Sash windows in period houses have been built based on the golden ratio, a mathematical equation involving two numbers that equals one.618 and provides probably the most aesthetically pleasing structure. This rule was observed inside the width and top of sash windows as well as the proportions with the panes. https://design-your-own-custom-st70119.ziblogs.com/36220286/top-sash-window-draught-proofing-secrets