The paper presents a study of the indoor climate of a monumental building with periodic high indoor moisture loads. Several scenarios of the past performance and new control classes are simulated and evaluated. The results include the influence of hygric inertia on the indoor climate and (de)humidification quantities of the HVAC system. It is concluded that: (1) The past indoor climate can be classified as ASHRAE control C with expected significant occurrences of dry (RH below 25%) and humid (RH above 80%) conditions; (2) ASHRAE control C is not suitable for the new hall. The climate control classification for the new hall ranges from B to AA.; (3) The demands on the HVAC system to facilitate pop concerts in the new hall are 40 kW heating power, between 100 and 200 kW cooling power, between 40 and 80 kW humidification power and 125 kW dehumidification power; (4) In case of control class AA, placing additional hygroscopic material has no significant effect. In case of control class B, the placing of additional moisture buffering material (5 air-volume-equivalents) does not decrease the (de)humidification power and it decreases the (de)humidification energy by 5%.