Viridian Window Restoration brings the
Bi-Glass System to the West Coast!

With over 25 years of successful historic restoration work on the East Coast, the patented Bi-Glass System® is now available in the Pacific Northwest! The Bi-Glass System® will replace single pane glass with high-quality insulated glass units while still retaining your old sash, including divided lights! Reusing your old sash saves money and maintains the architectural integrity of your house or commercial property. After adding new weather-stripping and hardware (or keeping your old hardware if it's in good shape), you will have a truly energy-efficient window unit that will keep you warm in the winter and cool in the summer.

There are a number of options for balancing your sashes once the glass has been replaced with new energy efficient insulated glass units:

  • You can keep the original sash weights and pulleys! We will replace any broken components and install new sash cords and some added weight to compensate for the heavier double pane glass. This is our favorite option as we are historic preservationists at heart!
  • Another option is installing new channel balances (sometimes called "invisable balances"). With this option the sash cords are removed along with the sash weights and the empty pocket can be insulated.

Before and after cross sections of single to double pane window glass replacement:



Product Information:

Viridian Window Restoration/Bi-Glass System® Components:


  • Insulated glass comes in 7/16" to 1" thickness. Our normal size for most jobs is 1/2".
  • Restoration glass (wavy glass) is available to maintain the old look. However, it is VERY expensive, so most of our clients choose standard IGU's (insulated glass units).
  • Low-E coating and Argon gas are standard in our units, but other configurations are available for special situations.
  • Single pane restoration and/or replacement is available when appropriate.
  • Replacement of old fogged glass (failed IGU's) with new units is available for modern windows.

Balance System:

  • Our standard option is to refurbish weights & pulleys.
  • New hidden balances are an option when appropriate.

Weather Stripping:

  • New silicone bulb weather-stripping at all horizontal surfaces.
  • Brush strips and extruded polypropylene weather-stripping systems for vertical surfaces ensures elimination of rattle and smooth operation.
  • Note: All of these weather stripping elements are virtually invisible!