Green Walls provide many health and environmental benefits – improving air quality, reducing pollutants in run-off, reducing noise and providing a natural habitat for wildlife, to name but a few.
In summer, they also help to cool the air within and around masonry by providing shade, and by reflecting back some of the sun’s heat. And in winter, they can help to reduce wind chill, protecting masonry from rainfall and/or the effects of freeze/thaw cycles.
Crucially, they also trap warm air next to the building, saving significant amounts of energy – and so reducing heating bills!
How much energy could be saved in winter?
The University of Reading recently carried out some research to help quantify the energy savings that can be achieved by installing Green Walls. They used heated brick cuboids to compare brick walls covered with plants to ‘bare’ brick walls.
The images here show the heat lost through an un-covered brick wall (on the left) compared to one covered by plants (on the right). The research found that on average, 21% less energy was consumed by the plant-covered wall during the first winter of the test when the wall wasn’t even fully established (mean energy 4.3kWh compared to 5.4 kWh per week respectively). In the second winter, when the foliage was more established, a 37% average saving was recorded (3.7 kWh v 5.9 kWh per week).
The largest energy savings were associated with more extreme weather conditions – for example, strong wind and/or rain, when energy efficiency improved by up to 50%.
It is worth noting that loss of solar-gain (brought about by the plants providing shade), had no effect on the energy consumed until early-spring. In fact, the Green Wall-covered brickwork stayed warmer even on the winter days where there was notable sunshine. Obviously, many variables will affect the final amount of energy saving, including the type and density of planting, as well as the location and orientation of the building, so the design of the Green Wall and the choice of plants are important.
And the benefits aren’t confined to the winter…
In the summer, carefully designed Green Walls can also significantly reduce and even eliminate the need for air-conditioning in a building – research having found that they can keep wall temperatures below 24°C (the critical level required for human-health).
These image from the University of Reading’s research show that in mid-summer, a brick wall covered with flora is 7-13°C cooler than the uncovered brick wall.
It’s great to have some research to back up the claims that Green Walls not only look fantastic, but also deliver performance and financial benefits. If you’d like to find out more, click here to read a review of the research and an analysis of its findings by one of the authors, Dr Jane Taylor on our green-walls website, as well as access to a copy of the full research article ‘A Hedera green façade e Energy performance and saving under different maritime-temperate, winter weather conditions’.