I'm involved in the maintenance of an old northern Vermont church built in the 1860s. The church has a service only one Sunday per month during the winter. Some people are concerned that the plaster (split lath base) which was patched to remedy water damage from roof leaks, will be damaged if there is no heat in the building; they advocate heating the church to 40 degrees F all winter. Others point out that with no wall insulation or vapor barrier and large, single glazed windows, moisture migration from the heated air may damage the clapboards and paint and that condensation on the windows may cause damage to them. Historically, the church has been heated only on the days it is being used. Side issues are cost and carbon footprint. Would it be better to heat the building all winter or only when used?