Reuters
But what if the new building is super energy-efficient? How do the two alternatives compare over a lifetime, across generations of use?
“We often come up against this argument that, ‘Oh well, the existing building could never compete with the new building in terms of energy efficiency,’” says Patrice Frey, the director of sustainability for the National Trust for Historic Preservation. “We wanted to model that.”
Preservation Green Lab, the Trust’s sustainability think tank, has published a new study today examining this that puts big numbers behind the finding that the greenest buildings aren’t in fact state-of-the-art ones; they’re the ones we already have.
Retrofit an existing building to make it 30 percent more efficient, the study found, and it will essentially always remain a better bet for the environment than a new building built tomorrow with the same efficiencies. Take that new, more efficient building, though, and compare its life cycle to an average existing structure with no retrofitting, and it could still take up to 80 years for the new one to make up for the environmental impact of its initial construction.
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