Abstract: The present invention encompasses a system and method for insulating an aircraft passenger cabin from ambient temperatures without the need for insulation blankets. Hot bleed air flowing through a network of fluid passageways is directed into sealed bays formed between the outer skin of the fuselage and the wall panels of the passenger cabin. As the hot bleed air rises through the sealed bays, it insulates the interior of the passenger cabin from the outside ambient temperatures. The outer skin of the aircraft acts as a heat exchanger by removing heat from the bleed air before it is introduced into the cabin. The bleed air maintains the cabin at a comfortable temperature without the need for air conditioning when the aircraft operates at high altitude.