Ventilator-heater-based climate control systems, designed to provide preservation environments for both buildings and their collections, were installed in two historic buildings in hot and humid regions. Relative humidity (RH) sensors located both inside and outside the buildings controlled the operation of the systems. Their environments were monitored before and after the installation and operation of the climate systems to evaluate their effectiveness. An RH of less than 75% was maintained. Dust depositions increased slightly, only as a result of air movement, since the supply air had been filtered. In one case, microbial activity was reduced significantly. The installation of the systems and the modifications to the buildings were very simple. The operation and costs of running the ventilators and heaters were documented during the study. -- SCMRE