Hygrothermal performance of unfinished attics (ventilated roofs) - an experimental study

Ventilated roofs with an air space above the upper floor insulation inherently are more prone to moisture damage than conventional attic construction. This paper will describe a series of realistic field tests on different types of ventilated roofs in order to evaluate their hygrothermal performance. During the testing period wind washing, thermal performance and relative humidity in the cold roof, on the interior surface of the underlay, moisture of the rafters and amount of dew water were monitored. The room under the cathedral ceiling was air-conditioned. The amount of migrated warm air into the cold area of the roof was well defined and controlled. The influence of different underlays and ventilation strategies was studied. Investigations show that there are only very slight differences of the individual roof constructions especially in the climatic conditions to be reached in the attics.Yet, at times, the differences are principally only visually discernable