A building material (50) comprises a plurality of transparent sheet layers (51,52) , adjacent transparent sheet layers (51,52) of which are disposed so as to have a gap (53) interposed therebetween and a vapor supply system (55) for supplying humidified air into the gap (53) between the adjacent transparent sheet layers (51,52). A building (10) including the above-mentioned building material (50). A method for controlling the indoor environment in a building (10) including the above-mentioned building material (50) comprises supplying humidified air into the gap (53) between adjacent transparent sheet layers (51,52) and generating dew condensation on a gap-side surface of the adjacent transparent sheet layers (51,52).
