Abstract: A folding curtain wall acts as a large door in an exterior wall of a building such as a garden centre greenhouse. The door includes upper and lower bi-fold panels which are hinged to one another about a horizontal axis. The upper panel is hinged to the wall of the building above the opening to be closed by the door. The door can be opened and closed by raising or lowering the lower panel from its bottom edge. In the open position, the panels are folded generally flat against one another in an overhead position above the opening and effectively provide an awning above the opening. In the closed position, the door panels adopt a flat configuration or an outwardly angled configuration. In the latter case, spaces at the sides of the door are closed by fixed panels that extend outwardly from the wall of the building.