Wooden churches are common in Norway. Very many of these churches are poorly insulated or not insulated at all. During the cold winters this leads to great seasonal variations in indoor climate, with extremely dry air in the winter. This has disastrous consequences for church inventory: the woodwork cracks, and the paint peels off. Five medieval wooden churches are being examined in detail with respect to climate by means of advanced computing equipment. Relative humidity and temperature are being measured outside and inside, at floor level, just under the roof, and by selected objects. At the same time measurements are being made of changes in dimension in the same objects. The purpose is to understand the total climate, the local climates, and the response time of the wood in relation to the climatic changes, so that practical measures can be implemented to improve conditions for building and inventory. -- AATA