humidity

Looking at the cagesbydesign.com web site I'm guessing your cage measures 72"H x 96"L x 48"D. That's a lot of air to saturate using ground substrate alone. If you cage is in a room with AC then you are pretty much always going to have humidity issues, especially at this time of year. AC wrecks humidity levels. If your humidity is at 40% then I would try multiple things in concert (several of which have already been suggested).

1. I'm a big fan of cypress mulch so I would use a thick bed of that. Keep it nicely saturated (but not soaked). You will need to keep adding water to it as it dries out. Cyrpress mulch can look dry on top while still being pretty moist in the lower layers so stirring it up every now and then won't hurt either.
2. I would also place a large bowl of water over a belly heat source to further add moisture to the air.
3. Consider manually misting daily or splurging for a programmable misting system.
4. Minimize the number and size of air holes/vents.

You should also double-check the location of your humidity monitor as well as the quality of the monitor. Make sure that it's giving you good information.

Regards,

my cage is 4x2x2

Bulbs really suck the humidity out of the air, especially on a cage with a mesh top. Is the any way to switch over to UTH?

i have a sealed top and i make it where dome fit perfectly in the whole that i cut out and then useing a router bit i put a 3/16 lip for the lamp to sit on. the last cage i built that was 4x2x2 held humidity really good

http://i91.photobucket.com/albums/k3...c/IMG00177.jpg


vent on the top left corner (my hot spot) i have another vent on the lower right hand side (cool spot) this keeps fresh air in the cage.
Cause like you said Heat rises. on the cool side vent you can feel the air coming in and on the hot spot you can feel the air coming out of the cage and i have had great luck with humidity levels with one i built

http://i91.photobucket.com/albums/k3...c/IMG00179.jpg

Zombie&lemons
I was having the same problem with humidity a while back. The temperature outside had dropped pretty low and the heater was running nonstop. The humidity in my apartment dropped really low and I was having difficulty keeping the snakes humid enough. Someone here suggested a warm air humidifier to bring up the room humidity. If the room humidity at your place is less then say around 40%, you may want to try this. It has worked for me. Now when I add damp moss to the enclosures I actually can see a difference on the hygrometers. Hope this helps.