The difference is in the overall jamb depth and required components:

For new construction, the flash flange on the head of the unit is left intact; for retrofit, it is removed.

Also, on a new construction unit, three more flash flange pieces are supplied (in addition to the one shown in the photo). They are installed on the sides and bottom of the unit during installation.

A retrofit unit requires no additional components and should be sized as noted in the photograph below and in Figures 2 and 3.

New Construction: The flange is installed against the exterior face of the wall (either sheathing or insulation board). As you can see in the photo, there is approximately 1.375″ to the left of the flange for J-channel or exterior wall treatment. Note: On new construction brick or masonry installations, measure the entire wall thickness.

Retrofit: With retrofit, the full wall width should be considered: exterior face to interior face.

Fig. 1

Measure for retrofit vs. new construction

Measuring New Construction (Fig. 2)

Measure the jamb depth from #1 Interior Wall Face to #2 Exterior Sheathing. (Measurement does not include siding or exterior finished surface.)

Retrofit jamb thickness

Measuring Retrofit (Fig. 3)

Measure the jamb depth from #1 Interior Wall Face to #2 Exterior Wall Face

New construction jamb thickness

Posted in: Series 2050 Garden Window