Sacramento’s Golden 1 Center has been celebrated as one of the greenest buildings on earth.

Before the new arena even opened, Green Sports Alliance executive director Justin Zeulner said, “The consensus is when this opens, Golden 1 Center will be the most ecologically innovative and environmentally friendly building, not just in sports, but … on the planet.”

Indeed, the U.S. Green Building Council gave Golden 1 Center LEED Platinum certification, which Sacramento Kings president Chris Granger says puts it in the top three percent of all buildings in the world.

This all goes to show: The environmental impact of a green building can be… not-so-green.

Back when the city was in the planning stages for the new arena, Sacramento resident Rick Bettis asked the city about the greenhouse gas emissions related to the construction of the arena.

“I think it’s important, because when you make that analysis, the initial greenhouse gases related to the construction of a project are substantial, and you have to kind of make up for that over the period of the lifetime of the project,” Bettis explained.

There are people dedicated to conducting this type of analysis. They’re called carbon accountants, and they’re often hired when people want to offset greenhouse gas emissions by protecting forests.

Consultants for the city estimated that the demolition and construction of the new arena would add more than 219,000 metric tons of CO2e, or carbon dioxide equivalent, to the environment. Carbon dioxide equivalent is a unit of measure of greenhouse gas emissions.

ABC10 asked Carbon Accounting Company president Ian Lipton to weigh in on this estimate.

“You’re saying 219,000 metric tons for the construction phase?” Lipton asked. “Oh yeah, that’s huge.”

Back to Bettis’ initial question: How long will it take to offset this impact, through the improved efficiency of Golden 1 Center compared to its predecessor, Sleep Train Arena?

Lipton explains how one would calculate this. A carbon accountant would take the annual greenhouse gas emissions of Sleep Train Arena, and subtract from that figure the smaller emissions from Golden 1 Center. That total would be divided into the 219,000 metric tons from the construction of Golden 1 Center.

The answer? The number of years it would take to offset the carbon footprint.

This is where it gets interesting.

“[We] never calculated the thing that was being left behind,” city consultant Brian Boxer told ABC10.

“Maybe it’s my perspective. I think maybe it’s an interesting question, but I’m not sure it’s a particularly useful question,” Boxer added.

Lipton vehemently disagreed.

“I think it’s a completely valid question, because it’s a significant contributor to emissions. If we dismissed certain activities outright, then we’re not being responsible for the decisions we make,” Lipton said.

For a sense of how significant the contribution is, 219,000 metric tons is equivalent to driving nearly 525 million miles, or as Lipton put it, adding 40,000 cars to the road.

Boxer – the consultant for the city – said using greenhouse gas emissions as a metric would stifle new development.

“The net impact of building anything will be more than doing nothing. We could not grow. We could not build anything,” he said.