GrainPoint Psychrometric Calc

It is 7am, the building is wet, and the only question is whether to open the windows. GrainPoint answers that one. Type the inside reading and the outside reading. GrainPoint compares them on GRAINS — the actual weight of water each holds — and tells you whether ventilating would dry the place out or make the job longer. THE MISTAKE IT EXISTS TO PREVENT Outside at 85°F and 50% has a lower relative humidity than inside at 75°F and 60%. It feels drier. It is not drier: it holds about twelve more grains per pound. Open the windows on that and you have just pumped water into a building you are trying to dry. GrainPoint names that case out loud when it happens, because every instinct says the opposite. It also refuses to decide when the two readings are within a few grains of each other. A field hygrometer is commonly ±3% RH, and pretending a two-grain difference is a decision would be false…