In recent days, I asked the question, “what one change would you make to LEED to encourage green building?” to four score and seven people familiar with green building.

This was a highly unscientific poll that is not representative. The small sample was not randomly selected, but rather each was a professional working on green building projects, so the results have some statistical reliability. And when coupled with the result that more than 50% offered the same solution and the next offered solution polled at only 8%, the responses to this question, posed by someone not associated with the U.S. Green Building Council, are a useful tool of analysis.

Against a backdrop of the increasing belief, as recently articulated by Bill Gates that current green technologies can reduce carbon dioxide emissions and the human contribution to climate change only at costs that are “beyond astronomical” many have begun to focus on another frontier of innovation, on using energy more efficiently, and thus using less of it. Given that green buildings regularly consume 25% less energy or more, green building may be the single greatest current opportunity to address climate change.

There are nearly 4. 9 million commercial buildings in the U.S. which makes existing buildings the target rich environment (i.e., each year only about 170,000 new commercial buildings are constructed). And those existing buildings are tremendous consumers of electricity, accounting for 74% of the total electricity consumption in the U.S.

There are a variety of green building standards, codes and rating systems, but LEED commands a more than 95% market share in the U.S., so the answer may be expressed in terms of LEED.

And the LEED for Existing Buildings: Operations & Maintenance rating systems are highly regarded when they identify and reward current best practices and provides an outline for buildings to use less energy and uncover operating inefficiencies.

In 2014, LEED for Existing Building Operations and Maintenance was once again the most popular rating system, with existing buildings representing 48% of the total square footage LEED certified.

But the problem is that since LEED EB was launched in 2004, today there are only a total of 3,778 certified LEED EB buildings. That is less than one tenth of one percent of the 4.9 million existing commercial buildings.

However, an existing building that cannot achieve an Energy Star Portfolio Manager rating of 75 is excluded from participating in LEED v4. (An Energy Star score of 75 means the building is performing better than 75% of similar buildings nationwide.) The prerequisite of a minimum score of 75 arguably excludes 75% of all existing buildings from participating in LEED. This is more significantly stringent than LEED 2009 requiring an Energy Star score of 69.

There is a pilot credit known as “EAp2 Energy Jumpstart” such that an existing building that reduces energy consumption by 20% is now LEED v4 eligible. But, after much internal debate, it is only a LEED pilot credit and available to only the first 500 applicants.

Which gets us back to the question, “what one change would you make to LEED to encourage green building?” The number one answer, by far, allow every existing building that improves its Energy Star score by at least 20% to be LEED EB eligible!

That single change to the rating system would make millions of buildings eligible to participate in LEED and may be the single greatest current opportunity to address climate change.