Carbon12 is a wooden building located in the Eliot neighborhood of Portland, Oregon, in the United States. This eight-story structure was built using cross-laminated timber (CLT) made in Oregon. When it was completed, it became the tallest wooden building in the United States.
Carbon12 is an 85-foot (26-meter) mixed-use building located at the corner of North Williams Avenue and 12 Northeast Fremont Street. It was designed, developed, and built by Ben Kaiser of PATH Architecture and Kaiser Group Inc. The building uses CLT panels created by Structurlam. The rooftop deck adds 10 feet (3 meters) to the building’s height, making it 95 feet (29 meters) tall. Construction began in July 2016 and was finished in 2018. The name "Carbon12" comes from the atomic weight of carbon (12 AMU) and the building’s street address (12 NE Fremont St.). The use of timber was influenced by the goal of reducing the building’s carbon footprint. It is said to be one of the most efficient and environmentally friendly wooden buildings in the United States.
History
In many countries, using timber frames to build 1-2 story buildings is common. However, for many years, old building rules in the United States limited the use of wood in buildings with 5 or more floors. As science and construction methods improved, new wood products were created that are stronger than steel and more fire-resistant than needed for US building codes. These improvements, along with examples of tall wood buildings in Europe, have helped the US accept wood in construction. New building rules are now being considered to allow this.
The Carbon12 building entered the USDA's Tall Wood Buildings contest in 2014 but did not win. However, the company Kaieser+Path decided to build it anyway because they owned the land, which was a contest requirement. This building followed the 2015 International Building Code (IBC) under Type III-A construction, which allows wood buildings up to six stories tall (85 feet). The designers planned for eight stories, which caused delays and extra costs because the City of Portland had never reviewed a tall CLT project before. Eventually, city and state officials allowed the building to use special materials and methods under IBC section 104.11. They checked the building's safety and structure through a detailed analysis. Oregon Governor Kate Brown was present when the building reached its highest point. The Carbon12 building is seen as helping support Oregon's timber industry.
As wood construction becomes more popular, the Carbon12 building's title as the tallest wood building in the US is now being challenged by a 148-foot (45-meter), 11-story wood-framing building in Portland called Framework. This building is part of a USDA-winning proposal and is currently under construction.
Building details
The building is 85 feet (26 meters) tall and has 8 floors. There are two retail spaces on the ground floor, which are located below 14 condominium units (2 units per floor). Each unit has a recessed balcony and a separate elevator entrance. The building uses an underground automated parking system that moves cars to their parking spots using a conveyor system controlled remotely. The structure uses mass timber, glued laminated timber (glulam), and cross-laminated timber (CLT) for its framework. Steel is used in the building’s core and for connecting supports, and concrete is used in the basement, ground floor, and garage (automated garage).
The residences are 1,600 square feet and are made mostly of wood. They have large windows that reach from floor to ceiling, open floor plans, seismic alarm systems, and spacious patios. There are no shared walls between units, which provides sound insulation similar to living in a single-family home.
Residents of the Carbon12 have described the building as "beautiful" and "bright." Some residents were happy with savings on utility bills and commuting costs. Others praised the building’s universal design, which helps individuals who might otherwise struggle to access parts of a building or their home.
Carbon12 uses sustainably harvested and certified CLT, a renewable material that stores carbon, insulates naturally, and reduces noise and heat loss. The building’s CLT, glulam columns, and beams stored 132 tons of carbon. Exposed wood interiors create a connection to nature, and timber’s ability to char provides natural fire protection. The building also uses a buckling-restrained brace frame system to withstand earthquakes or other natural disasters.
The building’s design is environmentally friendly. It uses insulated fiberglass windows that reduce heat loss and maximize natural light. Common areas have efficient LED lighting systems with remote controls and sensors. Solar panels on the roof provide hot water and exterior lighting, reducing fossil fuel use and lowering greenhouse gas emissions and utility bills. The building’s exterior is covered with vertical metal panels and has a deep cut in the façade to allow sunlight into the central spaces.
Carbon12 uses an electric LG Variable Refrigerant Flow (VRF) system, which shares cooling and heating loads efficiently. Construction waste was minimized due to modular building methods and was recycled as biofuel.
Construction
The building was built by PATH + Kaiser group from Portland, which also worked on the Radiator building in Oregon, a mass timber structure. Munzing structural engineering, LLC helped create the best ways to combine steel and wood systems in the building.
The main structure is made of CLT, which was produced at Structurlam's facilities in Penticton, British Columbia. CLT is created by gluing many layers of wood boards together at right angles to make the structure stronger in all directions. These large panels can be up to 12 feet wide and 60 feet long. Glulam beams and columns were made using a computer-controlled process based on a 3D design model. Before making the mass timber, Kaiser+Path created a small model of the Carbon12 cross-section to test the design, how it would be built, and how it could be moved. When the model arrived at the site, it was put in place and checked. It also helped determine the exact measurements needed for a proper fit. After the foundation was built, a steel frame was set up for two floors, and timber parts were attached to it. The work was carefully planned. When materials arrived by truck, Glulam beams, columns, and CrossLam panels were lifted directly from the truck into place by a tower crane. Each piece was labeled and assigned to a specific spot in the building. Because most parts were made off-site, few workers were needed, which reduced costs, improved safety, and made the work more organized. Construction was completed quickly, and less waste was seen because of the prefabricated and modular setup. Each floor took about five days to build. CLT is expensive, but savings were made because of the fast construction and less waste.
Mass timber can be used in any weather. However, when it rained for several weeks, breathable SBS sheets were placed, and fans were used to warm the air and lower the moisture in the CLT to safe levels.
To meet sound requirements, a mix of materials was used for the acoustic system. Kaiser+Path hired different subcontractors to install insulation, a base layer, a gypsum concrete top layer, and finished floor products.
Carbon12 was built using a design-build method with subcontractors for the Mechanical, Electrical, Plumbing, and Fire systems (MEPF). These subcontractors were involved early in the planning process, which helped them create a plan for installing their systems without slowing other work. Because each floor was the same, improvements were made as the project continued.
The 2015 Oregon building code did not include rules for tall timber buildings (8 stories). To show the building was safe, designers used computer simulations and models. Sensors were also placed under the building to monitor its performance.
Recognition and legacy
In February 2019, Carbon12 received the 2019 Wood Design Awards for Best multi-family wood design, given by Woodworks. In 2017, the building was highlighted in the Portland Business Journal and Daily Journal of Commerce as the year's notable project.
Because Carbon12 was approved under special rules, its performance is tracked by the Colorado School of Mines. This engineering data helped change the 2021 IBC code to allow buildings with up to 18 stories. The firm is now working on The Spar, a project aiming to become the tallest mass timber building worldwide, with 36 stories and nearly 600,000 square feet of office and commercial space.