When the United States Green Building Council (USGDC) began its work in the 1990s, one challenge quickly became apparent: defining what exactly makes a building “green.”

Without a clear standard, sustainability remained subjective. One project might emphasize energy savings, while another focused on materials or water use. There was no consistent way to measure or compare performance.

To address this challenge, the USGBC developed the rating system known as Leadership in Energy and Environmental Design (LEED).

Introduced in 2000, LEED was designed to provide a comprehensive framework for evaluating the environmental performance of buildings. It was not a building code, and it was not mandatory. LEED offered a voluntary system that design professionals, developers and construction companies could choose to follow in order to demonstrate higher levels of sustainability.

An important feature of LEED is its emphasis on documentation and verification. To earn certification, project teams must provide evidence that they have met the required criteria. This process is reviewed by a third party, helping to ensure consistency and credibility.

So, the doubtful might ask, “Why would a building owner or developer choose LEED over business as usual?” The answer is found in the potential benefits of LEED:

First, it can reduce operating costs. Energy-efficient systems and water-saving strategies often lead to lower utility bills over time.

Second, it can improve occupant experience and health. Better air quality, natural lighting and thermal comfort can enhance productivity and well-being.

Third, it can provide a market advantage. LEED-certified buildings are often seen as more desirable by tenants, investors and the public and can generate a higher return on investment.

However, LEED is not without its critics. Some have argued that the system can be complex and costly to implement. Others question whether point accumulation always reflects meaningful performance improvements. For example, a building might earn points in one category while underperforming in another. The USGBC has not shied away from these concerns, which is why the standard has evolved over its lifetime and has had a significant impact on the industry.

LEED has introduced a common language for sustainability and encouraged designers to think more holistically about building performance, and it has shifted expectations. What was once considered “green” is increasingly becoming standard practice. LEED serves as a tool—a structured way to move the industry toward better outcomes.

In doing so, the USGBC has helped redefine what it means to design and build responsibly in the modern era.