“We’re so pleased that the Impact Estimator for Buildings helped make a quantifiable case for the retrofit of these iconic buildings over demolition.”

- Jennifer O’Connor 
Athena Institute 

As embodied carbon increasingly enters the sustainability conversation, questions about when to tear down and when to retrofit have become more complex. 

The Athena Impact Estimator for Buildings can answer those questions with surprising accuracy and it was used in a study to compare two options: rebuild the iconic but aging UN Headquarters campus or engage in an extensive retrofit.

In order to make the most cost effective and sustainable choice, the United Nations (U.N.) commissioned a report by Vidaris Inc. and Syska Hennessy Group. They used the Impact Estimator in a life cycle assessment (LCA) to determine if the retention of major mass materials would generate large enough embodied carbon emission savings to justify a retrofit over new replacement buildings.

The LCA and operational energy modeling indicated that retaining the building’s structural components, opaque envelope and core walls prevented the emission of 50,000 metric tons of CO₂ while upgrades in glazing and mechanical systems additionally cut GHG emissions from building operation by 65%.

Key Findings:

• Building preservation and retrofit is a key sustainability strategy.
• LCA study using our Impact Estimator showed that rehab instead of new construction prevented the emission of 50,000 metric tons of CO₂.
• A replacement building with better energy performance would take at least 35 years to pay back its embodied GHG debt (and perhaps up to 70 years, which would exceed the building lifetime).

To view the full study, click here:

Assessing the Carbon‐Saving Value of Retrofitting versus Demolition and New Construction at the United Nations Headquarters. Vidaris Inc. and Syska Hennessy Group. December 2016