Freeze-thaw cycles are the most serious cause of roof tile deterioration; thus, it is important to know the temperature and moisture distributions in tile materials for protection against frost damage. This study focused on moisture boundary conditions for air layers under the tile. Temperature and humidity were measured using model structures with different types of roof tiles. The results showed that the temperatures around the roof were strongly influenced by solar and longwave radiation, and the humidity in the air layer was close to the outdoor. The ventilation rate between the outdoor and the air layer was estimated by numerical modelling based on the measured results. (C) 2015 The Authors. Published by Elsevier Ltd.