BLUE TONGUE SKINKS

Hi, I live in a cold area and I currently have 3 100W ceramic heat emitters on the tank (4'x2'x2') and a space heater next to it and it still will only hit 80⁰F tops on the hot side, what can I do to make it warm enough for my little guy?

Post a picture of your cage and I'll offer a suggestion, if it is a glass tank with a screen top, cover most of the screen with foil to prevent heat escaping.