New buildings in Marin will soon be required to go all-electric, part of a suite of new building and electric vehicle charging requirements meant to reduce reliance on natural gas, a major source of greenhouse gas emissions. 

The rules were adopted by the Marin County Board of Supervisors last month. Additional changes slated to go into effect in January include rules that existing homes pursuing alterations or additions of 750 square feet or more implement energy efficiency improvements or increased electrification beyond state minimum requirements. There are also mandates for electric vehicle charging in homes and parking spaces for apartments.

“We are continuing to plan for the future and continuing our transition to a decarbonized building environment,” Sarah Jones, the assistant director of the Community Development Agency, said at an October hearing.

The new rules were prompted by California’s state building codes, which are updated every three years. The state creates minimum standards, along with “reach codes,” or recommendations for jurisdictions that want to go above and beyond those minimum requirements. 

Marin first implemented green building codes in 2001. Originally, the rules included energy efficiency requirements, but they offered no real incentives for appliance change-outs. In 2019, the county introduced its “electric preferred” option for new construction, along with optional financial incentives for remodels or additions to use more energy-efficient appliances. 

Over the past decade, electricity has gotten much cleaner, said Brian Reyes, a county planner in the sustainability division. Data showed that in 2005, 43 percent of Marin emissions from buildings were due to electricity and 57 percent were due to natural gas. By 2020, that had shifted dramatically, with natural gas accounting for 87 percent of building emissions and electricity just 13 percent.

In total, natural gas accounted for 26 percent of all Marin’s emissions, second only to transportation at 56 percent. Overall, electricity accounts for only 5 percent of county emissions.

Addressing greenhouse gas emission is critical “if we are to meet our very aggressive climate goals,” Mr. Reyes said, adding that keeping up with state and market trends meant having code that aligned with an “all-electric future.”

According to a county staff report, over 60 jurisdictions in California, including a number in the Bay Area such as Fairfax, Petaluma and San Francisco, now require all-electric new construction. That goes beyond the state’s minimum requirement that new construction have either electric space heaters or electric water heaters.

Requirements for all-electric new construction in Marin come with certain exceptions, some of which Mr. Reyes said protect low-income populations and seniors aging in place. There are also exceptions for restaurants and for remodels that create accessory dwelling units within the footprint of a home. New detached ADUs will be required to be all-electric.

Homeowners looking to undertake remodels or additions affecting more than 750 square feet—a change from the previous threshold of 1,200 square feet—will be offered a “menu of energy efficiency and electrification measures,” according to a county staff report. Compliance follows a points-based system; homeowners can pick and choose which improvements they want to pursue, as long as they hit a minimum number of points.

Additionally, all new single-family and two-family homes will be required to be ready for electric vehicle charging. Apartments will need to offer E.V. charging for every parking space, a requirement beyond even the state’s reach standards.

The county’s Community Development Agency said one of the greatest concerns it heard during outreach in the past year was the ability of the state’s power grid to handle the increasing push to convert to electric. But county staff said that grid operators like PG&E are planning for increased electric use over time, and the changes won’t come all at once.

Sebastian Conn, a community development manager with Marin Clean Energy, said at the October hearing that “as we embark on a gradual transition to an all-electric building supply, MCE is planning for the increased electricity demand in our long-term power procurement practices.”

Yet Supervisor Dennis Rodoni pointed out that Marin doesn’t have a huge amount of new construction. “We don’t have a lot of new building—we may have more under the Housing Element—so getting these existing buildings to transition is important,” he said.

But homeowners are not required to shift to electric appliances when replacing old appliances. Dana Armanino, the sustainability manager for Marin, said the county isn’t requiring the installation of electric appliances at the time of replacement because they don’t want to “drive a lot of projects underground.” Additions and remodels of a certain square footage, on the other hand, already require permits, so adding the new requirements then makes more sense. 

Mr. Reyes emphasized that although the code changes were important, new rules aren’t the only way to reduce emissions. Pursuing ways to incentivize current buildings to transition was critical to reach the county’s emission goals.

Most public commenters, often associated with climate-focused nonprofit groups in Marin, supported the new measures. But a couple of speakers protested what one termed the “nonprofit industrial complex” and the “consumption of virtue-signaling tech that are pollutants and carcinogens.” 

Another commenter, who said she had biked 20 miles to the November hearing, argued that the reliance on electric vehicles to meet climate goals ignored the harm done by the need to source rare earth minerals for them. The real answers, she said, were reduced consumption and living more modestly.

Mr. Reyes noted that electric vehicles, while important, were not the “sole solution.” Charging stations, he said, were linked not to the number of units in an apartment but to parking spaces so that you’re not requiring that each unit have parking spaces, and he said the agency wanted to get people out of their cars. 

“This is one part of our tool in the toolbox, and we think about many others as well,” he said.