Why Climate Activists Are Interested In Accessory Dwelling Units

climate aduClimate activists all over the country have been advocating for ways to limit the environmental crisis. One of those ways is to implement more accessory dwelling units (ADUs) in larger cities. You might know ADUs by other names — like mother-in-law apartments, granny flats or secondary dwelling units.

These homes provide a less detrimental environmental impact and affordable housing. Here’s more on why climate activists are interested in changing zoning requirements for accessory dwelling units.

What is an Accessory Dwelling Unit?

ADUs, short for “accessory dwelling units,” are housing options built right on the site of a single-family house. These units can be dwellings like apartments over a garage, a basement apartment or a tiny house in the backyard or side yard.

ADUs, no matter the type, are always on the same property as the primary house. It comes directly with the house — so when the house is sold or bought, the ADU cannot be sold or purchased separately. They have one owner, except in rare circumstances.

The name might make sense now. The dwelling unit is like an accessory to the main house. They’re currently on a popularity rise for a number of factors including affordability and climate considerations.

Why Are They Being Advocated For?

ADUs are great for either renting out to gain extra money or housing a family member, like a grandmother or college student. They’re a good solution for families who enjoy multigenerational housing, particularly in regards to childcare. For other households, renting them out can help homeowners manage mortgage payments over time and provide two housing options for just one lot.

Now more than ever, though, ADUs are being advocated for by climate activists. Since these homes are so small, they’re energy-efficient. They can cut CO2 emissions by almost 40% over a lifetime compared to the traditional family home. They also provide much-needed housing without creating the need to develop and build on new lots.

Each accessory dwelling unit is full of everything someone needs to live, including a full kitchen, bath and their own front entrance. A majority of the population doesn’t need the size of home they might be living in right now, and some are looking for small houses that are hard to find in the existing real estate market.

The differences in climate impact come primarily through energy needs. A smaller home takes less time to heat up or cool down, uses less water, doesn’t need as many lights, and so on. Additionally, energy is saved through the transport and fabrication of materials.

Better yet, small homes are more environmentally-friendly than homes built with green construction practices. Over a lifetime, a small home generates significantly less energy than a standard home.

Policies for Accessory Dwelling Units

Although ADUs are great for the environment, the economy and families, there are sometimes strict policies in place if you want to add one to your home. Yet, those policies have been loosened in some areas, which is why the tiny house is trending.

ADUs are most popular in highly populated areas, stretching from Washington, D.C., to California. However, they are still seen in suburban and rural areas. If you’re interested in the changing policies, check out these examples from around the United States:


California has had a housing and affordability crisis for years. Many people struggle to find a home they can afford. However, the housing shortage changed not long ago.

A new bill allowed Californians to implement accessory dwelling units in their single-family homes. Those who already owned homes could build an ADU over their garage as a small apartment or create a completely separate tiny house in their backyard. Some Californians were able to add both, transforming their homes into a triplex.

If people continue to obtain permits to build ADUs, it can play a part in addressing the housing crisis. There is hope that more will be constructed in the larger cities like Los Angeles, San Diego and San Jose.


In 2019, Seattle, Washington, took a step forward in the housing market by allowing residents to add accessory dwelling units to their homes easily. Instead of the land being used for standard home residencies, legislation permitted 75% of the reserved land for ADUs, making the city greener and adding affordable housing.

The new policy allows residents in single-family homes to add up to two ADUs, and it puts a size limit on new homes.

Additionally, Seattle got rid of parking quotas and requirements that the owner lives on-site. This made the city greener and provided more housing for those with lower incomes.


The Twin Cities also jumped on the bandwagon and changed their policies regarding ADUs. Affordability for housing in the region was worsening, but ADUs presented a solution to the housing needs. In 2019, the area permitted nearly 140 new units, and residents can now turn their property into triplexes.

Legislation has changed zoning laws, which allows for a greener place to live, and it has proven to shrink the gap in racial disparities because of new, affordable housing.

Green and Affordable Housing

As more cities around the country adopt legislation to allow accessory dwelling units, you’ll see an increase in affordable housing and an increase in green housing. ADUs are a great solution to the housing crisis and have a smaller environmental footprint on the earth.

So when will you add an ADU to your home — or live in one yourself?

Evelyn Long is the editor-in-chief of Renovated, where she publishes home renovation and construction ideas to create more sustainable buildings.