In many historic buildings, conservation heating has been used to control the RH in winter. Heat pumps are much more energy efficient than direct electric heating, so this technology may be adapted for climate control. Dehumidification has not been regarded as appropriate for historic buildings due to poor regulation, but recent development in electronic hygrostats makes this technology an attractive alternative. The annual energy consumption for both control strategies was calculated from statistical meteorological data for Denmark. The most energy efficient control strategy is determined by the U-value of the building, the air exchange rate and the volume. For large buildings conservation heating with heat pump technology seems to be the ...