How to minimize the water vapor inside the housing?

[rjsimp]

Humidity is the fuel and temperature difference is the spark. It takes both to create the condensation problem.

I leave my camera and housing in air conditioned room for a few hours before I put the two together and then I let the air conditioner blow directly into the housing as I put the camera in and close the lid.

My housing leaves me no room what so ever for desiccant packs and I have never had any condensation problems when I have followed this method.

I agree totally! IF the AC is working good where you are staying, it by its very nature removes humidity from the air making it very dry. So loading your camera in the room and sealing it there will make a huge difference. many times I have left the room in the morning and it is so humid outside that the entire outside of the camera is fogged. No big deal though as the inside is quite dry. A quick dunk in the hotel pool to make sure no bubbles and off to the dive boat.

I have never had a fogging issue and have rarely used packs inside my camera. I have used the packs when I had to crack open the camera on a dive boat and sure enough after the dive the pack is usually used up showing it was saturated with moisure just from the humidity in the air.

AC if you can, otherwise, a few packs in your camera that have NOT been exposed to humid air until the time you put them in.