Last week at the climate talks in Paris, world leaders committed a full day to discussing public policies and financial solutions to reduce carbon emissions within the building sector. It’s widely documented that buildings are the culprit for at least 30% of global greenhouse gas emissions . Meanwhile in the building sector, there’s an ongoing discussion about what to do with inefficient buildings from past eras. Debate around historic value versus economics inevitably leads to the big question: Are these buildings worth retrofitting, or do we tear them down and start over?

Lever House, completed in 1951, was retrofitted in the early 2000s. Flickr user Seth Tisue

During the golden era of building post-WWII, an estimated 30 million commercial structures were built, many of them high-rises, containing workplaces and housing in all the major cities. The most notable of them–designed by significant architects such as I.M. Pei, Mies van der Rohe, Eero Saarinen, Edward Larabee Barnes, and Philip Johnson, and firms such as Harrison & Abramovitz, SOM, and HOK–were innovative for their time and are engrained in our collective urban mind. What are the ethics of intervening in these mid-century structures to bring them up to energy code compliance?

Left Behind By Advancing Technology

I live in Society Hill Towers, an I.M. Pei-designed high-rise complex in Philadelphia. At the age of 12, I saw the three towers emerge from the ground during a stopover on my way to the 1964 New York World’s Fair. Fifty years later, the residents are debating how to make the buildings energy efficient without destroying their character, which mainly comes from the distinctive egg-crate exo-structure of concrete and the floor-to-ceiling windows. The windows are the most critical aesthetic feature of the building. Further, the light, views, and how we inhabit the space all depends on these magnificent windows. Unfortunately, they are leaky and provide poor insulation. To change them will require massive renovation within each apartment in the building. What to do? The condo board has employed best practices to reduce overall energy costs, from upgrading the boiler, to replacing pipes, to installing LED lighting. Yet, the windows remain the single most wasteful element. So, the debate continues.

Along with the benefit of expansive views and light came the problem of managing solar heat and energy loss.

Mid-century design and construction advanced the creation of building envelopes. Thin-walled glass construction evolved as an alternative to load-bearing masonry walls with punched windows. Along with the benefit of expansive views and light came the problem of managing solar heat and energy loss through those big panes. But soon enough, as pointed out almost twenty years ago by Alan Cunningham in his book Modern Movement Heritage, how to deal with the design intent of these mid-century curtain walls alongside rapidly advancing facade technology became a conundrum. If we can’t upgrade a building without altering its character, are these structures worth saving in the first place?

The glass of the 1952 U.N.’s Secretariat building was recently replaced. Flickr user John Gillespie

Worth Saving? 3 Key Questions

A 2013 report written by the sustainability consultants Terrapin Bright Green with strategist Bill Browning, “Midcentury (Un) Modern: An Environmental Analysis of the 1953-1978 Manhattan Office Building,” recommended that it was better for the environment to tear down these sorts of buildings, maintaining that even a retrofit with double- or triple-glazing would not go far enough to make a building energy efficient by today’s standards. While this is a provocative proposal, in order for us to come to terms with a viable answer, we must ask a set of deeper questions. Here are three to start: