Usually a preserve for fine town houses, shutters can be installed over your sash windows adding a beautiful and useful detail. As English Heritage state in their video (link), draught proofing your windows and incorporating traditionally made shutters offer about the same insulation as does double glazing but for less than half the cost and thrice the beauty with added security to your property. They can be finished waxed or painted. When not in use they'll simply fold into traditionally made side cases. Where this isn't possible we can construct a traditional housing for them underneath the window.
More info and picture detail is on the way!
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