Denny Park Apartments is a 55,000 square foot, 6 storey, mixed-use building in Seattle’s South Lake Union neighborhood. The goal of Denny Park is to meet a growing need for affordable housing downtown and promote economic sustainability and livable neighborhoods.

Fifty dwelling units above street level commercial space serve households at 30%, 50% and 60% of the median income, including eight transitional housing units for homeless families with children. There is a mix of studios, one, two and three bedroom units as well as a common room with kitchenette adjacent to a courtyard.

An initial “green charrette” was held with the entire design team, including the owner and the general contractor, to identify sustainable design goals for the project and how to achieve them efficiently. The team included several LEED-accredited members, as well as representatives from Seattle City Light, the Seattle Office of Housing, and an outside consultant from the Lighting Design Lab. The project also went through the city’s design review process, which gave the public and neighborhood organizations the opportunity to influence design. The main challenge was to maximize residential density and minimize building area given to parking. Pedestrian-friendliness was prioritized, with glass canopies and sidewalk planters enhancing outdoor areas. The planters also contain structural soil allowing groundwater to recharge. Bicycle racks encourage bicycle use. Parking has been minimized to encourage alternative transportation, made feasible by proximity to transit. Located on a quiet street that dead-ends at Denny Park, the site is well served by several bus routes within 800 feet, each route providing service at least 5 times per hour during peak hours. Only 30 residential parking stalls and 5 commercial stalls are provided.

Denny Park Apartments sets an example for affordable and sustainably designed housing in a rapidly gentrifying neighborhood. The building uses interesting forms and colors to buck the stereotypical image of low-income housing. Avoiding mimicry, the design recalls the industrial history of the neighborhood while evoking a residential nature: a saw-tooth roof-form is reinterpreted as dormers; silver corrugated metal siding emphasizes bay windows. The ground floor responds to the urban fabric with zero-lot line development and commercial uses, while the massing of the upper residential floors sensitively avoids crowding the neighboring church by providing a courtyard as a buffer. Among other sustainable design features, the project showcases stormwater planters, the first to be built in Seattle for stormwater retention. These required close collaboration between the design team and Seattle Public Utilities and Department of Transportation.

The non-profit developer of the project is committed to maintaining Denny Park Apartments as affordable housing for the life of the building. Therefore, durable materials were very important. The project uses 50-year materials such as metal siding, standing seam metal roofing, fibercement siding and concrete. Durable precast concrete pavers were used for the raised courtyard and smaller balconies are made of durable recycled plastic/wood composite decking. Siding was installed on a rainscreen system over Typar building paper. Metal roofing was installed above highly permeable polypropylene Roofshield, a product that keeps moisture out while allowing the roof to breathe, maximizing the life of the wood frame structure. Indoor air quality was a high priority as well when considering the life of the building. Carpets are Carpet and Rug Institute (CRI) Green Label indoor air quality certified, paints are Master Painters Institute (MPI) "Green-Performance” certified, and sealants are all low-toxic and low-VOC. Countertops are made from formaldehyde-free wheat fiber particleboard. Continuously-operating whole house fans draw in fresh air and smoking is not allowed in the building.

The overall massing of Denny Park is oriented along an east-west axis. Large windows maximize daylighting in this cloudy climate, including in the corridor. To avoid the effect of urban heat islands, metal roofing that meets EnergyStar "cool roof" criteria was selected and sloped to direct rainwater to large stormwater planters. A mix of drainage aggregate and organic soil was engineered to achieve specific percolation rates. The native plants selected are suitable for stormwater retention yet are drought-tolerant. Drip irrigation uses 32% less water than a conventional spray system. Inside, NAHB-tested low-flow toilets. EnergyStar dishwashers and front-loading clothes washers promote water conservation.

Early in schematic design, an energy life cycle cost analysis (LCCA) was done to determine the most appropriate system for heat and domestic hot water for the residential portion of this building. The typical first cost-driven solution for multi-family residential projects in the Northwest results in electric resistance heat and individual electric hot water tanks, which consume the most source energy and have the shortest life span. Following the LCCA, a central natural gas hydronic heat system and hot water system were designed, which consume the least amount of source energy while providing a longer lifespan. Through the design development process, further efficiencies were added: ultra-high efficient 95% Rheem-Rudd Advantage water heaters (95%) and Munchkin condensing boilers with an AFUE of 93%. In addition, light fixtures throughout Denny Park are EnergyStar fluorescent, with occupancy sensors in common areas. The thermal envelope was improved 17% beyond code requirements with intermediate framing which differs from standard framing in that corners are formed with 2 studs, rather than 3 studs, avoiding uninsulated pockets. In addition, all the wood headers are insulated with R-10 rigid insulation. To minimize infiltration the airtight drywall approach was used.

Products used containing recycled content were as follows: drywall (12%), batt insulation (25%), concrete (18% fly ash), vinyl flooring (23%), acoustic ceiling tile (ACT) (78%), light gauge steel (27%), and plastic/wood decking (76-100%). Recycled glass cullet and recycled concrete were used for fill below slab-on-grade and backfill. No chromated copper arsenate (CCA) was used. ACQ (Alkaline Copper Quat) was used as a wood preservative instead, which is arsenic-free and chromium-free. A construction jobsite recycling plan was implemented with wood-only dumpsters, cardboard-only dumpsters, and commingled dumpsters. Drywall scraps were recycled, as were materials from the demolition of the previous building. Overall, 90.75% of construction waste was diverted to recycling. To reduce waste, lumber and engineered wood were cut to length by the mill before shipping, and walls were panelized.

Training sessions with maintenance staff emphasize sustainable design aspects. Upon move-in, each resident is given a welcome kit, with environmentally-friendly cleaning products and a description of the sustainable design features of their home.

Denny Park Apartments participated in the Seattle Built Green program (3-star) and Built Smart, administered by the City of Seattle's electric utility, Seattle City Light. The project satisfies 159 different items on the Seattle BuiltGreen Certification Checklist for sustainable design. The project is also the City Office of Housing’s ninth SeaGreen project, an initiative promoting healthy environments while protecting and conserving resources. It was the first project to receive funding under the Green Communities Initiative, a five-year, $550 million commitment to build more than 8,500 environmentally friendly affordable homes across the country sponsored by Enterprise Community Partners, Inc., the American Planning Association, the Natural Resources Defense Council, the AIA and others.