Cath O’Driscoll
Retrofitting a ‘living wall’ to a 1970s masonry cavity walled building can reduce heat loss through the structure by over 30%, according to a new study (Building & Env., doi: 10.1016/j.buildenv.2021.108491).
The University of Plymouth’s Sustainable Earth Institute compared two west-facing walls, one of which was clad with mixed non-native plants. The cladding comprises a felt fabric sheet with pockets allowing for soil and planting, and includes an irrigation system.
Besides the reduction in heat loss, daytime temperatures within the newly covered section remained more stable than the area with exposed masonry, meaning less energy was required to heat it. Buildings are responsible for 17% of UK greenhouse gas emissions and space heating accounts for over 60% of all energy used in buildings. These new findings could be a game-changer in helping the UK achieve its net zero commitments, the researchers say.
‘Within England, approximately 57% of all buildings were built before 1964. While regulations have changed more recently to improve the thermal performance of new constructions, it is our existing buildings that require the most energy to heat and are a significant contributor to carbon emissions,’ says lead author Matthew Fox.
The thermal performance gains will be much greater on a poorly performing wall than an energy efficient structure, says Fox. ‘It’s easier to improve the U-value (thermal transmittance) of a wall from 1.1W/m2K to 0.7W/m2K, than it is to improve a wall from 0.2W/m2K to 0.15W/m2K. The more efficient your wall becomes, the smaller the improvements that can be made.’
‘Our research suggests living walls can provide significant energy savings to help reduce the carbon footprint of existing buildings. Further optimising these living wall systems is now needed to help maximise the environmental benefits and reduce some of the sustainability costs,’ added co-author Thomas Murphy.
Although the plants in the current study were non-native, there is ‘unexplored potential’ to explore native species, according to Murphy, who notes that the wall soon becomes invaded by native species. ‘This native floral potential – thermal properties and use within green walls – is something we will look to investigate in future research,’ he says.
Image Credit: UNIVERSITY OF PLYMOUTH
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