An active thermal insulation system is disclosed. The system utilizes a cool air source or ambient air below a threshold temperature in conjunction with a phase change material and/or conventional insulation. In a controlled manner, the cooled air or ambient air facilitates the transition of the phase change material from a substantially liquid state to a substantially solid state allowing the solid phase change material to absorb heat. Cooled air or ambient air may be directed to the phase change material via a gap or plenum capable of introducing the cooled air or ambient air adjacent to the phase change material. A fan, blower or air intake device may be used to direct ambient air to the gap or plenum.