I think that the tendency of a phalaenopsis to grow aerial roots is more a matter of the need for more water & nutrient uptake and/or mechanical stability, than growing conditions, but the inverted temperature/humidity profile concerns me.
There are different chemical processes that go on within a plant in daylight and in the dark. All such processes are temperature rate-controlled to some extent, so your conditions might be suppressing the daytime one and accelerating the nighttime ones. Further, phalaenopsis are CAM plants, so their leaf stomata are only open at night, when the relative humidity is normally naturally higher, and the loss of water through the stomata is reduced. Depending upon just how low, your low humidity at night is, you might be risking excessive water loss.
Having stated all that, yet knowing that plants can be pretty adaptable, I recommend you simply not worry about it, but be observant of the plant, adjusting as needed.