Building retrofit is essential to deliver decarbonisation. But its implementation could leave a legacy of waste if end of life is not considered now. Here I consider the challenges and implications of embedding circularity into building retrofit.Buildings retrofits improve energy efficiency and are an essential component of global decarbonisation plans. However, whilst many retrofit techniques will reduce energy demand in the near future, their longevity is rarely considered. This risks a legacy of waste with high recurring embodied carbon, and buildings that cannot be easily further upgraded in decades to come. To avoid this, engineers, architects, designers and builders must start now to embed a circular economic (CE) approach into building retrofit.
Typical retrofitsRetrofits usually tackle two main components: the building fabric and building services. I will focus on domestic building fabric measures. These seek to improve the thermal efficiency of walls, windows and doors through installation of insulation, double or triple glazing, and insulated doors. In temperate climates, such as the UK, building engineers and designers typically focus on reducing heat loss from the building to reduce energy demand. As temperatures rise however, they should also be aware of the post-retrofit risk of overheating in summer months and should ensure sufficient ventilation is provided.The thermal performance of building fabric retrofits typically degrades over time. For example, organic, closed cell insulation materials such as expanded polystyrene, extruded polystyrene, polyurethane, and phenolic foam, leach their foaming gases over time, reducing their thermal performance 1 . Similarly double glazing will not indefinitely retain its thermal performance. Over time glazing seals fail, which allow fresh air into the air gap between the glazing panes. This reduces thermal efficiency and can result in condensation between the glazing panes.In both cases the degradation in performance could lead to the need for replacement of insulation or glazing to optimise buildings' thermal efficiency. The degradation in performance of glazing means that windows are typically replaced after 20-30 years. While the component materials (e.g. plastic frame and window glass) can be recycled, this requires energy and supply chains to 'take-back' the materials. Glazing replacement is more frequent as the condensation highlights the degradation. But in a future net zero world, we are likely to also seek to replace insulation more often to improve building energy efficiency.The value of applying circular economy principles CE aims to keep materials at the highest value possible. In the case of a building this means retention and retrofit (rather than demolition) for as long as possible. However, we also need to consider how to keep the components and materials that are used in retrofit at the highest value possible. This means rather than recycling the materials from a window, priority should be placed on remanufacturing the window in-situ. This rete...
