The Beauty of Green façades
My love for climbing plants probably grew from one particular example: the ancient Wisteria in Pukekura Park. No matter how hot the day, or how busy the neighbouring cafe, standing beneath the canopy of this grand plant always brings a cool hush.
Regardless of how many photos I already have, a visit home is never complete without filling my phone with more, just in case I haven’t quite captured the right angle of her gnarled trunk (below). Now, on the other side of the world, I find particular joy in late spring each time I see the neighbour’s smaller version burst into bloom.
Safe to say I was easily sold on covering our own home with climbing plants. However, I was surprised by the large body of scientific research extolling the virtues of green façades, and just what an important factor they can be in the fight against the Urban Heat Island effect.
The 115 year old Wisteria trunk, in Pukekura Park, New Zealand. Photo: Alice Bezett
So what exactly are Green façades?
Simply put, a green façade is any wall, fence, or other vertical surface that has a layer of vegetation growing on or directly in front of it. This can be from climbing plants that are grown in the soil at the base of the wall, and either cling to the wall themselves (such as English Ivy), or are supported by trellis or support wires. The other method for creating a green façade is by incorporating plant boxes that ascend the wall, for example the stunning Bosco Verticale in Milan, below.
What does the science say?
Aesthetic value aside, it turns out that green façades make two major contributions to making our cities a better place:
Increased biodiversity
Natural cooling of our homes and streets
Rich Biodiversity
It’s not a big surprise that introducing more plants help animal life. As our cities have become larger and more petrified, animal life has often been pushed to the boundaries.
What may be surprising, however, is just how large the effect can be, when regreening a vertical space. Recent research comparing biodiversity found in different types of green façades (for full text see here) found that they hosted significantly more insects and bird life than bare walls, even for taller apartment buildings.
A powerful advantage here is that we can green a vertical space without needing to make large or expensive interventions, meaning that it’s very easy to make more home for nature, without needing to move the homes of people.
Blooming Wisteria climbing a building (image source)
Cooling our city
A green façade cools your home by creating a thick layer of vegetation that shades the wall. It also increases the humidity slightly, and the evaporation of this water cools the wall down further.
As mentioned in a previous blog, a man-made wall that is exposed to a large amount of sunlight during the day can warm quickly, and then release this heat both into the home and the surrounding air at night. A green façade can reduce the surface temperature by up to 30 degrees Celsius, corresponding to a decrease in room temperature of up to 2-3 degrees (see the section on green façades in this book). This is an enormous difference during summer, making our homes more liveable without the cost of air conditioning.
Taking action
So how can you put this knowledge into action?
The simplest and most cost effective way of creating a green façade is to use plants planted in the soil, and trained vertically on trellis or wire supports.
I personally prefer this to using self-clinging plants, as on certain surfaces plants such as Ivy can degrade the building material.
Not all trellis or wires are created equally - I recommend looking for more robust versions from a building store (look for rust-free steel), rather than the cheaper versions found in plant stores.
Additionally:
Green façades have the largest cooling effect on walls that face the sun for a large part of the day - focus on these walls first if cooling is your priority. The thicker the layer of vegetation, the greater the cooling effect is, so go big!
Choosing climbing plants that are native to your area will be best for local biodiversity, and using plants that have been grown free of pesticides is always best. Alternatively, asking a neighbour for a cutting of one of their plants is better both for your wallet and reduces waste!
Make sure to decide whether you’d like green all year round (choose evergreen plants such as Tuscan Jasmine), or just in summer (choose deciduous plants such as Clematis or Wisteria)
Clematis growing around a window. Image source
