Drafts are caused by an air pressure imbalance. As warmed air rises to the upper levels of the building, it creates a positive pressure and leaks out of the gaps and cracks in the building's envelope. At the same time a negative pressure is created at the lower levels actively sucking in outside air to replace what leaked out at the top. In the Northeast this replacement air is cold and dry in Wintertime and hot and humid in Summertime. We call the replacement air a "Draft" and it makes us uncomfortable and wastes energy. This natural air circulation is called the "Stack Effect", the taller the building and the stronger the temperature gradient from top to bottom the stronger the effect is. It's costing you money right now and Infrared show you where the gaps in the building are.!