An LCA case study of vernacular architecture retrofitting in northern Italy with natural and bio-based materials

It is almost universally acknowledged that the building sector has multiple relevant impacts on the environment. Indeed, it is a major consumer of raw materials, but also of intermediate products and related services, such as transports; moreover, energy performance of buildings strongly influences the use of fossil fuels resources. Therefore, it is not surprising that production, transport and use of construction materials have a significant impact in terms of global climate change, non-renewable resources depletion and damages to human health and ecosystems. For these reasons, choosing the right construction products has a relevant role in reducing environmental impacts. Hemp is a raw material that has found wide acceptance in the building industry in recent years, thanks to its fast growth and the limited amount of fertilizers, water and energy necessary in the cultivation stage of the crop. In this work, we report the results of the environmental assessment of the retrofitting of a countryside dwelling relying widely on the use of hemp-based materials. The building is a typical example of the rural vernacular architecture of northern Italy, and its retrofitting was made using only natural and bio-based materials. The environmental profile of this intervention was compared with a hypothetical scenario of retrofitting with synthetic materials, adopting the Life Cycle Assessment (LCA) methodological framework as standardized by ISO 14040:2006 and ISO 14044:2006+A1:2018. The “cradle-to-gate” scenario was adopted, corresponding to stages A1-A5 of the European standard EN 15804:2012+A1:2013. The extent of lime carbonation in hempcrete was assessed via a detailed experimental analysis, and its role on the environmental performance of the retrofitting was included in the LCA analysis.