Most people never think about how a room warms up or cools down, but again it is more complex than most realize. Warmer air rises and cooler air sinks. Old southern homes were built with tall ceilings where the warmest air would rise up above the people. Old homes in the north were built with lower ceilings to keep the warm air at people level. Both are based on the fact that a room warms from the top down and cools from the bottom up. It changes temperature by way of stratification. The top of the room will always be warmer than the bottom. So, how does this happen? Most heat enters the cellar through the various surfaces (floor, ceiling, walls, door …etc.) Molecules of air which are in contact with a surface are warmed up, become lighter than the surrounding molecules and rise to the top of the cellar. These warmer molecules all gather at the top of the cellar making a warm layer against the ceiling. As more and more molecules are warmed and rise upward this warm layer grows down the room. Meanwhile the lower portion of the cellar, under the warm layer, remains at a very stable colder temperature. A thin “stratification” layer that moves down the room when the cooling unit is off and up when the unit is cooling separates the upper warm air layer and the lower cold air.