Hygrothermal performance of a massive natural stone masonry wall insulated from the internal side with hemp concrete – field measurements in cold climate

Abstract

Improving of exterior walls in historic and traditional buildings is often only possible with interior thermal insulation. The actual structure and material properties of the existing exterior wall are usually the main unknown factors. Therefore, field measurements with small mock-ups are helpful before large-scale renovation. The current study analyses by field measurements the hygrothermal performance of internally insulated massive stone wall. Two different hemp concrete mixes were developed for the insulation. Temperature and humidity conditions were measured periodically over one year period. Results showed a very low drying rate of hemp concrete interior insulation. The external side of hemp concrete insulation will stay moist for a very long period. Temperature of coarse hemp concrete was slightly higher during the cold period. Wooden studs used to install hemp concrete will stay in moist areas for a long period. Temperature drop below 0 °C shows that interior insulation should be durable for freezing-thawing cycles. Drying out of constructional moisture is absolutely necessary for hygrothermal design. Before considering large-scale renovations, it is necessary to further assess the long term durability and performance of hemp concrete in a moist environment. The temperature increase on the interior surface could slightly improve indoor thermal comfort.