Joanna - I grow my orchids in a south-facing window, which can make it really hot right near the window, especially in the summer, and despite air conditioning. Humidity isn't the problem - that cools the plants down and you're right - the need that. What I've been told is the key to keeping the plants healthy is really good air movement. I have 4 small "muffin" fans directed in different ways, as well as a large fan pointed toward the ceiling. I also have 3 humidifiers going in order to keep the humidity around my orchids at between 60 and 70%. So, it may well be that you have all the right stuff - you just need more!