bumping down duplicate post...see link below for other post with replies. Here is a link that might be useful: 1834 windows 6 pane/12 pane

Those of us attracted to this forum have an appreciation for original window sashes and such. The problem is that most in the marketplace do not. We have all seen it, around here beautiful, 19th century houses are routinely razed and replaced by McMansions. A big part of the problem is lead paint and where do we always find lead paint- on the sashes. For those few who actually restore original windows (such as me) where do you get the storm windows? They're gonna have to be custom made right? I searched and searched and finally found The Burch Company in Baltimore, still in business only barely. Another grievance of mine is the slate roofs. I live in an area with beautiful, black slate roofs on all the buildings build before 1920, even sheds and barns. New people who move in don't recognize slate and pull it off and put on the cheap stuff, it happens every day. These actions are governed by the marketplace, so many times the work goes to the low bidder.

I used to have aluminum storm windows and they were such a pain. And they were not energy efficient at all. Mine were 'double hung', meaning they slid up and down. to get a pane out you had to force it to one side, or the other and the other side would clear enough that you could tilt it out for removal. I'm guessing yours is the same way, except you would have to lift the pane up enough so the bottom could pull out a bit and then pull down to slip it out of it's upper channel. The screen works the same way and you may have to get that out first. The best investment I ever made on my home was getting rid of those windows and putting in vinyl clad double pane insulated windows that tilt in for washing.

If you try to remove that pane and leave the existing, uncracked pane in place you will likely have a mess and possibly a loose remaining pane...if it doesn't get broken in the process. I suggest you leave it alone, or, for safety, run wide tape along the crack. If the crack is inside, you can use clear packaging tape; if it's outside, and under an overhang, you could use packaging tape there, too. Otherwise, use duct tape on the outside as it should be able to hold up to the weather until you can manage the window replacement. And you're right...a replacement of that size will be pricey.