Experimental study of thermal conductivity of cross-laminated timber panel narrow edges
Abstract
This study investigates the thermal conductivity of cross-laminated timber (CLT) samples made of Norway spruce when heat flow occurs parallel to the main plane of the panel. Due to the layered nature of CLT, heat transfer occurs both along and across the grain, depending on lamella orientation. The objective was to assess whether thermal conductivity varies with different proportions of end-grain in the heat flow path – relevant for construction elements such as building corners or foundation joints. Three CLT sample types were prepared with controlled end-grain proportions: Group 1 with 50.0%, Group 2 with 64.8% and Group 3 with 34.5%. Samples were conditioned at 20 °C and 65% relative humidity (RH). Thermal conductivity (𝜆) was measured using a HFM 436/3 device under steady-state conditions at 10°C, 20°C and 23 °C, with a 10°C temperature gradient. The results show a clear relationship between end-grain proportion and thermal conductivity. Higher end-grain content (63.8%) yielded higher 𝜆-values, while lower content (34.5%) reduced conductivity, indicating greater thermal resistance. This highlights the anisotropic nature of CLT and the need to consider grain direction in thermal calculations. Exposed panel edges with high end-grain content may cause localized heat loss and increase the risk of condensation, mould, or blue stain. Further modelling is needed to evaluate the impact on overall thermal performance and durability.
Reference
Edvins Grants; Uldis Gross; Viktorija Strausina. (2025). Experimental study of thermal conductivity of cross-laminated timber panel narrow edges. Engineering for Rural Development. https://doi.org/10.22616/erdev.2025.24.tf192
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