MacDonald-Miller Facility Solutions proudly celebrates BNBuilders Headquarters, recognized with two 2025 Awards of Merit from ENR Northwest for Excellence in Sustainability and Renovation/Restoration. This adaptive reuse project demonstrates how thoughtful renovation and sustainable mechanical design can breathe new life into historic structures while dramatically reducing environmental impact across the Pacific Northwest.

The dual recognition highlights a project that achieved an 83% reduction in embodied carbon compared with new construction and is expected to earn Zero Carbon certification from the International Living Future Institute. The project earned a Fitwel 2-star certification in May 2025 and a LEED Gold certification in September 2025.

Why this ENR Award-Winning Project Stands Out

• Historic preservation with modern performance: This 28,000-sq-ft renovation of Seattle’s historic Ainsworth & Dunn building, originally built in 1902 as a salmon processing warehouse, preserved nearly all of the original envelope, structure, brick exterior, and heavy timber framing while adapting it into a modern, collaborative workspace.
• Exceptional carbon reduction: An 83% reduction in embodied carbon compared with new construction, positioning the project to achieve Zero Carbon certification from the International Living Future Institute.
• Sustainable mechanical engineering: MacDonald-Miller’s scope included new fan coils, piping, and ductwork designed for an open ceiling layout, plus a Zero Carbon Feasibility Study by MacDonald-Miller Engineering that informed sustainable strategies throughout the project.

MacDonald-Miller’s Role: Mechanical Engineering for Sustainable Adaptive Reuse

MacDonald-Miller partnered with BNBuilders to deliver mechanical systems that support occupant comfort, indoor air quality, and long-term energy performance while respecting the building’s historic character. Our scope included:

• • HVAC Design & Installation: New fan coils, piping, and ductwork designed specifically for an open ceiling layout that showcases the preserved heavy timber framing.
  • Zero Carbon Feasibility Study: MacDonald-Miller Engineering provided critical analysis that informed sustainable strategies and helped the project target Zero Carbon certification. Energy Assessments, including the Zero Carbon Feasibility Study, help customers set climate goals with confidence, pursue certifications, and plan meaningful building upgrades. Based on the existing equipment and new HVAC & Plumbing System Design, our study showed that over 30% reduction in modeled operational energy use is achievable. Combined with purchased offsets through Seattle City Light, the project is positioned to achieve Zero Carbon certification. The building is currently in its performance period, tracking modeled energy results against real annual energy use.
  • Systems Integration: Mechanical solutions that balance modern performance requirements with the constraints and opportunities of adaptive reuse.

From preconstruction planning to final commissioning, our focus remained consistent: quality craftsmanship, sustainable design, and systems that enhance both building performance and occupant comfort.

See more: BNB Headquarters project