In the city, buildings emit the bulk of air pollution. As the de Blasio administration seeks to slash greenhouse gas emissions, it's helping teach building owners how they can help save not just the Earth—but money, too. One way to do that is simpler than you may think. NY1's Josh Robin filed this report.

You may not be feeling it these days, but it's there—the sun.

The de Blasio administration wants you to see more of it in your home and office.

"There's a huge opportunity to save tons of energy—and tons of money," says Richard Yancey of Building Energy Exchange.

It's called building energy exchange.

A non-profit in a city building, Building Energy Exchange is funded with taxpayer money.

There, the city hopes models will convince landlords to reconfigure spaces—letting the sun shine in, flicking light switches off.

Yancey, the organization's executive director, says a retrofit won't cost much.

"The return on the investment can be very short," Yancey says.

When there's no daylight, there are new LED displays, lights using solar power and even gravity.

A planned expansion will allow owners to brainstorm with contractors and financers about greening buildings with more than cleaner lighting.

"We're a city of islands. And so climate change will affect us in ways that it won't necessary affect other cities, and we just have to do our part," says Nilda Mesa of the Mayor's Office of Sustainability.

"Maybe even the best consultants don't know what the best technologies are, so we really need to have a conversation with everybody involved on all levels of a building - to move the City forward," says Angela Pinsky of the Real Estate Board of New York.

The city aims to reduce greenhouse gas emissions 80 percent by 2050, and it now uses a combination of carrots and sticks to get building owners to make their properties more energy efficient. Officials leave open the possibility, though, of more sticks—like fees.

"Having some mandates is on the table, but we think that there's a pretty strong case to be made that we can really achieve a lot without getting to that point."

A case that it's ultimately more economical, even with low oil prices now.

Yancey says there is more to consider than money.

"There is no Planet B. I think this is the challenge of our generation."