living walls, there are significant practical differences between green walls and green facades, making each more suitable for different settings and applications. I’ll cover these differences in the next two sections.

Exploring Green Walls

As outlined in my definitions, green walls are designed structures that contain soil or another plant medium as in integral part of the wall structure. In addition to soil, plant media can include natural textiles, such as felt or coir fiber, and even plastic sheets and other materials in the case of fully hydroponic systems. The type of plant medium used will of course naturally impact green wall design requirements and constraints, including the amount of weight the wall must carry.

Green Walls Are Typically Either Modular or Hydroponic (Growing Green)

The diagram above (click to enlarge) summarizes the typical designs of green walls. As you can see, the modular approach holds containers or a matrix of soil, usually via a modular panel structure. This type of green wall is thus comparatively heavy, but is also often more resistant to variations in temperature, ranging weather conditions, and water and nutrient supply interruption.

By contrast, and as its name implies, the hydroponic approach to green walls uses no soil, instead employing either a non-soil medium in its place or no medium at all, making the wall much lighter. When no plant medium is used, this is normally accomplished by sandwiching plant roots in plastic or otherwise immersing them in a water-nutrient mix. In all green wall systems, however, nearly continuous plant watering and feeding is normally needed, and is typically provided via closed-loop irrigation systems that circulate water and essential plant nutrients.

When considering green wall systems, it is worth weighing the following factors:

• Generally more expensive and complex than green facades
• Can have significant building loads that must be addressed
• More flexible, especially for creative planting patterns
• Rapid in-filling of the wall system via high plant density
• Irrigation and feeding systems normally essential
• Shorter lifespan and require structure and plant upkeep
• Higher technology and resource use means lower sustainability

In general, and despite their added design and resource demands, when highly orchestrated living walls or controlled plant patterns are desired, green walls are the superior choice.

Examining Green Facades

Unlike green walls, green facades are framework structures that exist more independently of, or are not as integrated with, the soil or medium in which their plants grow. Instead, green facades are primarily designed to support, and encourage the growth and spreading, of their companion plants. With green facades, plants grow on, rather than in, the wall structure.

As mentioned before, green facades use soil (or potentially hydroponic pools) in the ground or containers beneath the facade framework, or in containers placed at set intervals along the facade frame. When plants are grown directly in the ground, or in ground-resting containers, load bearing requirements are often considerably reduced compared with modular green walls.

Green Facades Primarily Hold Plants Rather Than Soils Or Media  (Growing Green)

The diagram above (click to enlarge) summarizes three typical designs of green facades. The first simply involves self-clinging plants that grow from the ground and fix themselves to an existing wall. The second design adds an enabling frame attached to a supporting wall at the top and bottom, and perhaps intermediate points, of the frame structure, which holds and supports the branches of ground-rooted plants. The third design further adds periodic containers or planters – for example at each floor in a multi-story building – allowing for green facades of much greater heights than with systems exclusively using ground-rooted plants.

You will notice that the second green facade design uses a two-dimensional grid system to support plants, but three-dimensional or space-frame grids can be used as well. In all cases, facade grids can be made of welded or woven metal, metal tension cables, and also using wood and other materials for the frame structure. The grid design itself can be rectilinear, diagonal, and many other shapes – based on both practical and aesthetic considerations.

And although plants can be affixed directly or closely to supporting walls, green facade frameworks are often attached to bearing walls in ways that leave some distance between the facade and its supporting wall – for air circulation, plant health, and system durability – as shown in the second and third designs.

When evaluating green facade systems, it is worth considering the following factors:

• Generally cheaper and easier to build than green walls
• Often easier to retrofit green facades to existing walls
• Building loads are often much less than with green walls
• Less control of eventual plant patterns on wall
• Slower in-filling of wall due to lower plant density
• Irrigation systems may be simplified or eliminated
• Longer lifespan and often low structure and plant upkeep
• Less technology and resource use means higher sustainability

For these reasons, unless you seek highly composed or controlled plant patterns in a living wall, or require rapid plant in-filling, green facades are normally a superior choice.

Have A Wall? Go Green!

I hope this overview of living wall systems has been informative to you, and that it will inspire you to build a living wall near you. Green walls and green facades offer many important benefits, in addition to simply being beautiful, uplifting, and renaturalizing.

If you would like to learn more about living walls, we recommend Wikipedia Green Wall, Gergely Vizi’s thoughtful video on Living Walls, and GreenScreen’s in-depth overview of green facades (pdf) as good next steps.

As we discussed, living walls often can be built at a low cost – and even with the potential for positive financial returns – making them both economically and aesthetically attractive. Given this, I expect green walls and green facades to grow and grow, in popularity and organically, in the years ahead. Let me know what you think in the comments section below.

Mark Lundegren is the founder of ArchaNatura. 

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