Heat Mirror™ advanced insulating glass systems are found in the most energy efficient windows on the market today. With the UV protection, energy efficiency, and quality, the Heat Mirror technology is second to none. Insulating glass made with Heat Mirror technology can have an R-value from 6 to 20, which can insulate as well as typical walls. With installing windows with Heat Mirror technology, you are not only taking steps to lower your energy bill but you are also taking steps to protect your loved ones from UV rays.