L-shaped bracket for securing insulation relative to a mullion or transom includes a side plate which defines a first major side of the L-shaped bracket and a flange which defines a second major side of the L-shaped bracket. The side plate defines at least one aperture configured to receive a fastener so as to facilitate attachment of the side plate to a side surface of the mullion or transom. A first receiving slot is disposed in the side plate and configured to receive a clip leg of a clip. The first receiving slot can be defined by a slot plate supported in spaced relation to a surface of the side plate. The clip is configured to engage the insulation.