Luckily, there is one more measure that can greatly lower the operational carbon footprint of existing buildings: improving the insulation.
Many older buildings have inadequate thermal insulating solutions or none at all. In turn, poor insulation translates into higher demand for heating in the winter and cooling in the summer, thus making the building more energy-intensive. Upgrading the building’s envelope materials to ones with lower thermal conductivity can significantly lower the energy demand. Ensuring proper insulation is the retrofitting option with the biggest impact on the overall carbon weight of a building.
But there is one crucial point that has to be considered in this step. While substituting the insulating materials, it is essential that their embodied carbon is as low as possible. Insulation materials are ranked as the third most polluting among construction materials. Using heavily polluting insulating materials such as polystyrene or other fossil-based materials would only partially address the environmental concerns for the building. In fact, using materials with high embodied carbon could entirely negate the benefits of reducing the operational carbon footprint of the building.
It is in such applications that bio-based materials shine. They have high R and U-values, can be sourced locally, and have low (if not negative) upfront carbon. Moreover, they are generally free of dangerous chemicals making them perfect even for indoor applications. Some examples are eelgrass panels, hempcrete slabs, compressed straw bales, and insulating blocks obtained from mycelium, the root structure of mushrooms. These materials offer specifications on par or even better than more traditional insulating materials. For a closer look at some of these bio-based options, you can read our previous article here.
Beyond environmental benefits, retrofitting also presents a compelling economic opportunity. For starters, the improved energy efficiency of a building can lead to substantial cost savings over time. Furthermore, thanks to the European Taxonomy, reducing the carbon footprint of an existing building can open up funding avenues. So then, why are investments in energy efficiency in buildings falling, and why are the rates of retrofitting so low?
Despite the recent push at the European level for such measures through initiatives such as the Renovation Wave, retrofitting is still not that popular. A lot of the economic incentives promised to companies and privates are left up to individual European countries, leading to mixed successes. Bio-based materials are still not widespread due to several reasons, including lack of awareness, higher upfront costs and market penetration.
And yet, the retrofitting dilemma is going to be one of the most pressing issues regarding the built environment. By 2040 it is estimated that approximately two thirds of the global building stock will consist of buildings already standing today. If our climate goals require the built environment to reach net zero emissions in the next three decades retrofitting will have to become a standard practice, alongside easier methods to assess the embodied carbon of the materials employed.