Owners of income-restricted buildings in Dorchester and Mattapan will be able to apply for up to $50,000 per unit for “deep energy retrofits” as part of the Wu administration’s efforts to cut back on greenhouse-gas emissions and lower costs.

Roughly 50 percent of greenhouse-gas emissions from Boston buildings come from residences. According to the Wu administration, helping buildings become more energy efficient will lead to lower energy costs for tenants while improving indoor air quality.

The mayor’s housing office is also offering up to $10,000 in technical assistance to support building owners seeking to figure out their energy usage and find ways to get a “deep energy retrofit.”

Retrofits can include installing energy-efficient lighting and appliances, upgrading insulation that stops heat loss, and replacing heating, ventilation, and air conditioning (HVAC) systems with more efficient models. Solar panels and upgrades to windows and doors are also on the list.

The initiative, called the “Large Building Green Energy Retrofits Program,” is part of a $20 million effort that is funded through federal recovery money and focused on the city’s existing housing stock. The $20 million program also includes a parallel effort on affordable housing in three-deckers, an iconic three-family home found in Dorchester, Mattapan, and other Boston neighborhoods.

The Wu administration is working to develop program guidelines and is aiming for an announcement in the spring or summer, when the city can partner with interested and eligible building owners, according to a spokesman.

Meanwhile, the retrofits grants, which Mayor Wu announced in Allston-Brighton last week, are targeted toward building owners with 15 units or more. Dorchester and Mattapan buildings in the following ZIP codes can apply: 02121, 02122, 02124, 02125 and 02126.

The new program “is a comprehensive effort to improve the energy efficiency and environmental sustainability of existing affordable housing in the City of Boston,” Sheila Dillon, Wu’s chief of housing, said in a statement. “By investing in green energy retrofits in income-restricted housing, we are creating a more sustainable and resilient city. The changes this program will fund will reduce greenhouse gas emissions, contribute to a cleaner, healthier city and will advance Boston’s goal of achieving net-zero emissions by 2050.”

City officials have put out a request for proposals (RFP) that laid out eligibility guidelines, saying the properties must “amount to at least 15 units located within the same market area and will be owned by the same entity.” The owners’ proposals for retrofitting the units “may include a single building or multiple buildings as small as 2 units in order to achieve the proposed total number of units,” the document said.

Vacant properties may be considered on a case-by-case basis.

The program “is designed to take advantage of opportunities that exist to achieve deep energy retrofits of existing housing that is already providing adequate housing at reasonable rents,” the RFP said. “It is also designed to minimize the impacts on current tenants, including limiting relocations to the shortest duration possible or even completing all work without any relocations.”

The buildings can house people with a mix of incomes, “but at least 50 percent of the units in a proposed retrofit project must be restricted to tenants that earn no more than 60 percent of the Area Median Income (AMI),” the RFP added.

The federal funds come with some strings attached: They must be spent by Dec. 31, 2026, under timelines set up under the American Rescue Plan Act (ARPA).

At the same Allston-Brighton event last Thursday (March 16), held at the Brian Honan Apartments, Wu and other city officials pitched a “green” building code through a new ordinance proposal that needs the approval of the City Council, and would go into effect in 2024.

The code calls for buildings that use fossil fuels to add “wiring for future conversion to electrification” and install solar energy features.

In 2021, the City Council passed, and acting mayor Kim Janey signed, the Building Emissions Reduction and Disclosure Ordinance (BERDO) in 2021. It requires existing buildings, which come to greater or are equal to 20,000 square feet, to reduce emissions to net-zero by 2050.

Separately, Wu is pushing for Boston to get permission from the state to set new standards that would ban the use of fossil fuels in new developments or major renovations. The pilot program is run by the state’s Department of Energy Resources.