"Airflow is essential!" Ok-- but really, why?
 

I've read a bunch of articles on in and the best justification I can find is that not drying the plants and general environs promotes fungus, rot, etc.

Also, that it evens out the temps and promotes evaporative cooling.

This would mean, to me, that given enough airflow to dry things out, we're fine.

Is there anything more to it?

That's pretty much it.

How much air movement or air an orchid needs to its roots depends on the conditions of the native environment. Some orchids are more susceptible to issues because they come from environments that are breezy (i.e. Angraecums from Madagascar).

Root rot - Wikipedia

Too much air flow is not good either. Air flow must be matched with RH levels. The higher the Relative Humidity, the higher the air can/should be. I was running ~60% relative humidity in my grow chamber, yet my Phal. aerial roots were always drying out. I had a computer fan about 2 feet above the plants blowing what I thought was gentle air. I had no leaves moving including thin Onc. leaves. I should also state that there were 3 other fans moving air too.

I simply unplugged the lower fan, and the aerials dramatically improved. Plumped up, green tips, etc.

Here is a good AOS article about balancing RH and air flow. It really opened my eyes.


Humidity and Air Movement: The Importance of Humidity and Air Movement in Successful Orchid Culture

Joe

Air flow in the growing area ought to be gentle and tumbling. The idea is to prevent pockets of stagnant air.

If you're referring to air flow to the root system, that's essential, as most orchids do the majority of the respiratory gas exchange through their roots, rather than leaves, as is the case for terrestrial plants.

I noticed a real Improvement in my orchids when I added small fans and made additional ventilation holes in the pots. The air roots on them are no longer looking as shriveled as they did last year.

Agree completely.

There are plants that will tolerate less airflow and seem less susceptible to associated problems. As a guide (with many exceptions), I find thin-leaved orchids need more airflow, thick-leaved orchids tolerate less airflow, both will suffer if there is no airflow. In my indoor growing, they get what they need by being in an open room that has an air duct nearby. I have never fooled with special fans, though there is a ceiling fan in the room when it is needed.

If you have whole house cooling and heating, based on my experience, you'll be fine with the following adjustments. Humidity around 40% plus - a whole house humidifier is great. In addition I use humidifiers in my 2 grow rooms. I also leave the heating/aircon fan virtually 24/7. Hot air rises and cool air settles - the reason why basements are cooler and more humid.
I've never used any plug in or ceiling fans and have been ok. A house has a lot of natural air movement - pets/people and ... science...
The lower the ambient humidity, the faster the plant dries out and the more you have to water. Of course you don't want the plants to be waterlogged for weeks but if that is happening indoors then it's probable the environment is not pleasant for anything.

Right- so I've got my VPD computer-controlled from ~5-8 before it kicks in with more humidity.

Are you paying attention to your vpd range?

It's early, and I'm just starting my coffee, but what's VPD?