Hopesprings, You cannot just replace one pane of glass, the entire IGU needs to be replaced. My comment as to whether I would not be sure about replacing an IGU in an 18 year old Hurd has to do with what I usually see as the observed condition of 18 year old Hurds. If the windows are otherwise in good shape, replace the IGU. You are certainly in the minority though with having 18 year old clad wood windows being in good shape. Props to you for obviously maintaining them if that is the case.

We have casement windows one fixed and the rest operable. A couple years ago when we decided it was time to address leaky seals and wood rot. Some of the windows only needed just the glass replaced (on site). Some needed new sashes (glass with its wood trim) and some needed to be completely replaced. I think you should see what another window place/ contractor has to say

"replacing the actual window makes much more sense. I think just repairing the seal is a cheap band aid." You young whippersnappers, you always want to throw stuff away when it can still be fixed. Get off my lawn, willya? No! Not that way! Don't run through the flower bed! :-) Seriously, I can't imagine replacing an entire window just because one part needs to be changed. Unless the window is falling apart (and this one doesn't appear to be), that's way more expense and labor than necessary, not to mention the waste of raw materials and landfill space.

The windows are Pozzi and still in good condition (other than the seals!). I am guessing that the door is Peachtree because that is what the other doors in the house were. Because the door sizes have changed, the price to replace all the glass is way under what a new custom sized door would be. We have replaced all the other doors in the house and had to have custom doors made. We replaced 2 of them because of issues with replacing locks and handles. The other doors were replaced because they were sliders/french doors that were just not holding up well. This door is seldom used in a walk out basement and still works fine.