[AIVC, Air infiltration and ventilation glossary, 1992]:the transfer of energy to a space or to the air by the existence of a temperature gradient between the source and the space or air. This process may take different forms, i.e., conduction, convection or radiation.(see conduction; convection; heat ‘transfer; radiation)[EN 12792-2003, 202]:transfer of heat from one body or medium to another.