Vapour-pressure deficit the plant may dry out and die. For this reason the ideal range for VPD in a greenhouse is from 0.45 kPa to 1.25 kPa, ideally sitting at around 0.85 kPa. As a general rule, most plants grow well at VPDs of between 0.8 and 0.95 kPa. In ecology, it is the difference between the actual water vapour pressure and the saturation water vapour pressure at a particular temperature. Unlike relative humidity, vapour-pressure deficit has a simple nearly straight-line relationship to the rate of evapotranspiration and other measures of evaporation. To compute the VPD, we need the ambient (greenhouse) air
Nonresidential water use in the U.S. was 15,900 mgd. The amount purchased from public systems was reported to be 4,750 mgd in 1995 (or about 40 percent of total CII use). Based on the total floor space of 11,100 million square feet in manufacturing buildings in the U.S. and assuming average use of 215 g/ksf/d, the total use of publicly-supplied water by the CII manufacturing category in the U.S. would be about 2,400 mgd or about 20 percent of the total CII use. Nonresidential water use in the U.S. Nonresidential water use refers to all uses (and users) of publicly-supplied (municipal) water other than residential use.