Insulating loading bay, of the type aimed at loading and unloading trucks, having • an insulating shelter for the lateral and superior closing of a passage area between the loading box of a truck and an opening to have access to a building, • a fixed footbridge protruding from the opening to have access to the building to form said passage area; • a supporting-leveling and vertical guiding mechanism for supporting-leveling and vertical guiding the shelter in respect of said footbridge, said mechanism including ∘ vertical guides on which the shelter is assembled allowing the shelter vertical displacement, ∘ pulleys assembled on a shaft located in the upper part of the mechanism, and cables, tapes or belts running on said pulleys and secured by its opposed ends to the shelter and to counterweights vertically displaceable in respect to the vertical guides, said cables, tapes or belts transmitting the vertical movement of the shelter to the counterweights; • said shelter is configured in the form of an inverted "U"; characterized in that the insulating loading bay comprises: • a fixed extension protruding from the loading bay of the building integrating a fixed support, said fixed support supporting the mechanism for supporting-leveling and vertical guiding the shelter and the shelter; wherein • the mechanism further has some springs (10a, 10b) and abutments (11a, 11b) with capacity to regulate the pressure of said springs (10a, 10b) located in opposed sides of said fixed support; permitting the vertical displacement of the shelter in respect of said fixed footbridge, and the absorption of the vertical displacements transmitted by the truck to the shelter, and permitting the shelter to recover its original position when the truck leaves the loading bay. • an insulating shelter for the lateral and superior closing of a passage area between the loading box of a truck and an opening to have access to a building, • a fixed footbridge protruding from the opening to have access to the building to form said passage area; • a supporting-leveling and vertical guiding mechanism for supporting-leveling and vertical guiding the shelter in respect of said footbridge, said mechanism including ∘ vertical guides on which the shelter is assembled allowing the shelter vertical displacement, ∘ pulleys assembled on a shaft located in the upper part of the mechanism, and cables, tapes or belts running on said pulleys and secured by its opposed ends to the shelter and to counterweights vertically displaceable in respect to the vertical guides, said cables, tapes or belts transmitting the vertical movement of the shelter to the counterweights; ∘ vertical guides on which the shelter is assembled allowing the shelter vertical displacement, ∘ pulleys assembled on a shaft located in the upper part of the mechanism, and cables, tapes or belts running on said pulleys and secured by its opposed ends to the shelter and to counterweights vertically displaceable in respect to the vertical guides, said cables, tapes or belts transmitting the vertical movement of the shelter to the counterweights; • said shelter is configured in the form of an inverted "U"; • a fixed extension protruding from the loading bay of the building integrating a fixed support, said fixed support supporting the mechanism for supporting-leveling and vertical guiding the shelter and the shelter; wherein • the mechanism further has some springs (10a, 10b) and abutments (11a, 11b) with capacity to regulate the pressure of said springs (10a, 10b) located in opposed sides of said fixed support;