large as 8½ by 10 feet - and so all the glazing in the house is 1/4" plate glass, with an R-value of 1. Replacing it all with insulated glass to save energy would have a payback period several times the warranty for the new glazing - which has a perimeter seal between its two or more panes, subject to eventual failure. The original glass, which has no such failure mode, remains clear after 50 years. Further reading "A Powerful Design in Fieldstone", Architectural Record Houses of 1961, pp. 70–73 Marcel Breuer Digital Archives, http://breuer.syr.edu/project.php?id=566 References Houses completed in 1960 Houses in Baltimore County, Maryland Modernist architecture in Maryland Marcel Breuer buildings