If you are living or working in an older building that’s as leaky as a sieve, you may be tempted to tear the whole thing down and start over again. If you are tempted; resist! Although providing a blanket solution for reducing energy consumption and the environmental impact of buildings is very much like giving a definitive answer to the question; ‘how long is a piece of string’, a new study shows that retrofitting existing structures has less of an environmental impact than rebuilding.
A report by Preservation Green Lab used a lifecycle assessment approach to calculate both the embodied and operational impacts of buildings to ascertain whether retrofitting or demolishing buildings and then replacing them with energy efficient structures would be more advantageous. The study also compared the impact of replacing existing structures and keeping your leaky old sieve building as is.
The best case scenario here would be to retrofit existing structures, but even keeping existing buildings as is would be better for short term environmental impacts than rebuilding.
The reasons behind this logic lie in the impending 2030 deadline for preventing climate change. Energy consumption and environmental impact must be reigned in if the worst effects of climate change are to be avoided. If preventing global warming takes precedence over other considerations, the years that rebuilds take to pay back the embodied carbon from construction is too high a price to pay. Pay back periods range from 10 to 80 years in the buildings covered in the study.
What this means is that every existing building should be left well alone, even if retrofits are not an option. New buildings can aim for high performance with merry abandon, but a more carbon-responsible approach would be to repurpose an existing building. Leading researcher on the project, Jason McLennan had this to say: “Existing building reuse is an incredibly important part of a strategy for energy reduction. It needs to be at the top of the list.”
Of course, reusing old buildings alone cannot effect enough carbon reduction and the study notes: “Reuse alone cannot fulfill the urgent task of reducing climate change emissions… Reuse and retrofitting for energy efficiency together offer the most significant emissions reductions.” Retrofitting then becomes the best choice for effecting carbon reduction levels required to meet the 2030 deadline.
Not all retrofits are created equal and, in order to effectively reduce carbon, materials and the extent of the retrofit must be chosen with care. Retrofitting, if not conducted responsibly, can be every bit as carbon-irresponsible as a rebuild. Here, the choice in materials is crucial to successful reductions in carbon. The embodied carbon footprint of the manufacture, transport and installation of retrofit materials and equipment must have a reasonably short pay-back period through operational efficiency in order to stay within acceptable carbon footprints.
The study is not definitive and, if anything, simply draws awareness to the need to take into account the embodied carbon of retrofits and rebuilds and to keep the 2030 carbon goals at the forefront of your mind when making construction decisions. Each case needs to be investigated thoroughly to ascertain the best course of action. Not all old buildings are worth keeping and not all new high performance buildings are worth building.