Because of their additional thickness, the Magnum series windows need jamb liners when installed in residential depth jambs. But it's not a conventional Jamb liner. It is very minimal and inconspicuous and it's paintable so that it virtually disappears into the window frame. Because of the design of our jamb liner, we can utilize a much more appropriate weather-stripping system on the vertical sash edges.
In the world of wooden windows, the universal solution to air-infiltration around the vertical edges of the sash are "Jamb Liners". The jamb liners mount on either jamb side and the rigid vinyl "springs" against the edges of the sash to make a seal. As long as the sash edges are smooth and the jamb liners continue to "spring" to make contact, the system works pretty well. If one doesn't mind seeing a great deal of either white or beige vinyl around the perimeter of the sash it's a fairly acceptable solution.
There is essentially no weather-stripping on the edges of most contemporary wooden windows. The Jamb Liners act as weather-stripping by springing to and mating with the wooden surface of the edges of the sash. This approach works well when the windows are new, and all surfaces smooth.Some find this "protruding" Jamb Liner concept less than desirable because a great deal of vinyl is visible and the vinyl is usually only available in white and beige.