Door assembly

1. A door assembly, said door assembly comprising:

at least one active door panel;

at least one fixed door panel; and

a door frame having a plurality of frame members including a mullion;

wherein the mullion includes:

a core, the core having a core stop end, a core rabbet end, a first core side wall having a first linear plane and a second core side wall having a second linear plane, wherein the first linear plane and the second linear plane are parallel to one another,

a pair of recess points extending into the side walls of the core medially along the first linear plane and the second linear plane, the pair of recess points separated by an intermediate segment; and

a two-piece top piece having a stop portion and a rabbet portion, and

wherein said stop portion includes a pair of extensions that project into a side wall of the core to secure the stop portion onto the core, and said rabbet portion includes a pair of extensions that project into a side wall of the core to secure the rabbet portion to the core,

wherein the stop portion encases the core body on the core stop end and the rabbet portion encases the core body on the core rabbet end.

2. The door assembly of claim 1 , wherein said stop portion extensions project into the core past the linear plane of each core side wall, into one of the recess points along the core side walls.

3. The door assembly of claim 2 , wherein said rabbet portion extensions project into the core past the linear plane of each core side wall, into one of the recess points along the core side walls.

4. The door assembly of claim 1 including a stop surface formed in part by an arm of the stop portion and in part by an arm of the rabbet portion.

5. The door assembly of claim 4 wherein the core fits into a hollow space within the stop portion and the rabbet portion.

6. The door assembly of claim 1 wherein the stop portion includes arms, and the arms each include at least one hollow segment enclosed within each arm.

7. A door mullion comprising:

a core including a core stop end, a core rabbet end, a first core side wall, and a second core side wall,

at least one recess point extending into a first core sidewall and at least one recess point extending into a second core side wall,

a top piece enclosing the core, the top piece including a stop portion and a rabbet portion,

an extension extending inwardly from the top piece, and mating with the at least one recess point along a first core side wall, and an extension extending inwardly from the top piece, and mating with the at least one recess point along a second core side wall, and

a stop surface formed by a U-shaped turn segment of the top piece along each side of the door mullion.

8. The door mullion of claim 7 wherein each side wall includes a linear plane along an outer surface of each side wall.

9. The door mullion of claim 8 wherein said top piece is a two-piece top piece.

10. The door mullion of claim 8 wherein the stop portion and the rabbet portion each include a set of extensions extending inwardly from the top piece.

11. The door mullion of claim 10 wherein said core includes a set of recess points along each core side wall.

12. The door mullion of claim 11 wherein said stop portion includes a pair of extensions that project into a side wall of the core to secure the stop portion onto the core, and said rabbet portion includes a pair of extensions that project into a side wall of the core to secure the rabbet portion to the core.

13. The door mullion of claim 12 including a stop surface formed in part by an arm of the stop portion and in part by an arm of the rabbet portion.

14. The door mullion of claim 13 wherein the stop portion includes at least one hollow segment enclosed within each arm.