Viv heating in a cool room

[Cam]

I see most rack and viv setups with the warm end heated by a UTH, Flexwatt or a RHP but then I think these are in snake rooms where the ambient is fairly high.

My question is in a cool (70-72F) ambient room (my living room), I'm thinking more than this might be required to manage the temperature inside a vivarium of any height (Thinking 3 wide, 3 tall, 2 deep or somesuch). Is this a typical problem, or something that most people manage by simply managing the amount of air circulation and insulation on the sides of the vivarium?

I'm wondering if I'm going to need a secondary source of heat to keep the general ambient inside the viv where I want it, with a UTH (or whatever) in one particular spot for thermoregulation.

Thoughts?