Vanda orchids do not like stagnant air. They are used to growing at the top of trees in the jungle, where the wind is blowing hardest and light is plentiful (this is especially true for the Vanda Coerulea). Vandas are very susceptible to fungus, so it is important that air flow is given so that water evaporates from the roots and leaves.
I found that a heavy duty fan was needed to move the warm heater air around. A fan with PWM control is easier to work with for adjusting the speed. It also has a RPM signal that comes back to make sure that the fan is working properly. The fan will not make the leaves or roots sway much, if at all (may be an even stronger fan is needed?). One problem with this fan is that is will not turn off completely, but will spin slowly instead.
The fan should be turned off during watering, since it will cause the colder water on the roots to evaporate making them even colder (especially since the heater is turned off during watering). It would also blow water into the heater if it was left on during watering, just like a strong wind blowing the rain underneath an umbrella.
A humid air exhaust fan is mounted on the inside back of the polycarbonate top. It pushes humid air out, which lifts up a very lightweight plastic flap. I think I may just get rid of the flap, since it was meant to keep the humidity inside the enclosure, but there is so much humidity rising from the bottom water reservoir that the exhaust fan ends up being on much of the time.
Air will be drawn in through the vents below the front doors, which may be cold, or very cold on some days. If the heater is struggling to heat up the enclosure, it is better to turn off the exhaust fan (and the humidity control loop).