I’m considering buying a 2 1/2 story older Foursquare home built in 1926 located in northern Virginia. The house was built by a building contractor as his personal home. The house is in excellent condition. During the home tour I noticed the inside of the perimeter walls had no Sheetrock or insulation and only covered in wallpaper. When I got up to the attic I could see concrete block had been covered with a thick coat of cement and then plaster. The roof is standing seam metal. No insulation in the rafters. The house has only exchanged owners a few times and most everything is original. Having no experience with rock faced concrete block homes I don’t know if insulation is necessary? I’m concerned I will be able to keep it heated or cooled.
In 1926 they didn’t worry about insulation, oil was cheap. The blocks have “open cells” in them that could be filled with insulation, but I doubt it. Usually reinforcing is installed in most of those cells.
However, insulating the walls should be done after you 1) caulk all the cracks around windows and doors to cut down on drafts, 2) insulate the attic, heat rises so it’s VERY cost effective to add insulation in the attic, 3) up grade furnace, thermostat and air filter, if any, and upgrade hot water heater.
Replacing single pane windows with thermal pane windows and insulating walls is usually not cost effective.
I agree with @ecnerwal, get a copy of the heating bills.
The only thing that is worse than straight masonry for insulation value is metal. It takes about 4.5 feet of masonry product get the same insulation value as 3.5 inches of spun fiberglass.