A heating unit for use in heating pallets full of materials includes wall modules and a lid module. The modules include cover layers. Each module may include a heating component disposed between the cover layers and which is configured to convert electrical energy to heat energy and to distribute the heat energy. The heating component includes a heat generating element for converting electrical current to heat energy and a heat spreading element comprising carbon thermally coupled to the heat generating element. The modules may further include a thermal insulation layer. The modules may also include a receiving power connector electrically connected to the heat generating element. The modules may include a seam or hinge formed in a fashion that facilitates folding of the modules in a fashion which allows support members to support a module on an edge of the module.