According to the US copyright office, all buildings before 1990 are not protected by copyright.
Also, windows, doors, and anything that is a necessary structure of a building are not protected by copyrighted.
http://copyright.gov/circs/circ41.pdfIneligible Building Designs
The following building designs cannot be registered:
Designs that were constructed, or whose plans or drawings were published,
before December 1, 1990
Designs that were unconstructed and created in unpublished plans or drawings
on December 1, 1990, and were not constructed on or before December
31, 2002
Structures other than buildings, such as bridges, cloverleafs, dams, walkways,
tents, recreational vehicles, mobile homes, and boats
Some buildings not protected by copyright in the US:
Empire State Building
Chrysler Building
all buildings built before 1990