We have a late 1800s brick house in the Midwest ( Zone 5A ) with original double hung weighted sash windows. The current configuration includes poor quality combination storm windows. I would like to improve the performance of the windows and am looking for advice about storm windows that would be appropriate for the appearance of the house. We live in a designated “historic district” so appearance from the street is important. I’ve considered interior “storm windows”. What advice can you offer?