Truly sympathetic georgian style sash windows should also mirror the size and spacing rules as defined by the golden ratio i e.
Golden ratio roof pitch.
A ratio of 1 1 62 is known as the golden ratio and therefore the vast majority of roof pitch in degrees charts you see will be working to this ratio at the very least.
The symmetrical front elevation of a truly quintessential georgian property for example could encompass the golden ratio into its proportions with its height width door and window positions and sizes all relative to the size of its roof pitch.
The golden ratio without going into the minutiae that are drilled into all students at architectural school the golden ratio a ratio of about 1 1 62 simply acts as a benchmark against which any architect that finds a design unsatisfactory can test his intuition.
Designers are often asked to reduce the pitch of a roof by planners because it is considered to have too great an impact on the adjacent buildings.
If a window is one unit wide it should be 1 618 units tall spanning six over six panes combined with slim.