Who wins when it's green vs. green? In the case of Shoreline City Hall and Civic Center, everyone does, thanks to the Design/Build skills of MacDonald-Miller Facility Solutions, Seattle, WA.
The dueling greens on this project are probably quite familiar to Design/Build contractors: the desire for an environmentally friendly green building, coupled with a desire to save as many greenbacks as possible. Fortunately, as this project proves, the two are not mutually exclusive.
“The city insisted on high value and had a strict budget, yet also desired that the project showcase its commitment to green building,” says Jared Sheeks, project engineer, HVAC, MacDonald-Miller Facility Solutions. “We accomplished this by thoroughly analyzing each green measure for financial impact, and choosing measures with the highest value first.”
Shoreline City Hall is a four-story, 67,000 sq.ft. municipal headquarters. In addition to serving as a city hall, the building also serves as a civic center. Being at the heart of an urban revitalization project, the site was designed as a place for the city's residents to gather, and as a place for citizen involvement in city government.
Many Sustainable Features
The building includes four main floors of offices and an accessory council chambers wing. Sustainable features abound. Public restrooms in the building are equipped with water saving pint-flush urinals and low flow faucets. Covering the city council chambers is a green roof, accessible from the third floor. A super-insulated envelope reduces the heating and cooling load.
Shoreline City Hall is cooled and ventilated by two large rooftop air conditioners that deliver conditioned air to the main building and council chambers. Parallel fan-powered terminal units deliver air to the individual zones and are provided with electric heat. On the fourth floor, a server room is cooled with two rooftop packaged air conditioners. A central exhaust fan removes odors from the main restrooms, janitor rooms, shower facility, and copy room.
A+ for Energy Efficiency
Energy savings exceeded initial project goals. When compared to an ASHRAE 90.1 baseline, the building uses 25% less energy. It's also under review for LEED® Gold certification.
“In addition to providing a comfortable indoor environment, one of the principal goals for the mechanical system was energy efficiency. Coupling this with the project's strict budget provided a challenge,” Sheeks says. “Fortunately, the owner, also being the sole permanent tenant, had a long-term perspective with regard to the mechanical systems. This allowed the team to focus on total life cycle cost, and less on first cost than might have happened with a speculative developer.”
An additional boost to the project came when the local electric utility, Seattle City Light, became involved early on, with the goal of helping the city meet its energy efficiency goals.
“Because of this long-term focus and excellent owner involvement, decisions regarding the mechanical systems were able to be made based on detailed energy and cost analyses,” Sheeks says. “Seattle City Light also offered rebates for many energy efficient features, making them more affordable to the owner.”
A number of energy efficient features were incorporated into the design. These included:
- High insulation levels in the walls and roof
- Demand controlled ventilation for high occupancy areas using CO2 sensors
- Demand controlled ventilation for office areas using occupancy sensors
- Recovery of waste heat from the data center
- Parallel VAV terminal units
- Hot aisle/cold aisle separation in server room
- Lighting reduction with daylighting controls and occupancy sensors.
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Since the predominant energy use in the Pacific Northwest is heating, this building was designed to saves energy through reduction of the heating load. This is accomplished with a focus on the two largest sources of heating load: the building envelope and fresh air ventilation.
To reduce heating requirements from fresh air ventilation, the project incorporates demand-controlled ventilation in both high occupancy spaces, and normal office spaces. In the densely occupied spaces, such as the lobby, conference rooms, and council chambers, carbon dioxide sensors are used to precisely measure the amount of pollution in the air and adjust the ventilation levels accordingly. In the regular office spaces, occupancy sensors detect the presence of people and switch the ventilation off or on accordingly.
Heat Recovery, Solar Hot Water System
Other energy efficiency features include the data center heat recovery system, where waste heat from servers is rerouted to office zones when heating is required. This system uses a variable speed fan to extract hot air from the data center and convey it to a handful of VAV terminal units on the north perimeter of the building. A solar hot water system uses a rooftop collector to pre-heat water for the council chambers restrooms.
Parallel VAV boxes are used because of their efficiency in delivering conditioned air to the spaces. In the data center, cooling energy savings are achieved by separating the cool air delivered to the servers from the warm air discharged from them. Plastic curtains keep the two airstreams from mixing, thereby allowing a higher supply air temperature to be used for greater efficiency.
Each piece of equipment was commissioned individually to ensure that it operated as per the design intent. The MacDonald-Miller commissioning team worked side-by-side with a third-party commissioning agent to implement the project's commissioning plan. This written plan leaves no room for error and ensures that the building operates per the engineers' design intent and owner's desires.
“This project's priorities of high value and energy efficiency proved to be a challenge, but also one of the project's greatest successes. As the two priorities are often at odds with each other, striking a balance became necessary,” Sheeks says. “This was accomplished through detailed energy and financial analyses that gave the team an objective ranking of each energy conservation measure. Using accurate total cost data, the analyses gave the team a good idea of the relative value of each measure. The end result was that the owner's budget was spent as efficiently as possible, and money was not wasted on high cost systems that might not be high value, or may not function up to their potential in the Pacific Northwest climate.”
Where else but the Pacific Northwest's “Emerald City” would you expect to find such a peaceful coexistence of green and … green?
Winner at a Glance:
MacDonald-Miller Facility Solutions, Seattle, WA
Shoreline City Hall and Civic Center, Shoreline, WA
PRODUCT KEYS TO SUCCESS:
- 2 Trane IntelliPak II rooftop packaged air conditioning units
- 2 Trane Precedent server room air conditioning units
- 2 Data Air mini ceiling computer room units
- 60 Nailor D35 parallel fan powered terminal units
- Multiple Greenheck exhaust fans, motorized dampers, and fire/smoke dampers
- Siemens TALON controls
- Canariis duplex water booster pump
- A.O. Smith water heaters
- Zurn toilets and urinals
- Toto faucets