In JFK's first year in office, architectural historians knew, roughly, -0
about cities and buildings.  Since then we've learned a little.  A very
little.

As I recall, the preferred preservation techniques in 1960's involved
aluminum siding, plate glass windows in historic buildings, and floods of
roofing tar.  What do you "heavy conservationists" think has been learned in
the last 40 years - and what are the biggest unknowns (Ralph: please exclude
improvement of ivy poison techniques.)

Christopher Gray