Thermal Transmittance in Roof–Wall Structural Junction Areas Insulated with a Hemp–Lime Mixture

Abstract

The junction between the roof and the external wall is a sensitive area within the building envelope; here, increased heat flow often takes place. In the case of partitions insulated with materials based on plant ingredients, thermal bridges are particularly dangerous due to the possibility of condensation and, consequently, mold. The present article analyzed the connection of the roof with the knee wall made of a hemp–lime composite and the ridge in terms of the occurrence of thermal bridges. The following factors that may affect heat transfer in the junction were taken into account: the location of the load-bearing wooden frame, the roof slope, and the presence of internal plaster in the junction. Two-dimensional heat transfer analysis was performed based on the finite element method using THERM 7.4 software. All of the studied thermal bridges had ψ values below 0.10 W/(m·K). Calculations of heat losses through a roof with different slopes were also presented, taking into account the considered thermal bridges. As the roof slope decreases, the heat flow through the roof decreases, despite the increasing value of the linear thermal transmittance. The share of the considered thermal bridges in the total heat loss from the roof reached up to 15%. To verify the obtained results, in further analysis, it would be necessary to calculate the impact of the roof–knee wall bridge variants on heat losses throughout the entire building.