ITS from Stack Effect

	In a heated building, the indoor air is bouyant and applies pressure to the top of the envelope. Big holes in the ceiling allow huge amounts of warm air to escape.	The heating system delivers virtually all the warm air to the first floor.
	The exhaust from attic bypasses depressurizes the entire building. When the envelope is leaky, it drives the NPZ over the top of the living space. If the second floor has little or no heat supply, it will stratify into a continually cool zone.