Year: 2015
Type: conference-paper
Abstract: 1 Faculty of Engineering and Architecture of the University of Ghent (UGENT), Ghent, Belgium, [email protected] 2 Faculty of Engineering and Architecture of the University of Ghent (UGENT), Ghent, Belgium, [email protected] 3 Faculty of Engineering and Architecture of the University of Ghent (UGENT), Ghent, Belgium, [email protected] 4 Faculty of Engineering and Architecture of the University of Ghent (UGENT), Ghent, Belgium, [email protected] Compact flat roofs are more and more constructed in Belgium due to their limited thickness allowing slender roofs with high thermal performance. In this roof type the insulation layer is situated in between the wooden rafters with the roofing membrane directly above on a wooden support structure. Due to this composition the condensation plane is located at the support structure of the roofing membrane. Thus, an increased risk of degradation is present as compared to a typical flat roof system where the insulation is placed on top of the structure. Generally, to account for this a moisturedependent vapour retarder is used in combination with a hygroscopic capillary-active insulation material, typically cellulose. It remains unclear though how hygroscopic non-capillary active insulation materials influence the hygric response of the roof, what the influence of the initial moisture content and type of underlay is and what impact degradation of the roofing membrane has on the hygric stability of the construction over time. Therefore, a field test consisting of 4 compact roofs insulated with cellulose and 4 compact roofs with woodwool insulation, all covering a bathroom, was performed. The interior vapour barrier was varied between OSB sheeting, 2 moisture dependent vapour retarders and a PE barrier. Measurements were made both on the material properties and on the moisture content of the wooden support. Comparison with hygrothermal simulations using WUFI showed the importance of airtightness and achieving a specific density of the blown-in insulation material as well as avoiding air pockets around the wood pin sensors. Woodwool insulation was found to render a high risk on woodrot as compared to the safer spray-in-place polyurethane, mineral wool and blownin cellulose. The simulations clearly show the importance of avoiding water trapping during construction. Soiling of the roofing membrane was found to have a minor influence on the hygrothermal safety. On the contrary, degradation of the roofing membrane leading to leakage into the structure was found to lead to conditions favourable of rotting of the OSB sheeting.
Institution: Ghent University
Language: English
Subfield: Building and Construction
Field: Engineering
Domain: Physical Sciences
SDG: Climate action
Open Access status: green
OpenAlex ID: W2278105597