A method for changing a temperature of the interior volume of a thermally insulated space to a preset temperature and maintaining it at the preset temperature using two thermochemical systems which can be connected to an external energy source. The reactor of one of the systems is heated until fully regenerated, while the other system keeps the temperature at the preset temperature; when the reactor is fully regenerated, the system comprising the regenerated reactor is used to maintain the preset temperature and the reactor of the other system is heated to regenerate it as long as it is connected to the external energy source.