SEATTLE — For Denis Hayes, president and CEO of the Bullitt Foundation, the best way to advance a cause is by pushing the envelope. The Bullitt center, slated for completion before the end of the year, is what he calls, “A bold attempt to do everything right.”
By “everything” he means every phase of the project, from design and construction, operation and maintenance, right up to its eventual demolition (projected more than 250 years out) is intended to push the leading edge of performance-based design. Features of the building include net-zero energy, net-zero water and onsite sewage and wastewater treatment.
PAE Consulting was chosen to design and install the mechanical systems for the center and began work in late 2009. PAE has offices in both Seattle and San Francisco employing more than 60 people. The firm has made sustainability and energy-efficiency mainstays of their work, according to Marc P. Brune, an Associate with PAE and lead project engineer for the Bullitt Center.
“Our company president [and Bullitt Center PM] Paul Schwer met with their president, Denis Hayes and they both hit it off,” Brune explained. “They share the same vision.”
The 30-million dollar, 50,000-sq. ft. commercial building is heated and cooled by radiant flooring, powered by a closed-loop geothermal system. A specialty geothermal contractor — Geotility — dug 26,500-ft. deep wells. One-inch polyethylene tube goes down the wells and then feeds back up into the mechanical room where four water-to-water heat pumps make the energy exchange from the well side to the building side.
The heat pumps then deliver either hot water or chilled water. “That changeover happens seasonally,” Brune said. “The building is essentially in all-heating or all-cooling mode at any given time.”
To maximize energy efficiency, the building was designed to work in conjunction with Seattle’s mild climate. “The cooling set-point is 80 degrees,” Brune said, “and we think it’s only going to hit that perhaps 20 hours out of the year.” Windows in the building are automatically opened if it’s greater than 65 degrees outside, while greater than 80 degrees inside. Based on their analysis, PAE predicts sufficient geothermal capacity to handle Seattle’s coldest days.
The radiant PEX tubing is set in a 3-in. poured topping slab. A pump in the mechanical room circulates through the main loop, and each floor has four manifolds. “We laid it out so that each of those loops can become an individual zone,” Brune said, the thinking being that future tenants might want to partition certain areas and have them individually controlled.
(Electricity for the pumps and manifolds — in fact all electrical power for the entire building, including lighting — comes from a 14,303-sq. ft., 242 Kw photovoltaic array on the roof.)
Potable water comes from a 56,000-gal. cistern in the basement that will harvest rainwater from rooftop catchments. Net-zero water usage is a key goal of the Bullitt Center. Right now, the right to use rainwater in potable applications is one of the court hurdles the building still needs to overcome.
A city water line will be connected and feed to the fixtures, however, “Once the rules get figured out,” Brune said, “and the health department signs off on it, then the system will be cut off from the city water lines.” The intent is to use filters and chlorination to make the cistern water every bit as safe as city water.
In an effort to conserve water all fixtures and toilets — which have yet to be installed — will be low-flow. All toilets in the building are composting. “Everything gets sent down to the basement,” Brune said, “where there are composting units that break down the compost so a contractor can come and haul it away.” The centralized system connects several toilets to a single composter via a large chase.
Wastewater is being treated on-site as well. It will go through a series of filters and then into a constructed wetland that is part of the building’s green roof system.
The project has been a series of challenges from first to last, most involving the balance between the energy the building uses vs. the energy the building generates. But Brune believes that encountering and solving these types of problems is a large part of what the project was all about.
“It’s something for everyone, the design team, the design community and the greater community to learn from,” he said, “from the places we ran into difficulties and the solutions we came up with, so someone else can build a building like this and not have to worry about the same things we did.”
To help consolidate those lessons, the first floor of the Bullitt Center will house the Center for Energy & Urban Ecology. Programmed by nonprofit and public agency partners including the University of Washington’s College of Built Environments, it will feature an open resource library, classrooms and exhibition space.