While I only keep one avic, I stress that ventilation and humidity are key. You don't want to keep the air very stagnant inside, so make sure enclosures are well ventilated. However, they should not be very dry inside either, so mist the enclosure often, especially in winter where it is very dry anyways.
I have 4 Avic's. All of there enclosures have 10-20 holes or slits at the top, at the most with 2 or more isopods on the bottom. I have two i2 A. Metallica, a sub-a A. Versi. and a juvie A. Avic all with the same type of enclosure and the same amount of holes. the holes are the most 1/4" and the slits are made by a typical tweezer. seems to work well. i do however have the very bottom of the substrate wet and the top is dry, so there is enough humidity to cause condensation on the inside of the enclosure.
BIG waterdish and restricted ventilation to keep humidity up. My peat is DRY in ALL our Avicularia...Keeps molds and other nasties at bay pretty well. I mist once,MAYBE twice a week into their webs,other than that all misting them does is spike the humidity for a very short period of time.IMHO once they get large they handle lower humidity better than most think.Avicularia are wayyyy more hardy than most people tend to think.