Controlling ambient Temps in a rack and My tank

I built a 10 tub rack and I am almost done wiring the flex watt and getting it put together but I am having a rough time figuring out how to keep the temps on the cool side under control. I cant keep the room the rack will be in a constant 80 degrees, ESPECIALLY in the winter coming up. Granted I live in Miami, FL so the winter is THAT cold but the house can still get in the lower 70s/upper 60s at the coldest point. I have a herpstat and 11 inch flex watt for the hot side so thats easy as far as getting the right temps but what about the cool side where there is no flex watt?

Covering the rack? Aiming some heat bulbs at the front of it? What are some ways I can keep the other end a good temp. Will the flex watt on one side make a gradient that is sufficient?

Also In my 40 long tank I have a female ball. Right now I have a UTH under 1/4 of the tank hooked to a dimmer. When I point my temp gun at the thing layer of aspen shavings it reads 91 degrees over the mat while the cool side reads 76-77. The digital air temp reads 75-76 in the middle of the tank. She has been spending the days on the cool side of her hide and when I take her out she seems kind of cool to the touch. I hooked a dome lamp up to a dimmer today and with it barely on and after a whole the "cool side was also 90 on the the surface. What should I do. It seems like just the light barely on throws it too high. I want to get my rack up and running so I can put all the snakes there.

You might want to think about one of those oil filled radiant space heaters. They work real nice for me.

An infrared lamp really works my tank.

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Insulation will help if u can't get ur room temps high enough. And a ceramic heat emitter on top of the screen can help but u will have to adjust ways of keeping ur humidity up