In a building, the time delay in the transmission of heat from an external to an internal surface. Plenum - A cavity through which air is moved. In some passive solar designs a plenum may be used to evenly distribute heat which otherwise would collect at a single point. The cavity can be used for supply air, return air, or can be switched to use for either. Chain Wall - A short wall or knee wall.
Underground temperatures can be very beneficial in balancing the thermal comfort of the home.
Normally we think more about the above ground temperatures and other climatic elements in designing a home for thermal comfort. The better design use and understanding of these elements produce a naturally comfortable home. An energy efficient design means that the mechanical system, which should be used for the extreme swings in climate, can be kept to a minimum size and should not have to be used as often as in a conventional house. Sky exposure will assure that there is heat gain during the day and heat loss at night. What is even more interesting is that the temperature at 15 feet below ground is even better.