909 Walnut

FROM THE ARCHITECTS:

On one of Downtown Boulder’s last remaining infill sites at 909 Walnut Street, the property owners envisioned an “exemplary” project that would meet their commercial objectives for a sustainable, mixed-use building and the aesthetic demands of the area’s turn-of-the-20th-century context. To realize the solution, they turned to Denver and Boulder architecture firm Arch11 for its artful approach to blending the old and new in a way that acknowledges the surrounding history and invigorates the urban fabric.

The completed 909 Walnut building consists of a new three-story structure with two floors of offices above a ground floor restaurant. The design references the height and proportions of its masonry neighbors while establishing its own presence in Boulder’s iconic low-rise commercial cityscape.

In response to the solidity of the buildings that bookend the site, Arch11’s Principal E.J. Meade and Architect Kimball Hobbs realized early on in the process that to maintain the streetscape’s integrity, less would be more. Working within the City of Boulder’s Downtown Urban Design Guidelines and stringent zoning regulations for building height, setbacks, bulk plane and open space, they manipulated the buildable volume to optimize square footage and also provide daylight deep into the 14,475-square-foot structure.

By slipping the ground floor restaurant space and upper floor office levels forward and backward in section, Arch11 generated a protected outdoor seating area for the restaurant’s patio and sun-filled rooftop deck. Light scoops on the east and west sides of the building – areas where no windows were permitted – deliver added daylight to the second and third floor offices and entry lobby.

To shade the south facing glass along the street front, Arch11 suspended a slender brise-soleil made from terracotta “baguettes” from the building’s structure. The delicately proportioned screening device serves to both shade the interiors and maintain the established building edge along the sidewalk. With proportions matching those on adjacent buildings, “windows” are subtracted from the continuous sun screen to provide light and views from within and to emulate the deep “punched” openings found in Boulder’s masonry-clad downtown district.

“During the day the screen reads more solid than at night when the light comes from within the building,” explains Arch11 principal E.J. Meade of the shape-shifting façade. “From the outset,” he adds, “one of our goals was to provide an urban response that maximizes transparency and resists the solidity of the masonry structures on the block.”

Although they didn’t design the tenants’ interiors, Arch11 created an architectural setting that establishes a strong relationship between the spatial and tectonic layering of the façade and the spaces inside. Within the lobby for example, details like the wood stairs and metal railings are “articulated as discrete parts” – each contributing to the minimalist composition that ties the interior to the striking street façade.

While the owners chose not to pursue LEED or other green building certifications, they were committed to sustainable design, which Arch11 emphasized throughout. Operable windows were specified to facilitate natural ventilation, a solar thermal system heats water, and high-efficiency lighting as well as the daylighting deep into the building’s core are energy savers. The exterior terracotta sunscreen tempers southern light and roof overhangs are calibrated for summer and winter sun angles. Overall, the building’s energy performance is projected to be 43 percent better than a baseline building of similar size and location.

Arch 11 / 909 Walnut St / Boulder, CO from Astula Inc on Vimeo.