Old buildings and communities are so important to us because we have to relearn how to design cities like they were before cars, and buildings like they were before there was air conditioning and cheap fuel. Carl Elefante is Director of Sustainable Design at Quinn Evans Architects; He spoke at the Heritage Canada Conference about Old Buildings in an Age of Environmental Crisis. Elefante noted traditional systems of natural ventilation were anything but "passive"- they required the active involvement of the occupants, in opening and closing windows, shades, cranking out awnings and using other simple technologies.
It is the modern systems that are passive as far as the occupant is concerned; set the thermostat and be done with it. But people can interact with buildings and actively participate in a number of ways, from opening windows to putting on a sweater when it is cool. Elefante complains that ASHRAE, the bible that engineers use to design mechanical systems, considers a human being to be "a six foot tall grey cylinder with a single data point," whereas a real human being can loosen their tie when it gets hot.
Carl also makes the point in an essay, "The Greenest Building..." that only about six percent of the buildings in America were built before 1920, the period that preservationists spend their time worrying about; there are 36 Billion square feet of non-residential buildings from the 50s through the 80s that need to be retrofitted and greened. It ain't going to be easy.
Quite frequently, with the preservation of 18th-, 19th-, and early 20th-century buildings, we endeavor to retain or restore their original function as well as fabric. Repairing operable windows, shutters, and awnings on a Victorian house in a historic neighborhood overarched with 100-year-old trees is so obviously a win-win for both preservation and sustainability. The character of a historic resource is preserved and effective weather- and climate-responsive devices are returned to their intended function. But it is hard to discover such win-win scenarios with many, if not most, modern-era buildings. Far too frequently, the windows never operated and the mechanical system never performed efficiently. Something different, something new, something layered on to what already exists is needed.
That is going to be the real challenge; fixing the crap of the last sixty years.