I also grow in a terrarium, actually an enormous growing chamber the size of a shower stall. *[img]http://www.**********.com/iB_html312/non-cgi/emoticons/wink.gif[/img]
It sits next to a window in which I put a 4" diameter fan attached to a 4" diameter flexible duct tube. The fan blows cold air from outside the window, through the tube (which has a tube from a humidifier attched to it so that the incoming cold air is saturated with humidity) and into the terrarium at night.
During the day I shut the window so the temps heat up but I leave the fan on to keep the air movement going. In the hottest part of summer I run an Air Conditioner in the window and just set the intake fan in front of it so the air will still be cold at night. I try to keep the chamber 50*F at night but it does creep up to 60*F in June as summer approaches.

N. x Judith finn doesn't require true highland conditions of 50*F at night a bit warmer is alright and I have recently moved it to my intermediate chamber who's night temps are 60-65*F. After two months it has not appeared to seriously affect the plant, it continues to grow new leaves and and pitchers just fine, no deformities as in the lowland chamber. I do expect to loose the old pitchers eventually because there is a big difference between these two environments temperatures, air flow and lighting.