Mulling system for plural fenestration assemblies with matching thermally broken joining plates that have rotated and engaged arrangement across mulling axis

1. A mulling system for a plurality of fenestration units comprising:

a first joining plate that extends longitudinally along a mulling axis, the first joining plate configured to attach to a first outer edge of a first fenestration unit, the first joining plate including a first alignment fin configured to be received in a first groove of the first fenestration unit, the first joining plate including a first plate member, a second plate member, and a first thermal breaker that extend longitudinally along the mulling axis with the first thermal breaker attaching the first and second plate members;

a second joining plate that extends longitudinally along the mulling axis, the second joining plate configured to attach to a second outer edge of a second fenestration unit, the second joining plate including a second alignment fin configured to be received in a second groove of the second fenestration unit, the second joining plate including a third plate member, a fourth plate member, and a second thermal breaker that extend longitudinally along the mulling axis with the second thermal breaker attaching the third and fourth plate members;

the second joining plate configured to attach to the first joining plate to join together the first fenestration unit and the second fenestration unit with the mulling axis extending between the first joining plate and the second joining plate;

the first joining plate substantially matching the second joining plate to define a corresponding rotated and engaged arrangement of the first joining plate and the second joining plate across the mulling axis;

wherein, in the rotated and engaged arrangement, the first thermal breaker aligns with and overlaps the first alignment fin along a first transverse axis extending perpendicular to the mulling axis from one side thereof; and

wherein, in the rotated and engaged arrangement, the second thermal breaker aligns with and overlaps the second alignment fin along a second transverse axis extending perpendicular to the mulling axis from an opposite side thereof.

2. The mulling system of claim 1 , wherein the rotated and engaged arrangement includes the first joining plate defines a one-hundred-eighty degree rotation of the second joining plate with respect to the mulling axis in the corresponding arrangement.

3. The mulling system of claim 2 , wherein the first joining plate includes a first hook and a first flange disposed on opposite edges thereof;

wherein the second joining plate includes a second hook and a second flange disposed on opposite edges thereof; and

wherein the first hook is configured to receive the second flange and the second hook is configured to receive the first flange to attach the first joining plate and the second joining plate.

4. The mulling system of claim 3 , further comprising a fastener configured to extend through the first hook to be partly received between the first joining plate and the second flange.

5. The mulling system of claim 1 , wherein, in the rotated and engaged arrangement, the first joining plate and the second joining plate overlap with the first thermal breaker overlapping second thermal breaker.

6. The mulling system of claim 5 , wherein, in the rotated and engaged arrangement, the first thermal breaker defines a first width and the second thermal breaker defines a second width, the first width defined between the first plate member and the second plate member, the second width defined between the third plate member and the fourth plate member; and

wherein the first joining plate overlaps the second joining plate along a majority of the first width of the first thermal breaker.

7. The mulling system of claim 1 , wherein the first plate member, the second plate member, the third plate member, and the fourth plate member are made of a metallic material, and the first thermal breaker and the second thermal breaker have lower thermal conductivity than the first, second, third, and fourth plate members.

8. The mulling system of claim 1 , wherein the first joining plate includes a first hook and a first flange disposed on opposite edges thereof;

wherein the second joining plate includes a second hook and a second flange disposed on opposite edges thereof;

wherein the first hook is configured to receive the second flange and the second hook is configured to receive the first flange to attach the first joining plate and the second joining plate; and

wherein at least one of the first hook and the second hook includes a lip, the lip configured to support a covering member configured to extend between the first fenestration unit and the second fenestration unit to cover the lip.

9. The mulling system of claim 1 , further comprising an end plug configured to be received between the first fenestration unit and the second fenestration unit at corresponding ends of the first joining plate and the second joining plate.

10. A mulling system for a plurality of fenestration units comprising:

a first joining plate that extends longitudinally along a mulling axis, the first joining plate configured to attach to a first outer edge of a first fenestration unit, the first joining plate including a first alignment fin configured to be received in a first groove of the first fenestration unit, the first joining plate including a first plate member, a second plate member, and a first thermal breaker that extend longitudinally along the mulling axis with the first thermal breaker attaching the first and second plate members;

a second joining plate that extends longitudinally along the mulling axis, the second joining plate configured to attach to a second outer edge of a second fenestration unit, the second joining plate including a second alignment fin configured to be received in a second groove of the second fenestration unit, the second joining plate including a third plate member, a fourth plate member, and a second thermal breaker that extend longitudinally along the mulling axis with the second thermal breaker attaching the third and fourth plate members;

the second joining plate configured to attach to the first joining plate in an engaged arrangement to join together the first fenestration unit and the second fenestration unit with the mulling axis extending between the first joining plate and the second joining plate;

wherein, in the engaged arrangement, the first joining plate and the second joining plate overlap with the first thermal breaker overlapping second thermal breaker, the first thermal breaker overlaps with the first alignment fin, and the second thermal breaker overlaps with the second alignment fin;

wherein the first thermal breaker aligns with the first alignment fin perpendicular to the mulling axis on one side thereof; and

wherein the second thermal breaker aligns with the second alignment fin perpendicular to the mulling axis on an opposite side thereof.