20.500.12556/DiRROS-24127 Experimental investigations of internal macro-scale convection in the loose-fill wood fiber insulation layer of a full-scale wall element With increasing restrictions on the energy efficiency of buildings, thicker insulation layers are installed in new and refurbished buildings to reduce heat losses. Previous studies have indicated that internal macro-scale convection cells can occur in thick porous insulation layers, decreasing the thermal performance of the envelope component. The focus of previous studies has been on horizontal insulation layers, most often composed of glass wool. Therefore, there is a lack of empirical data for loose-fill insulation and, in particular, bio-based materials, which have the potential of being more sustainable than conventional ones. The present investigation of this paper looks at the possibility of internal macro-scale convection inside loose-fill wood fiber insulation in a full-scale vertical wall element, with the modified Rayleigh number in the current investigation being between 20 and 45 and exhibiting internal convection in all cases. The experimental results show good agreement in terms of heat flux and temperature distribution with numerical simulations where the macro-scale convection is modelled explicitly. It also indicates that internal macro-scale convection can be modelled with existing building physics simulation tools, such as COMSOL. Finally, the internal macro-scale convection increases the effective U-value by up to 90 % for the highest temperature difference in steady-state conditions. This effect appears to diminish under dynamic boundary conditions, with a calculated effective U-value being within the uncertainty of the steady-state case with the lowest temperature difference, indicating that it might be less influential under real conditions. thermal performance internal convection performance gap insulation materials toplotna zmogljivost notranja konvekcija razlika v uspešnosti izolacijski materiali true false true Elsevier Angleški jezik Slovenski jezik © 2025 The Author(s) Neznano 2025-11-17 09:20:37 2025-11-17 09:34:50 2026-02-19 07:02:03 0000-00-00 00:00:00 2026 0 0 str. 1-14 [article no.] 116646 Vol. 350 Jan. 2026 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 2025-10-28 699.8 1872-6178 10.1016/j.enbuild.2025.116646 256038147 https://doi.org/10.1016/j.enbuild.2025.116646 0 4cfadb89-c38e-11f0-94a7-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=35896 RAZ_Veit_Martin_2026.pdf RAZ_Veit_Martin_2026.pdf 1 7B2025C1618A0819DD2E41987BD517EC 0cab162026576bf6d33ad5a2143525b78bd41ea0860b82226f94db7eb9fc0829 e77850cb-c38f-11f0-94a7-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=35897 Zavod za gradbeništvo Slovenije 0 0 0