Take a look at the sticky thread on the top of the husbandry page.

1) If you are using a glass tank you will need to block off the majority of the top. The sticky has a diagram. I use a slightly modified version that is a bit tighter around the lamp but also has a small opening on the opposite side. I think that it allows better flow because the heat lamp forces air upwards which also draws air in on the far side - a convection current.

Anyway, if you don't do this you will find it extremely difficult to get the overall temps up and maintian the humidity (esp if your air is at 39!!)

2) Convering a large portion of the glass is good for your snake and will also help insulate a bit.

I went to the craft store and got a few packages of 3/4" sticky-back velcro. I put a strip of the loop-side (softer side) all around the top and all around the bottom. Then I got a big roll of pressed cork from Walgreens and cut squares the size of the ends of the tank. On these I stuck hook-side velcro strips along the tops and bottom (matching the tank). So, basically I ended up with a system that allows me to easily control where and how much glass is exposed simply by adding, moving, or removing these squares. I found that they helped bring the temperature of those cool corners up a few degrees too. This isn't necessary and kind of expensive but it was a fun project. You can do other things to cover the glass.

3) Go to walgreens and get a mister. They sell some in the cosmetics area that work well. You can also get them where they sell garden supplies. Basically you will need to mist every day or two to pump the humidity back up. Over time it will come back down as the cage dries out.

I would check out the sticky, maybe try some of my suggestions, and then see where you stand. If you are still having trouble, then I would try a bigger bulb.

Cheers!