Larry, I live in Pittsburgh, I run one ceramic heater in the truck on anything down to 25 degrees. I do not insulate anything. When it goes below 25 degrees, I run a second ceramic heater out the rear doors of the van. This works well for me. Also you can buy the thermometers from radio shack. Put the sensor on the floor of the truck, but the main unit in your house/office to monitor temps thru out winter. I buy new heaters each year. I remove any turbos ,upholstery tools, etc. each night after cleaning. The pain is plugging,unplugging all winter long. You get the hang of it real quick. Its a gotta do it thing. Ron