Variable thermal insulation

A transport vehicle comprising

• an interior;
• a plurality of wall panels enclosing the interior to define an exterior of the vehicle, wherein each of the wall panels comprises:
• an exterior wall;
• an interior wall separated from the exterior wall by a variable insulation gap occupied by an insulation medium;
• and
• a flow driver connected in fluid communication with the insulation medium,
• wherein:
• the flow driver is configured to selectively switch properties of the insulation medium in the variable insulation gap between a conduction mode and in an insulation mode;
• the insulation medium has a first effective thermal conductivity in the insulation mode, and
• a second effective thermal conductivity in the conduction mode;
• the first effective thermal conductively is lower than the second effective thermal conductivity;
• the insulation medium is a first fluid in the insulation mode, and is a second fluid in the conduction mode, wherein the flow driver is configured to swap the first fluid with the second fluid and vice versa to switch between the conduction and insulation modes;
• the first fluid is chemically different from the second fluid;
• and
• the first fluid is air and the second fluid is water or oil.