A method and apparatus for supplying heat and humidity to gas filled spaces by the addition of water to a dehydrated material that releases heat upon exposure to water, exposing the hydrated material to dry contacting gas which results in loss of water from the hydrated material to the contacting gas, the contacting gas being heated and humidified by such exposure, and subsequent dispersal of the added heat and humidity to the gas filled space. This sequence also results in regeneration of the dehydrated material so that these steps may be repeated. By limiting the amount of water addition to the dehydrated material within a cycle of the process, less time and/or energy is required to regenerate the dehydrated material and finer control of resultant living space humidity may be possible.