To help with ambient temps here, I also use an oil-filled space heater on a timer. It's whisper quiet, so great to run at night...which is mostly when its on. helps keep my ambients up above 75 at least, which is great for the corns and just acceptable for the BPs who have a UTH on each end of all their enclosures.

Insulating all racks, loose tubs, and especially tanks helps a lot as well, and I will often wrap baby blankets around enclosures in addition to permanent insulation on really cold winter nights. So far, so good.