Wärme‐ und Feuchtetransport in Holzbauelementen unter freier Bewitterung

Joščák, Matúš; Sonderegger, Walter; Niemz, Peter

doi:10.1002/bapi.201010035

Cited by 3 publications

(1 citation statement)

References 15 publications

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“…They are increasingly important in civil engineering. For example, novel woodbased wall constructions made of solid wood (such as cross laminated timber or wooden walls connected with dowels or nails) are currently being developed (Joščák et al 2010). For wood as an anisotropic and hygroscopic material, accurate knowledge of the moisture flux in and also between the principal anatomical directions is important for precise structuralphysical calculations and for numerical modelling.…”

Section: Introductionmentioning

confidence: 99%

Combined bound water and water vapour diffusion of Norway spruce and European beech in and between the principal anatomical directions

Sonderegger

Vecellio

Zwicker

et al. 2011

HFSG

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The combined bound water and water vapour diffusion of wood is of great interest in the field of building physics. Due to swelling stresses, the steady-state-determined diffusion coefficient clearly differs from the unsteady-state-determined diffusion coefficient. In this study, both diffusion coefficients and the water vapour resistance factor of Norway spruce (Picea abies wL.x Karst.) and European beech (Fagus sylvatica L.) were investigated for the principal anatomical directions (radial, tangential and longitudinal) and in 158 steps between these directions. The values were determined with the cup method as the basic principle. The unsteadystate-determined diffusion coefficient is, independent of the direction, about half that of the steady-state-determined diffusion coefficient. Both diffusion coefficients are about two to three times higher for spruce than for beech. They are up to 12 times higher in the longitudinal direction than perpendicular to the grain for spruce, and up to 15 times higher for beech. With increasing moisture content, the diffusion coefficients exponentially increase. The water vapour resistance factor shows converse values to the diffusion coefficients.

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Section: Introductionmentioning

confidence: 99%

Combined bound water and water vapour diffusion of Norway spruce and European beech in and between the principal anatomical directions

Sonderegger

Vecellio

Zwicker

et al. 2011

HFSG

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Vergleichende Untersuchungen zum Feuchte‐ und Wärmeverhalten unterschiedlicher Holzbauelemente

et al. 2011

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At the campus of the Fraunhofer Institute for Building Physics (IBP) in Holzkirchen/Germany comparative measurements of heat and moisture transfer in five different wood-based building elements were carried out (wood construction with slotted wood elements, solid wood construction connected with wooden dowels, new developed soft fibreboard brick construction, solid wood panel construction, wood frame construction with stacked wood elements). The elements were installed on the west side of the test building and examined during one year. The following physical quantities were measured: indoor climate, external and internal surface temperatures, temperatures in the boundary layers, heat flux through the internal surface of the constructions, relative humidity and moisture content. Furthermore, the measured data were used for validation of the simulation softwares WUFI®Pro and Delphin. During winter, the measured U-values (from unsteady-state values) were compared with steady-state calculated U-values. Both values were well coincident. Moreover, the simulation results achieved good agreement by using the thermal conductivity values measured at ETH Zurich, which were considerably lower than the standard values. Although, the four elements had been covered with a non rear-ventilated façade, no critical values of relative humidity were measured inside the constructions. The simulation results of relative humidity have partly shown large deviations from measured data by both simulation softwares

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Einfluss von Hohlräumen auf die Wärmeleitfähigkeit von ausgewählten Holzwerkstoffen für den Baueinsatz

Joščák¹,

Sonderegger

Niemz

et al. 2012

Bauphysik

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An ausgewählten Holzwerkstoffen (Buchenfurnier, MDF‐ und Spanplatten) wurde der Einfluss des Einbringens von Hohlräumen auf die Wärmeleitfähigkeit untersucht. Für die Versuche wurden die Platten in mehreren Lagen geschichtet (Lagendicke je nach Material 2,7 bis 5 mm) und die Aufbauten variiert, wobei Platten mit und ohne Hohlräume verwendet wurden. Um den Einfluss der Wärmestrahlung in den Hohlräumen zu untersuchen, wurden zusätzlich Aluminiumfolien (geringer Emissionsgrad) eingelegt. Es konnte festgestellt werden, dass durch das Einbringen von Hohlräumen (Volumenanteil ca. 46 %) eine Reduzierung der Wärmeleitfähigkeit um bis zu 51 % erreicht wird. Ein zusätzliches Einlegen von Aluminiumfolie quer zur Wärmestromrichtung reduziert die Wärmeleitfähigkeitswerte nochmals wesentlich (bis zu 64 %) aufgrund der stark reduzierten Wärmestrahlung in den Hohlräumen. Dies ist besonders ausgeprägt bei den Aufbauten mit größeren Hohlraumdicken. Um das Potential des Anbringens von Hohlräumen im Holzbauwesen zu nutzen, wurde ein Vorschlag für ein neues Produkt auf Holzbasis präsentiert.Influence of the air cavities on thermal conductivity of selected wood based materials and their application for building industry. On selected wood‐based materials (beech veneer, MDF and particle board), the influence of inserting air cavities on the thermal conductivity was investigated. For the tests, the particular boards (board thickness: 2.7 to 5 mm according to the material) were layered in multiple layers by varying the assemblies and using boards with and without cavities. Additionally, aluminium foils (low emissivity) were inserted to investigate the influence of heat radiation in the cavities. It can be stated that inserting air cavities (approximately 46 % of core material) results in a reduction of thermal conductivity up to 51 %. An additional insertion of aluminium foils perpendicular to the direction of heat flow reduces the thermal conductivity once more significantly (up to 64 %) due to a strong reduced heat radiation within the cavities. This is particularly pronounced in the constructions with larger air cavity thicknesses. Additionally, a proposal of a new product based on wood has been presented to develop the potential of inserting cavities for timber construction.

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Wärme‐ und Feuchtetransport in Holzbauelementen unter freier Bewitterung

Cited by 3 publications

References 15 publications

Combined bound water and water vapour diffusion of Norway spruce and European beech in and between the principal anatomical directions

Combined bound water and water vapour diffusion of Norway spruce and European beech in and between the principal anatomical directions

Vergleichende Untersuchungen zum Feuchte‐ und Wärmeverhalten unterschiedlicher Holzbauelemente

Einfluss von Hohlräumen auf die Wärmeleitfähigkeit von ausgewählten Holzwerkstoffen für den Baueinsatz

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