Glass is set to the front of the system to maximize thermal performance and is glazed from the interior of the building for labor savings. The YWW 40 T system is thermally broken by YKK AP’s patented MegaTherm® technology. The assembly sits down on a thermally broken sill flashing member. Head, horizontal, and sill members are secured to the two piece vertical members employing YKK AP’s patented screw spline assembly.

Product Data


Thermally Broken


  • Screw Spline Construction
  • Separate Interior/Exterior Finish Options


Construction Use: New / Retrofit

Sightline: 2″

Mullion Depth: 4″

Framing Installation Method: Vertical Through / Screw Spline

Glazing Installation: Inside

Glass Type: Insulating

Glass Configuration: Front

Thermal Method: Iso Struts