I thought I might add a couple of pics of how I keep the humidity up. It simply consists of a container of water and two sheets of kitchen paper folded in half and one end placed into the water. I have used two here and if the humidity is far too high then I remove one sheet and reduce the length of the remaining sheet (simply add more of the sheet into the water) rather than using more ventilation thus losing heat. It worked for me with other plants so orchids should be no different.