The sustainable-living mantra of “reduce, reuse, recycle” is usually applied to low-tech or consumer goods: things like glass jars, old magazines and obsolete cellphones....

The sustainable-living mantra of “reduce, reuse, recycle” is usually applied to low-tech or consumer goods: things like glass jars, old magazines and obsolete cellphones. But we could become a whole lot more sustainable if we followed those concepts for much larger items as well … say, for example, buildings.

While advanced technologies and green building standards like LEED certification have helped to make many new construction projects ├╝ber-efficient and energy-smart, it turns out that the greenest building of all really is — as architect Carl Elefante has said — “one that is already built.”

A new, first-of-its-kind, detailed analysis shows why, in most cases, renovating an old building in the right way is usually far more environmentally responsible than new construction, even new construction built to the highest, greenest standards.

“(I)t takes 10 to 80 years for a new building that is 30 percent more efficient than an average-performing existing building to overcome, through efficient operations, the negative climate change impacts related to the construction process,” according to “The Greenest Building: Quantifying the Environmental Value of Building Reuse,” a new report from the Preservation Green Lab of the National Trust for Historic Preservation.

For example, if the city of Portland, Oregon, were to renovate and “reuse” all the single-family homes and commercial office buildings that are instead likely to be demolished over the next 10 years, it could cut its carbon dioxide emissions by about 231,000 metric tons. That’s around 15 percent of the entire county’s carbon reduction goals over the next decade.

On a global basis, the potential benefits of building reuse are even more jaw-dropping, simply because of the sheer number of buildings torn down every year. According to the Brookings Institution, nearly one-fourth of all the buildings in existence — covering a total area of some 82 billion square feet — are likely to be demolished and replaced between 2005 and 2030.

The National Trust study compared the potential impacts of remodeling/retrofitting versus demolishing/new construction for six different types of buildings in four different climate zones and found just one instance in which a new building is greener than an old one. Compared to putting up a brand-new multifamily housing project, converting a warehouse to multifamily residential has an environmental footprint that’s between 1 and 6 percent higher.

Of course, there are always caveats. A new building would have to be about the same size, and serve about the same purpose, as an old one to ensure the old-is-better results. Renovations need to use sustainable materials and methods to be green. And, despite the many benefits it offers, building reuse alone won’t help us cut our carbon footprints by the total amount we need.

Finally, there will always be times when renovating an old building just isn’t an option.

“First, the continued use of certain older buildings may be impractical for a number of reasons,” the National Trust study states. “An existing building may not suit a new proposed use that makes sense in the context of its neighborhood, or geographical impracticalities may render reuse unrealistic, e.g. as in the case of many vacant buildings in depopulating cities. Secondly, changing demographics and the evolution of vibrant, successful urban spaces will continue to necessitate new construction. Even so,
a paradigm shift is needed to account for the relative environmental benefits of reuse and to ensure that reuse be seriously considered in decisions regarding demolition and new construction.”