A study of the walls of a medieval church shows that porous, water absorbent materials such as lime
plaster and porous limestone, will provide effective short and medium term humidity buffering in a room
with about one third of an air change per hour. The church also has natural humidification. The source of
the water vapour is probably ground water evaporating from the saturated lower part of the wall. The porous
brick floor also contributes to the humdication. Architects can adapt some aspects of church architecture
to improve climate stability in museums.