Mrs. Tunachucker and I bought a house that was built in 2 sections- the NEW part of the house was constructed in the early 1900's...the original section of the house was built pre-civil war. The windows are old, wooden, and have many cracked or missing panes. There's storm windows on them that were installed at some point in the past, but at this point nothing seals very well and it all looks very tired. We've tossed around the idea someone suggested above- restoring the windows in one room (our bedroom seems like a good starting point, since we'd like that room at least to be cozy in the Maryland winters) and then deciding if we want to continue that process or start looking for modern replacements.
I have heard that, ballpark, a well-restored original wood single pane window with storm window is about 80% as efficient as a high-quality modern double hung fancy window. They key word being "High-Quality". There is some modern, double-hung stuff out there that is junk, and weatherstripping does degrade over time. Naturally, cheaper stuff degrades faster.
A bigger issue I recently discovered: the house is heated with a hot water boiler/ radiator system, and most of the radiators are cracked/ leak. The boiler seems to be fairly new, at least, and the pipes seem solid. So we're tossing around replacing the radiators, vs installing electric baseboard heaters, or possibly a heat pump. The problem, of course, is ductwork- running ductwork in a 100+ year old house isn't straightforward.
In the meantime, we have no heat in the house. We do own 4 electric space heaters, and a couple of those propane jobs...
Tunachuckers: 15 Years of Effluency
'08 - '10: 1966 Volvo 122, "Charlie"
'10 - '18: 1975 Ford LTD Landau --> 2018 - current: Converted into 1950 "Plymford"
'22 - current: 1967 Volvo 122, "Charlie ]["