Ours is a 1912 Sears kit (at least partially). We have been working on it for two years and the wiring, plumbing, and heating system (95% efficiency condensing gas boiler and wall mounted radiators) are all the latest good stuff. I finally did all the prep work in the attic and will upgrade next week from what is probably an R-8 average to an R-50 using our sprayed cellulose insulation. The walls I can't do much about, they are brick and "pen tile", a hollow clay tile that used to be manufactured at a state penitentiary. Lots of mass but minimal R value. The radiant heat allows us to be comfortable at lower air temperatures, though, so the heat loss is reduced from what it might be with a forced air system.

Still a lot to do and I expect my Christmas presents to mostly be things like light fixtures and storm windows! Something to play with on Christmas day, oh boy!! ThumbsUp

You never change things by fighting the existing reality.
To change something, build a new model that makes the old model obsolete.
R. Buckminster Fuller