You need to find an old window expert. If an internet search doesn't yield results, ask your local historical society or historic preservation board.

The exterior window you are referring to is a storm window. It is a way to keep the historical integrity of the house and provide the protection you need. These would be custom made.

Thanks for your advice.

Does anyone where I can find a window expert in British Columbia, Fraser Valley area?

Will do. Thank you.

Great question renoinfo.

We receive requests for this type of restorative work often. If possible, the best approach is to remove the windows, and have them re-cemented ( http://verrier-processes.blogspot.com/2012/06/cementing-leaded-panels.html). If not feasible, an exterior pane of glass can be a good solution, but it must be installed correctly. Weather/site conditions could allow condensation between the exterior glass and the leaded panel.

Any studio in your general area who does restoration work will be able to determine the best approach for your particular windows and budget.

Good luck with your endeavor!

Thanks so much for the helpful information. Really appreciate it. I had a look at your website; beautiful work.

Thank you for the compliment renoinfo.

Please keep your fellow houzzers posted on your leaded glass project.