Hurd glazed its wood windows with a new technology to achieve insulation values it says are equal to, or greater than, a fiberglass-filled exterior wall. The Ultra-R glass option with Heat Mirror technology suspends layers of film, coated in nanoscale reflective particles, in krypton gas between the panes. The system blocks heat transfer, ultraviolet rays, and even sound, resulting in windows that reach values up to R-20 and are 33% lighter than standard triple-pane units. 800.433.4873.