Could Your Next Home be an ADU?

The building industry in general continues to design and construct homes that only meet the minimum code requirements, despite the fact that has gotten easier, less expensive, and more beneficial for homeowners to invest in more sustainable homes that are healthier and cost less to operate. Of the 115 million housing units across the United States, there are only an estimated 220,000 homes and multifamily units that are certified by either LEED, National Green Building Standard (NGBS), or other local building standards.

In the Pacific Northwest, though, sustainable construction is starting to dominate the market share. The State of Washington continually ranks among the top ten states for LEED certifications, and 38 percent of new home construction in Oregon qualified for a rebate from the Energy Trust of Oregon due to the implementation of energy efficiency measures. 

There are also dozens of architects, contractors, and builders that specialize in sustainable building in the region. (Check out Rise’s Home Pro section to find one!) Rise recently sat down to talk with Nick Mira, a LEED-accredited architect working with Propel Studio, an architectural firm in the Portland, Oregon area that specializes in Accessory Dwelling Units, known as ADUs. 

ADUs are basically additional “dwellings”—place to live—located on your property, such as basement apartments, a tiny house on your lot, or an apartment over your garage. They have been gaining traction in the marketplace as land values have increased and people look for more innovative, affordable ways to live.

Where did Propel Studios' passion for sustainable building originate?

Our health and wellbeing depend on the health of our planet, and we’d very much like to change the course that our planet is currently on. Once you know better, it’s painful not to do great work. It’s frustrating to know those proven ways to build homes that operate with net-zero energy exist, but see that most homes in America are still built to the lowest legal performance standards. We are always trying to push our clients to consider sustainable features whenever possible. 

Your firm specializes in building Accessory Dwelling Units (ADUs). In what way do ADUs contribute to sustainable living?

ADUs contribute to sustainable development by allowing more housing density closer to an urban center. This preserves the natural surroundings by limiting sprawl and reduces our city’s energy usage by reducing transportation and inefficiencies of sprawling utility networks. Further, it addresses social sustainability by providing new, relatively affordable housing in existing neighborhoods. It also helps people age in place and reduces displacement by giving some people the ability to earn income off the property they already own. 

Here in Portland, ADUs are definitely becoming more popular. When we started Propel, only a few people had built ADUs, and most people didn’t even know what they were. Over the past three years, we have seen permits for ADUs jump from a couple hundred per year to over 600 per year, and this trend is ongoing. 

As ADUs are being allowed in more and more jurisdictions, we find a common theme is that they are limited in size, so as to not overpower the original home or change the character of a neighborhood too much. This varies from allowing an ADU to be a certain percentage of the size of the main house (typically around 50%-75%) to having a maximum area (typically 700-1000 square feet). Because of this size constraint, ADUs challenge us to create houses that are much more efficient. Smaller appliances and bedrooms, more flexible open spaces, and vaulted ceilings are all things we consider. For reference, the average new home built in the US last year was around 2,500 square feet. Since ADUs are mostly under one third of that size, they can comfortably accommodate 2-4 people with much less energy used per square foot for heating (and in some cases cooling). They are a great option for many families with multiple generations.

Can you explain what the 2030 Challenge is and how it affects the buildings and homes you design?

The 2030 Challenge was created to end the pervasive use of fossil fuel energy sources to operate our buildings by the year 2030. This goal will be achieved by focusing on design strategies such as site location, solar orientation, passive heating and cooling, energy efficiency, and on-site renewable energy sources. Since only 20% of the energy used by a new building under the 2030 Challenge standards may come from green power purchasing (such as wind power from your utility company), 80% of the energy will need to be generated on-site. This puts a lot of focus on new thinking and custom, smart design solutions. We love the challenge and necessary changes this will encourage the future of our built environment.                   

Could you explain some of the main sustainability elements of the homes you design?

We find that everyone has a slightly different definition of sustainability. We include beauty in ours. We also try to focus on the basic sustainability principles first—those sustainable measures that have the biggest return on a project’s cost-benefits. We find these to be building orientation, passive solar heating/cooling, limited and strategic window placement, extra insulation, and durable materials. We want our projects to be super-insulated and airtight, with careful ventilation through energy recovery ventilators. We want to knock off the big payback items first, before recommending more expensive sustainable features, such as photovoltaic electric systems or solar hot water. 

We find it interesting that you also design the landscape around the home for maximum sustainability. Could you give us an idea of how you do that and why it is important?

We like to think of the entire landscape and building as the architecture and continue design elements inside and out. Whether viewed inside or out, using landscaping in conjunction with the interior building plan, we can enhance the experience of a home to add the feeling of comfort and wellbeing. This strategy can make spaces feel more spacious.

Another area we focus on when laying out a new home is site rainwater and the permeability of ground surfacing. As far as the management of stormwater goes, we design every project to keep rainwater on-site, allowing it to replenish our local aquifers. We can do this with the use of hidden underground dry wells, which are buried 5-10 foot deep concrete cylinders that inject stormwater back into the ground locally. On top of this, we like to add surface landscape features that catch and play with water, create a focal point, and celebrate our Pacific Northwest rainy climate. It’s fun to imagine new ways to play with water and showcase site water retention.  

One common assumption that many people have is that sustainable homes are also expensive homes. Do you agree with that?  

This depends on the timeframe you look at for costs. We educate and encourage our clients to think not only about initial construction costs, but also lifetime costs of operating that result from our design decisions. In every project, we recommend durable, low maintenance, and sustainable materials, like an exposed concrete floor slab, quartz countertops, and solid wood or tile baseboards. We strongly recommend fast payback sustainable features first. If the budget will allow, then we get into renewables.  

Any additional comments?

It frustrates me that we aren’t already designing to 2030 standards because we can! It does cost more (sometimes), but with virtually no heating/cooling / or electric bill for the life of the building, you’d think we’d already have new construction loan financing that recognizes and encourages sustainability, taking into consideration the life-cycle benefit.

Article by:

Tobias Roberts

Tobias runs an agroecology farm and a natural building collective in the mountains of El Salvador. He specializes in earthen construction methods and uses permaculture design methods to integrate structures into the sustainability of the landscape.