Triple pane glass and ESP (energy saver package) You can't go wrong with selecting the 500 Series Insul-Tec sliding window with ESP. The 500 series is one of the top picks for beauty, durability and performance. When you are ready to replace those drafty windows choose Okna and Wonder Windows Buffalo. 
  • 30% Better than Energy Star® minimum
  • 333% Better Air Infiltration protection than Industry Standards.
  • Triple pane glass
  • 3¾" Depth Welded Mainframe with superior strength long lasting performance.
  • The Heatseal® warm edge spacer system provides excellent thermal efficiency 
  • Full integral interlock with double weather-stripping.
  • Optional Auto-Locking system
  • Heavy gage fully extruded handles 
  • Factory installed Fiberglass mesh half screens come standard on all windows
  • Great for Replacement and New Construction applications
  • Available in 2-lite and 3-lite choices
  • Available grids between glass in Common Grid Patterns
          Energy Star Comparison To
Glazing Option U-Value SHGC VT CR Minimum* Energy Star Minimum
Triple Glazed              
With ESP 0.21 0.26 0.42 70 0.30 30% Better


      Industry Comparison To  
  OKNA Windows Minimum Industry Minimum  
AAMA Rating  R40 R15      
Air Infiltration cfm/ft2 0.09  0.3 333% Better
Water Penetration mph    59  33   79% Better  
Structural Integrity mph  153  94   63% Better