My dogs got me up at 4am, your VPD comment has kept me up. So, before I go on, if lack of sleep makes me grumpy, which then gets my wife mad at me, and in response she burns down my plants, then please realize it’s all your fault.
There are dataloggers to monitor Vapor Pressure Deficit (VPD). With minimal programming skills you could make your own. There are a host of sensors available to measure the three parameters you need, RH, room temp, leaf surface temp. There are computer controlled relays available which allow you to control equipment for humidity and temperature. If hydroponics are used you might even be able to modify leaf temps by altering water temps. You can find charts on VPD that can let you derive control equipment max/min statements. (dimluxlighting.com under knowledge for charts, explanation, and info on their VPD datalogger.)
For this info to be useful, you need total environmental control of your grow area. You’ll need to either be able to respond to changing environment, or more simply force your environment to remain in a desired range. For example a room temp of 68, leaf temp 65, RH 38%, gives you a leaf VPD (LVPD) of 1.22. This is a safe range for flowering. Rather than monitor changing conditions, just force RT and RH to these points. To get this type of control you’ll need a well insulated area, be that growing area or the area the growing area is in. Probably R30 walls, R45 ceiling, R15 floor. To keep ongoing costs, ie electricity, reasonable, you’ll also need to seal seams, cracks, access points, and ducting. Now your system is closed so you’ll need CO2. Bottom line, costs to control this will get high. For commercial operations I’d guess environmental control, in the long run, is the most cost effective. For the home grower I don’t know. How much costs, on a per pound basis, is it worth?
Using myself as an example, I grow three indoor grows a year. If I took the steps necessary to control temperature I’ll have to build a really well insulated and sealed grow room, window AC, AC control unit. At a quick guess, $1500-2K for insulation, $1-2k to build room or to convert a shed. Then equipment costs for AC, humidity control, sensors, and so on. This excludes time and labor. Let’s say $3-5k gets it all done. You get an extra grow, healthier plants, less worry, better control, and possibly a better end product.
Far from intending to discourage you, my intent is to challenge you to go for it. I think for many the complexity and costs make this too daunting. Personally, I’m an idiot control freak. I like the concept of using info, like VPD, to allow me to maintain optimal growing environments. But I’m rebuilding my house so my barn is full of household crap. Soon as I barn room available, a woodshop, a walk in cooler, and an environmentally controlled grow room are on the list. If, a young intrepid intelligent trendsetter, for example, such as yourself, would embark on this journey, while carefully documenting success, failure, costs, changes in energy demand, then an old idiot control freak could save time, money, and effort. A great win for me and a valuable learning experience for you. Such a deal.
