Links 

Ten top reasons to repair and restore wood windows

A few links to energy savings and comparison information along with discussions on sustainability

http://www.dahp.wa.gov/sites/default/files/Windows%20Energy%20Efficiency%20Facts%20and%20Myths.pdf

http://forum.savingplaces.org/connect/community-home/librarydocuments/viewdocument?DocumentKey=59eab0e4-f0f4-45c5-97c8-147a8def82ae&CommunityKey=00000000-0000-0000-0000-000000000000&tab=librarydocuments

Here is some information from the U.S. secretary of the interior on rehabilitating and preserving historic windows.

 https://www.nps.gov/tps/standards/rehabilitation/rehab/windows01.htm

https://www.nps.gov/tps/how-to-preserve/briefs/9-wooden-windows.htm