Bio-Based Materials to Foster Efficient Retrofitting of the Existing Building Stock

In 2019, the European Commission started to introduce politics to decrease environmental impacts to achieve the goal of net-zero emissions by 2050. Within the many different policies, the European Green Deal and the New European Bauhaus are the ones that contain indications and guidelines for the member states to ensure that Europe becomes the first climate-neutral continent. Following this, to implement the Green Public Procurement (GPP), Italy instituted the Minimal Environmental Criteria (CAM) for public works, which help to identify better environmental design solutions by considering the whole life cycle of works, as well as other ‘traditional’ parameters, like costs and ease of execution. In Italy, mandatory CAM for public procurements is a first step in encouraging construction solutions and designing projects that pay attention to sustainability aspects. Indeed, in Italy, there is a huge number of constructions that were built between the post-World War II period and the 1970s, and these are inadequate if compared to contemporary requirements in terms of functionality and energy consumption. The intrinsic value of these buildings sometimes is neglected since they are not listed as heritage sites, but they are bearer of an indelible socio-cultural worth for the community, arose from the role they played to answer specific needs in periods of housing emergency and spread. Given their constructive systems, there is the need for substantial upgrading operations, able to preserve their value while answering today’s requirements. A possible strategy to achieve this, while keeping buildings’ value and improving the sustainability of the whole construction supply chain, is to enhance the use of renewable – and more specifically bio-based – materials. Starting from these assumptions, this contribution will first undertake an analysis of the state of the art on bio-based construction materials, with the aim of understanding which benefits there can be in their use compared to using traditional components. Second, the focus will be placed on cork and hemp, which are beginning to be more commonly used as thermal insulating materials. Afterwards, the possible criticalities of these materials will be analysed considering different aspects, for example, policies, costs, cultural aspects, technical prescriptions, and design features. Finally, a focus on studies and research that aim at further promoting cork and hemp use in retrofitting works by overcoming possible issues – costs, supply chain, availability – will be presented; this will help to better understand which aspects to focus on in future research on bio-based materials applied to the renovation of the existing building stock.