Retaining historic windows is widely discussed lately, especially in light of energy efficiency and sustainability. We are therefore dedicating a page on our website to share ongoing research and other related information that addresses this issue.
The following website from the State of California shares studies and research on the value of repairing and retrofitting historic windows and misconceptions about new windows. It includes third party studies that demonstrate that repaired windows have equal value to replacement windows in point rating energy systems, with less impact to the environment than new windows. Links provided in this site also address:
Color and the pattern of light reflecting off the glass
Depth and thickness of frames and sills
Improved aesthetics of maintaining original windows