Most advances in both exterior door and glazing technology have occurred within the last 25 years. In fact, until the beginning of the 70’s the only significant improvment, in a technical sense, was double-glazing. And while that took place in the mid 1800’s, it didn’t become popular until late 1950’s and early 1960’s. It was the energy crisis, sparked by the oil embargo of the mid 1970’s that replaced complacency with scientific research and development on ways to improve exterior door, patio door and skylight technology. During the last decade in particular, we have made remarkable progress toward making exterior doors more energy efficient.