New development near Union Station. With the District’s housing market back on track, some city lawmakers are urging Mayor Muriel E. Bowser to consider implementing “inclusionary zoning.” (Jahi Chikwendiu/The WASHINGTON POST)

If you don’t work in housing development, you may have never heard of inclusionary zoning. But District officials said it is an important item in Washington’s affordable housing “toolbox,” and it could be key to keeping neighborhoods diverse as local rents skyrocket.

Inclusionary zoning means that new rental or condominium buildings with more than 10 units, as well as any renovations that more than double the building size, are required to make 8 to 10 percent of units affordable to working and middle-class families.

The city pays for it by allowing developers to build extra units to compensate for the cheaper ones. The program has been in effect since 2008, but it has not had a great reputation.

The city began implementing it when the housing bubble burst, effectively halting new development for a while. Critics also complained that the program’s lottery system sometimes failed to match eligible tenants and buyers with affordable units and that condo units sometimes were not affordable enough because of extra costs, such as condo fees.

Now that the District’s housing market is back on track and developments are popping up across the city, city lawmakers are urging Mayor Muriel E. Bowser and the District’s housing authorities to give the program another look.

On Tuesday, the D.C. Council passed a resolution that emphasizes the program’s potential and suggests ways to make it better — such as increasing the overall number of inclusionary units and setting maximum rent, purchase price and eligibility thresholds to make sure that the units are affordable.

A resolution is not legislation — and pertains to one of a number of different affordable housing programs that the city has at its disposal, conceded council member Elissa Silverman (I-At Large), who introduced the measure.

But Silverman said the resolution “lights a fire” under the mayor’s office, and “gives a strong message to the administration that the council thinks this is a tool that needs to be used.”

Bowser (D) has made affordable housing one of her top priorities, appropriating almost $178 million for programs in the coming 2016 budget and an additional $146 million to house and feed the homeless.

The measures are designed to help meet the needs of a city with a widening income gap, rising rents and a growing homeless crisis.

Inclusionary zoning’s backers — including Silverman and nine other council members — said inclusionary zoning should be an important component of that strategy and represents an almost tax-free means to hold on to the District’s middle-class residents when the region’s area median income is so high that even families with traditional middle-class jobs — as nurses, teachers and government workers, for example — have trouble paying the rent in many parts of the city.

“Inclusionary zoning is focused on helping our working residents be able to live in parts of the city that they otherwise wouldn’t be able to live in,” Silverman said.

Ideally, it would also prevent the District’s rapidly gentrifying neighborhoods from winding up like Georgetown and some other parts of Northwest — rich, white and utterly out of reach for much of the middle class.

“It’s a tool for sort of that midrange of affordability,” said Polly Donaldson, director of the D.C. Department of Housing and Community Development, which oversees the program. “It’s not the only tool. It’s not the only solution. But it’s part of it.”