Keeping ambient temps up in a rack

How do you guys go about doing this? We set up our rack system recently and because it was warm, I didn't notice how badly they hold ambient temps. They have about a 7-inch long, 4-inch wide hot spot in a big adult sized drawer, the hot spot is at 90 always (herpstat pro) but when I use a tempgun anywhere other than the hot spot at night, it hangs around the 70's. The snakes tend not to sit on their hot spots either. This is gonna get way worse in the winter. What should I do?

I have this same issue with my 28qt rack so I have to heat the room their in to 75+ degrees at all times.
I use 11x12 inch pads under all of my 40qt tubs.

If there in a fairly small room then try to control the temp of the room itself. A rotating space heater with a digital thermostat should work fine. Ill probably have to do this come winter.

I live in Saranac Lake, NY where in the winter we are usually the coldest place in the nation, and living in an old house doesn't help. What I found helped was buying some 1" foam insulation board and putting it under the rack and cages and behind them. I have a stack of 3 4x2's and a 6 tub subadult rack from repti-racks and at first getting my temps set was a pain. Now I have the insulation board under the stack and behind it and its holding heat alot better. I also use the styrofoam they ship the cages with to put in between each cage so they each have their own temps. Without the styrofoam I found that each cage below the top one heated the above and would raise the temps about 10 degrees.

But Id deffinetly get some foam insulation. For me it has been key, and its the cheapest part of the stack. :D