Retrofit Programmes Shouldn’t Get a Free Pass for Sustainability
Net zero carbon retrofits are all part of a sustainable future for the planet. If, for example, we want to phase out gas boilers and replace them with heat pumps, buildings will need to be much better insulated to maintain a comfortable temperature.
Drastically reduced energy consumption will also limit the investment needed in new electricity generating, storage and distribution infrastructure to meet peak demand without fossil fuels. All of this relies on better insulated homes. These are some of the reasons behind RIBA’s recent call for mass retrofitting of the UK’s interwar housing stock.
It’s also well-documented that decarbonising the existing built environment has a much lower carbon cost than demolishing and rebuilding. New buildings tend to come with high levels of embodied carbon if they are made predominantly of concrete, steel, blockwork or bricks.
A new building typically has embodied carbon levels equivalent to over 20 years’ worth of operational emissions. As the grid is progressively decarbonised, the relative ‘cost’ of embodied compared to operational carbon will increase.
Sustainable Retrofit Programmes
It’s estimated that 80% of the buildings here today will still be in use in 2050 and most will need retrofitting. There are many inherent sustainability benefits to retrofit programmes. But that doesn’t mean we can forget all about our own sustainability.
Retrofit materials and equipment come with an embodied carbon cost from raw materials, processing, manufacturing and transport.
Some insulating materials like straw bale, hempcrete and wool store carbon and have effectively negative embodied emissions. Blown-in fibreglass and cellulose insulation have lower carbon impacts than rigid polystyrene. These calculations need to be factored-in.
There may be sound technical reasons why some retrofits need to use insulation with a higher level of embodied carbon. But all of this should be openly accounted for. The concept of open book accounting should extend to embodied and operational carbon.
As we establish retrofit programmes we will have to remain conscious of where everything comes from and how it is produced. Careful supply chain management will be needed not just to ensure continuity but also to ensure there is proper stewardship and control.
Retrofits and sustainability go together naturally. But it’s important that we don’t take sustainability for granted.