Abstract
In order to calculate amount of interstitial condensation in a building envelope, water vapour resistance of each layer is of importance. Once having it, 1D calculation according to ISO 13788 with monthly average vapour pressures can be applied. In EN 14509 sandwich panels are considered to be impermeable for water vapour, thus (according to the standard) water vapour cannot enter from outside and condensate in the panels. But it is not always true for real sandwich panels, because joints between neighbouring panels can cause non-neglecting water vapour bridges. Although in measurements of linear water vapour transmittance of the joints (Ψv) stationary boundary vapour pressures can be applied, the measurements can be long lasting. We shortened time needed to get Ψv performing simulations in Delphin 6.0. We simulated panels and steel sheets with joints using constant boundary vapour pressures and compared the results with the results of measurements on the equivalent systems. In systems under consideration a sealant in built-in-state, located at a joint of a sandwich panel, is a compressed EPDM tube. It is impossible to directly measure its effective μ according to ISO 12572. In the paper we study to which precision it is possible to determine it using measurements and simulations. Once having effective μ of the sealant (if all other necessary material parameters available) one can simulate condensation in envelopes including sandwich panels in 2D according to EN 15026 using hourly climatic data. Another goal of the study was determination of differences in resulting Ψv values when varying narrowest part of the gap dGAP at the joint in the panels without any sealant. Results confirm significant sensibility of Ψv to variations of dGAP.
Highlights
Significant proportion of nowadays industrial buildings is built from sandwich panels, which are composed from two steel sheets and thermal insulation in-between
In the paper we numerically studied stationary water vapour transmission through sandwich panels
We were interested in studying of sensibility of linear water vapour transmittance to narrowest gap width at the joint of two panels and to the shape and water vapour resistance of compressed EPDM sealants
Summary
Significant proportion of nowadays industrial buildings is built from sandwich panels, which are composed from two steel sheets and thermal insulation in-between. As for every building element, it is of great importance to check, whether water vapour can condense at the surface of sandwich panels or even in the panels. Surface condensation at inner surface in the neighbourhood of the joint of a cassette facade element, was numerically studied in [1] (cassette elements usually have larger thermal bridge than sandwich panels). Condensation near the joint is by far more probable than at the centre of the panel. With additional thermal insulation of the whole panel system at outer side, the possibility for water vapour condensation at inner surface was removed
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