What a great idea to duplicate old windows. My daughter has a 150 year old farm house with original windows. They are held open with pins in a limited number of locations. This design was prior to the great invention of counterbalanced windows with a rope and pulley system. This system was really great when a rope broke and you had to tear the whole window apart to replace the rope--if you were lucky enough to get it apart with all the paint. Then you can enjoy finding pulleys and sash weights for your new window as well as the extra routing for the knots. Don't forget the benefit of the heat loss through the sash weight cavity.
While the stops were being painted in, the windows were abrading themselves so that the windows rattle very nicely and let in great drafts. It's hard to measure, but the single strength glass does add to the outdoorsy feel on a winter day.
Keeping them clean is real easy. You either sit on the sill with the rest of your body outside and try to clean while the cleaner is dripping on your lap or work from an outside ladder. And they have a lot of small panes of glass because big panes were expensive back then but this is architecturally chic today. Have fun making the muttin bars to duplicate this.
My daughter will have a whole bunch of old windows that you can have for duplicating. These will be available as soon as the budget allows for total replacement. If you enjoy neat features like through mortices, they are great. But along with this comes features like the heat loss and being easy to paint shut.