Seattle, Washington, USA
Seattle-based atelierjones has completed a an innovative, first-of-its-type, 8-story, 67,500 square-feet, mass timber middle-income housing project following all sustainable pathways within architecture and minimizing its operational carbon.
Named Heartwood, the building is owned and operated by Community Roots Housing, a local non-profit, affordable housing organization.
For its sustainable design, the project has been awarded a 2024 Green Good Design Award by The Chicago Athenaeum: Museum of Architecture and Design and The European Centre for Architecture Art Design and Urban Studies.
The 13 one-bedroom and 113 studio units average 400 square feet and feature exposed wood ceilings, columns, and beams with simple finishes to balance the warmth of the wood.
The building is exemplary due to its being one of the first Tall Timber buildings in North America, and the first tall mass timber workforce housing project in the US. Heartwood embraces a holistically sustainable approach throughout its design.
Located in a dense and transit-rich neighborhood with ample access to parks and essential services, it supports car-free, healthy living.
Mass timber is an engineered wood product made of lumber, laminated to create large panels, columns, and beams to be used as lower-carbon tall building structure.
Mass timber reduces the carbon impact of buildings in a few keyways. In Heartwood, the raw material is sourced within the Cascadia wood basket and manufactured and fabricated locally, reducing transportation, supporting rural economies, and economizing sustainable forest management.
The quantity of timber also sequesters large amounts of carbon and stores it for the life of the building and beyond.
Heartwood’s superstructure was determined to be carbon net-negative by a comprehensive life-cycle analysis performed in partnership with the University of Washington.
Heartwood is one of the first realizations of the major Tall Timber code updates to the International Building Code written in part by the Architect’s Founder and Principal Architect from 2016 to 2019.
The 2018 code revisions introduced three new tall-timber building types, of which Heartwood is the first Type IV-C building constructed in the US.
Years of fire testing and research went into the code revision process to prove that mass timber is a demonstrably safe and sustainable building alternative, but the code remained untested in practice and execution.
Heartwood required the team to work closely with local officials to interpret the language and intent of the codes.
The structure primarily consists of cross-laminated timber (CLT) floor panels on glue-laminated columns and beams with a steel buckling-restrained-braced-frame at its core to resist earthquakes.
The lighter-weight wood structure reduced the quantity of carbon-intensive concrete required in the foundations significantly as compared to concrete equivalents.
The 2-hour fire-rated all-wood joint utilized at column to beam connections, remove a significant quantity.
Project: Heartwood
Architects: atelierjones LLC.
General Contractor: Swinerton, Inc.
Owner’s Representative: Lineage Real Estate
Developers: SkipStone
Client: Community Roots Housing
Photographers: Laura Swimmer
