Abstract
Traditional sloped turfed roofs are recommended to be ventilated to avoid moisture damage and ice building on roof eaves. The moisture content has been measured in the thermal insulation on three different holiday cottages with inverted compact sloped turfed roofs. The ice building and icicles on the roof on a continuous heated holiday cottage is studied through one winter. The design thermal conductivity of the insulation board used in inverted compact turfed roofs is determined. The risk of ice building on compact sloped turfed roofs is calculated. The calculation is done for continuous heated buildings with different outdoor temperatures and different snow depth through one winter season. The field study from Otta shows that conditions with stable low outdoor temperature results in a frozen turf layer through the winter season, even with a snow depth close to one meter on the roof. During such conditions the risk of ice building is very low. For inland regions with stable cold climate during the winter, like Karasjok, Røros and Lillehammer, the calculations show that the snow depth has to be higher than approximately 0.5 m to give noticeably ice building, even though the thermal insulation has a thickness of just 150 mm. With 300 mm thermal insulation, the risk of ice building is eliminated according to the calculations. In regions with average monthly mean temperatures a few degrees below zero, and a turf layer that is saturated with water and unfrozen when the snow starts falling, the calculations show that the risk of ice building is considerably higher. Such conditions combined with large snow falls will increase the risk of ice building. In such regions however mild weather might occur several times during the winter. Snow and ice will then melt and partly or fully disappear from the roof without any damaging ice building.