Environmentally friendly construction has reached a new milestone in Seattle. Last year, the majority of new homes in the city were certified by Built Green, a set of standards for energy, water, and building material efficiency.

In 2016, 52 percent of homes built in Seattle have obtained Built Green certification. The program has certified more than 31,000 units in Washington.

Editor’s note: This post has been updated to clarify that the majority of new homes built in Seattle have Built Green certification, rather than the broader region.

That uptick is driven by government incentives that encourage builders to obtain the certification, according to Leah Missik, regional program manager for Built Green. In Seattle, builders who receive a four-star Built Green rating or higher can obtain their permits more quickly.

Seattle’s population boom, driven by record job growth in tech and other industries, has builders scrambling to add housing inventory to keep up with demand. “Having that permit quicker is huge for a lot of builders,” Missik told GeekWire.

Seattle City Light also offers builders a $1,500 rebate for units that exclusively use electric heating. Missik says incentives are a “huge factor” contributing to Seattle’s new sustainable construction milestone.

“We can actually chart out, over time, our certification … and compare that to how incentives are being taken advantage of in the City of Seattle and we can see that they’re directly correlated,” she said. “So we know that the incentives are a big factor in pushing builders to build green and that’s why we have the 52 percent market infiltration last year for new residential construction.”

Built Green certifies homes in four tiers, depending on how many items they check off on a list of factors that contribute to energy efficiency and environmental preservation. For example, builders can earn points for landscaping that prevents water runoff into Puget Sound and avoiding toxic materials like carpet. One item on the list includes smart home monitoring, which Missik says is on the rise.

“I would say that most of the homes that we would classify as net-zero energy ready or better — basically that means the home is as efficient as possible so all you have to do is add some solar panels and it would produce enough energy to cover the entire home — most of those homes have some smart home technology,” Missik said.

Built Green was created by the Master Builders Association of King and Snohomish Counties in 1999. In September, the association released a study to show the energy savings associated with Built Green certification.

Researchers compared the energy use of Built Green homes and non-certified homes using Seattle City Light data from 2014. They found that homes with Built Green certification used about 40 percent less electricity, amounting to approximately $500 in annual electricity bill savings.

“The Built Green program has really had a huge impact on the Puget Sound region and a lot of that is thanks to cooperating with municipal governments and other entities so we can figure out a win-win solution, so we see more green building, so builders are willing to do it voluntarily, and so we see a better environment overall,” Missik said. “I think this is a really good example of how you can spur more sustainability in a really effective manner.”

KUOW first reported on Seattle’s Built Green milestone. Read and listen to their story here.