Though during cold weather litter caking is typically caused by under ventilation, in some cases litter caking can be caused by localized over ventilation, more commonly know as leakage. Cold air entering through a crack in the side wall, loose fitting curtain/tunnel curtain, or fan shutter, quickly falls to the floor leading a cold spot in the house. The cold spot can lead to litter caking in a couple of different ways. First, since cold air has very little moisture-holding ability, very little... moisture is removed from the litter in the vicinity of the leakage. For instance, 1,000 cubic feet of 90oF air at 50% Rh can hold 17 ounces of water. If the cold air coming in is 40oF and 50% Rh it can only hold 3 ounces of water. Since the air can hold very little moisture, it can remove very little of the moisture the birds are constantly adding to the litter in the house.