Water Vapour Pressure

Water Vapour Pressure is more based on the fundamental physics and expresses the contribution (ie, the partial pressure) of water vapour to the total pressure of an air mix. For example, at a pressure of 1000 Pa (1kPa), the partial pressure of nitrogen may be 700 Pa, the partial pressure of Oxygen 200 Pa and the partial pressure of water vapour 99 Pa, and other gasses 1 Pa.  

This parameter is useful to evaluate moisture migration from one point in the building to another.