A system and method for a variable temperature zone (503, 504, 505, 506, 507) in a storage and retrieval system (1), wherein the storage and retrieval system comprises a framework structure (100) which includes a rail system (108) comprising a first set of parallel rails arranged to guide movement of a container handling vehicle (201, 301, 401) in a first direction (X) across the top of the framework structure, and a second set of parallel rails arranged perpendicular to the first set of rails to guide movement of the container handling vehicle in a second direction (Y) which is perpendicular to the first direction (X), the first and second sets of parallel rails dividing the rail system into a plurality of grid cells, the framework structure comprising upright members (102) defining storage columns (105) for storing containers (106) within the framework structure, wherein the storage and retrieval system comprises at least one container handling vehicle configured to operate on the rail system wherein the different temperature zones are separated by an insulated curtain (501) that can be lowered and raised from the roof and can be moved up and down the length and/or the width of the grid system, and storage containers stacked on top of each other to create an insulating wall in the grid system.