So i grow in an open smallish room. So ive been controlling my room (in flower) vpd to 76f and 55% humidity and its spot on 1.4vpd. But i never knew you had to calculate the leaf temp! So i measured the leaves with my ir laser thermometer and they are between 3 to 4 degrees cooler than the room. So i added the leaf temp to a vpd chart and my previous 76f and 55%h is about 1vpd. I don't want to go above 55%h so my room temp has to be 85f to hit the 1.4vpd. Is this correct?
Billy the Mountain
Well-Known Member
You did it right, the leaf temperature is needed to correctly calculate vpd.
For the curious, using the simplified Tentens formula:
vpsat = .61078 * 10**((7.5*leaftemp)/(237.3+leaftemp))
vpair = .61078 * 10**((7.5*airtemp)/(237.3+airtemp)) * (humidity/100)
vpd = vpsat - vpair
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