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June 29, 2017

The story behind — and beneath — those big vent stacks

  • The two tall stacks were positioned to preserve good air quality and views of Elliott Bay.


    Pike Place Market draws 10 million visitors a year, but it is not just a destination on a sightseeing itinerary. It’s also very much a piece of the city’s social infrastructure, with mixed-income and affordable housing, child- and elder-care facilities, a medical clinic and a food bank all part of the 9-acre site.

    This was an important factor that Arup, a global engineering and consulting firm with an office in Seattle, took into consideration when it joined the design team for the new MarketFront complex. The firm had to keep the longevity and adaptability of the Market spaces top of mind as it planned systems for a site that was tightly bordered by buildings on the north and south sides.

    Carefully placed stacks

    What visitors don’t see may be one of the most challenging parts of the MarketFront story: Arup connected the site to the Market’s central plant, designing the building around the existing cooling towers while keeping the plant — which serves the entire Market — in operation. Now the plant serves the new building, too.

    The team sought to leverage the plant’s heat recovery capabilities to minimize future operating costs. However, the existing plant was located on the site, so the team had to accommodate it in the building footprint and figure out a way to vent the exhaust. To achieve this, Arup provided specialist structural services to engineer tall vent stacks that carry the exhaust up away from the public spaces.

    Photo courtesy of Arup [enlarge]
    The vent stacks — 51 and 37 feet high — carry exhaust away from public spaces.

    It’s a community-conscious solution to multiple design problems. The stacks have been carefully placed to preserve the view corridors to Elliott Bay that occupants of the nearby residential units enjoy. They have also been sized to ensure a healthy environment for the public.

    One stack stands 37 feet tall, and the other rises 51 feet from the top of the fluid cooler. Both open 25 feet above neighboring homes, businesses and public areas to ensure air quality.

    The services within the building are designed to be energy efficient and to allow for additional equipment to be installed later if needed.

    Arup conducted energy modeling studies, produced a measurement and verification plan, and increased the ventilation performance of the system, all which contribute to the project’s eligibility for the U.S. Green Building Council’s LEED program.

    MarketFront is targeting LEED gold certification. Other new design features that contribute to the LEED goals include LED lighting in the parking garage and infrastructure for electric car charging stations.

    Maintaining authenticity

    One of the appealing characteristics of the Market is its architectural authenticity. Any historical artifice or contemporary detail would appear out of place at the Market, which has been a working commerce center since 1907.

    To tie in with the Market’s industrial aesthetic, Arup worked closely with Seattle architects Miller Hull Partnership on the design of armatures that organize the various services that need to exhaust or vent up through the roof and extend above the vendor area. The armatures both protect and reveal the myriad ducts and vents, establishing an “organized chaos” aesthetic that is true to the Market’s nature.

    Arup is a participant in the Global Designing Cities Initiative, which shares best practices in promoting public health and safety, quality of life, multimodal mobility, economic development, environmental sustainability and equity in the design of urban centers.

    By the time the firm completed its work on the MarketFront project, several of its staff had become actively engaged with the various social services and causes at the Market, realizing the investment they had made at the outset of the project to understand, learn from and respect the needs of the downtown community.

    Cress Wakefield is an associate and senior electrical engineer in the Seattle office of Arup. She was Arup’s multidisciplinary project manager and lead electrical engineer for MarketFront.


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