| Summary: | Moisture in roof constructions is currently a major concern in the building industry, especially in Sweden where the climate is often wet and the dry season short. In order to avoid these problems in the future there needs to be a greater understanding and focus on building techniques that prevent mold problems. Crucial to mold prevention is the vapor retarder, which is relied heavily upon in roof construction in order to prevent the airflow between indoor spaces and the construction itself. In most theoretical models this retarder is viewed as flawless, however this is often not the reality. The purpose of this study is to investigate the moisture and related mold problems associated with different degrees of perforation in the vapor retarder in two different types of roof constructions, a non-ventilated pitched roof and a traditional ventilated pitched roof. The constructions are located in Lund and Luleå and two different vapor retarders are tested, so there are four different constructions for each location: Ventilated inclined roof with glass wool slabs and Isover Vario KM Duplex UV (S.201) Ventilated inclined roof with glass wool slabs and Isover Vapor retarder (S201) Non-ventilated inclined roof with glass wool slabs and Isover Vario KM Duplex UV (S.204) Non-ventilated inclined roof with glass wool slabs and Isover Vapor retarder (S.204) Simulations have been made in the program WUFI Pro 5.1. Results from WUFI have been analyzed in a mold dosage model developed at Lunds Technical University. The results of simulations performed in this study show that the traditional ventilated pitched roof performs better than the non-ventilated pitched roof when a perforation exists in the vapor retarder. Generally the smallest of the studied perforations (d=5 mm per m^2 roof area) is acceptable in the ventilated pitched roof but larger holes lead to extensive mold growth. In the non-ventilated compact roof a hole in the vapor retarder cannot be accepted according to calculations in this study. The study also shows that ...
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