Yeah, my shed is just a large metal box with no heat. If it gets too cold in there, I have a portable Coleman propane heater that I can place inside. The shed also has windows. So i can open them it it gets too hot. I've never lost a tree winterized in my shed.
My garage is insulated all around but I only use one side just for figs. The wife's car sits on the other side. The base station also has a freeze alert that flashes green when temps drop past 32 degrees. It's a pretty near device! It also has a built in usb to download data to my computer. Since I'm an IT guy, I like that!