No, it is not. Catalina didn't insulate any of its boxes. They were originally designed as "ice boxes" and folks added mostly Adler Barbour units to them. One of the first things a lot of skippers do is add insulation. Beware of spray foam, it can expand rapidly and break the box.
I've been sailing our C34 for 14 years, haven't gotten around to insulating the box. My weather kinda allows it, but I installed a much bigger house bank system so the load doesn't impact me too much. That's another way around the electrical draw.