Humidistat-controlled Heating and Ventilation Systems to Create Preservation Conditions in Historic Buildings in the Dutch Climate

In a marine temperate climate historic buildings that are equipped with thermostat-controlledheating systems show very low relative humidities (RH) during the heating season. This maylead to mechanical damage due to drying of hygroscopic materials like e.g. wood. Humidistatcontrolled systems are investigated using two different cases. Two top monuments of theNetherlands serve for the case study: Hunting Lodge St. Hubertus and Muiden Castle.The effectiveness of a humidistat-controlled heating system is investigated, both by simulation and by experiment. When using humidistat-controlled heating, the heating system is mainly used to maintain basic temperature levels during the heating season. During the humid seasons the heating system may be used to lower RH. Simulations are performed using Matlab Simulink. In the experimental setup a humidistat-controlled room is compared with a thermostat-controlled room. Simulation results show that humidistat-controlled heating is a good method to provide preservation conditions in historic buildings. Simulation results are validated by measurements. Though energy expenditure is significant lower, thermal comfort may decline.A humidistat-controlled ventilation system is investigated by making use of simulation. In historic buildings with high visitor numbers, high moisture and CO2-levels may occur. By selective ventilating with outdoor air, excessive moisture can be removed and low CO2-levels maintained. Preservation effects mainly occur by eliminating high RH by ventilating with air that has a lower specific humidity or by slightly heating the ventilation air. To maintain healthy environment conditions, control of the system on CO2-concentration is a priority.