don't forget you can't even follow vpd outdoor.
If the temperature and humidity are known, VPD can be calculated--and followed. What can't be done is control the weather. Control is the difference between growing outdoors and indoors. Outdoor growers can't control the weather. Indoor growers provide the weather. What's happening outdoors can certainly be measured, though.
VPD is something fairly new in the cannabis history, people have grown and enjoyed cannabis without having a clue about vpd for millennial.
People also haven't always known about temperature and humidity, other than what they could feel, and VPD is calculated using temperature and humidity. They're different measurements of the same environmental phenomena. Framing an argument in terms of millennia mustn't overlook the fact that measuring temperature and humidity is also relatively new. Farmers have always had "a clue" about growing conditions, however. We all know whether it's raining or dry, hot or cold.
cannabis can grow healthy and vigorous without you following precisely vpd
Of course it can. Then again, things can go wrong, too. Knowing why a grow went well or poorly can be helpful.
also controlling precisely vpd in a small tent could require a lot of effort and a lot more investement for very little gain than just dealing with the weather and the season indoor. it may depend in what room the tent is located in inside your house also.
If humidity and temperature are measured and controlled, VPD is also measured and controlled. It just might not be calculated.
The initial investment and complexity of small tents are roughly similar to larger tents relative to scale. Cost per unit of yield probably would vary by tent size, though, due to capital cost differences.
Small tents can be challenging because they're small, but it isn't environmental control that challenges me. My main problem with my small tents is finding space for the equipment, in particular the heater and the humidifier. Placement of circulation fans can also be a problem.
What happens inside a tent certainly can be affected by other things, including what Mother Nature is doing outside. That effect can soon convince an inside grower of the value of an environment controller. It did me. Few of us can constantly adjust our tent environment when something changes, but an environment controller can do that rapidly. So, the key to precisely controlling VPD, humidity or temperature when growing in a controlled environment is to have a controller do the work. When growing in artificial conditions, we replace nature. We provide the sun, the wind, the rain, the day and the night. So, my best advice is not to try to be the controller. Sure, there's an additional cost, but I wouldn't want to run a tent without one. I just don't have the time or energy to do what a controller can do.
@HerbalEdu - I respect you as a grower and value your usually excellent advice. I just can't agree with or even understand your opinions about VPD. It's a useful tool and is easy to use (once it's understood). I grow in small tents (2x2, 2x3 & 2x4) and it's the first thing I look at when I check my controllers.