how can i judge infrared light

[Yness]

When I set up my tank i thought that a UTH would be enough for at night and my uv during the day...it is getting cooler and now i am worried bout night time temperatures...i have a brb and am wondering what strength of Infrared light to use (wattage) at night to help with the temp..i have a tank that is 1 foot (w) by 3 feet (l) by 1.5 feet (h).

Also i use repticarpet for substrate but am thinking of using newspaper....it seems to be all the rage...I am concerned about keeping it moist. Does the substrate have to be moist...my snake has taken to going under the carpet on the side that does not have the uth on it..is that normal for a brb....heh

I will be getting a lamp tomorrow....thanx
I was going to post a pic of my tank but i don't have any clear pics on my computer...i know i have one on a cd somewheare but cannot find it