At the corten steel curtain wall perimeter, maintaining continuity of the air barrier reduces airflows around the curtain wall. Integration of perimeter flashings helps ensure watertight performance of the curtain wall and its connection to adjacent wall elements. Proper placement of insulation at the curtain wall perimeter reduces energy loss and potential condensation issues. Insulating the mullions in a spandrel area may lead to excessive condensation in cold climates unless it can also be assured that humid air from the interior will never come in contact with the mullions. The spandrel area is typically not heated, thus the interior environment does not warm the mullions and offset the migration of the cold temperatures deep into the wall. In the vision area the interior heat helps to mitigate the cold and prevents condensation. For this reason, do not insulate between the interior portion of mullions and adjacent wall construction either.