The Getty Conservation Institute and a team of engineers carried out a study with the use of computer simulations to give museum curators more precise guidelines on the energy requirements needed to maintain safe and acceptable levels of heat and humidity in museums. A number of cities was selected as simulation models according to criteria that would help refine the parameters of the study; other criteria applicable to the construction elements of the buildings used in the simulations are defined as well. The parametric analysis reported and detailed in numerous tables shows that with a modern heating, ventilating, and air-conditioning system, the least expensive relative humidity to maintain is 50% with significant cost increases occurring in trying for higher or lower levels; adjusting temperatures did not result in considerable savings, but the use of heat recovery chillers, one of several possible energy-saving strategies, led to important reductions in the costs of heating and humidification. -- AATA