This article from Building Science contributor, Betsy Pettit, features an excellent example of a century home undergoing an energy efficiency retrofit. The Four Square style of building is especially good at staying comfortable over its lifetime, given the simple cube shape that maximizes volume compared to the heat-loss surface area.

The American Foursquare, a Sears, Roebuck & Co. kit home, was a staple of small American towns between 1908 and 1940. More than 100,000 of them were built in America. Sears offered 15 styles of Foursquare kits, which were available through the mail-order Modern Homes program. These homes arrived via boxcar, making them particularly common in neighborhoods near rail lines.

BSD-139: Deep Energy Retrofit of a Sears Roebuck House-A Home for the Next 100 Years