Investigating the performance of hempcrete as an option for retrofitting masonry buildings

Abstract: One fifth of the energy consumed by buildings in Sweden is by those built before 1945, many of them constructed from solid masonry walls. Improving their heating energy consumption is a challenge we must face in light of human’s impact on climate change as well as increasing energy costs. Improving thermal performance can be achieved with many insulating materials however the environmental impact of the materials themselves must also be considered as does the hygrothermal effect on the existing building structure. Hempcrete has been accredited with both environmental and hygrothermal benefits in both retrofitting and new build projects but as a relatively new material its properties are not entirely understood, consequently steady state calculations and simulations of heating energy use are proving to underestimate measured performance. The aim of this study was to evaluate the viability of hempcrete as an insulation material when retrofitting solid masonry walls to low energy standards with regards to moisture safety using industry standard software to simulate the results and a mathematical model to assess the mould risk. The Life Cycle Cost and Analysis was also calculated. Results show that hempcrete would be viable and perform very well environmentally for this application but there are questions over the predicted hygrothermal performance and consequently moisture safety due to the complexity of modelling the dynamic behaviour of hempcrete as it has shown in physical tests to perform better than expected.