Building Integrity
According to the understanding of environmental performance for the design of high building performance development in the slides of Professor Lam, the total building performance and diagnostics should be considered from four perspectives including physiological, psychological, socialogical and economical aspects. In the following paragraphs, building details are designed from every perspective to achieve high building performance.
Materials
(1) No out-gassing materials
The Bullitt Center was designed to meet the rigorous requirements of the Living Building Challenge Standard 2.1.1, which requires that a building be net zero energy, net zero water, use non-toxic materials, provide a net increase of functional ecosystem area, enhance human health, contribute to social equity, and emphasize beauty.
To comply with this imperative requirement, the Bullitt Center team worked for more than two years identifying products that did not contain Red List chemicals [2]. The Materials Red List in the Living Building Challenge identifies 14 chemical categories that must be avoided in products used in the project and the Bullitt Center team worked for more than two years identifying products that did not contain Red List chemicals.
Ecosystem services applied in the Bullitt Center
Resource: Optimiing urban ecosystem services: the bullitt center case study [3]
(2) Fire resistive materials
The product list conducted by the team of the Bullitt Center has 48 divisions. Among them, there is one divison about fire supression, which means the mentioned products are fire safety.
The fire resistive materials applied in the Bullitt Center
Resource: Optimiing urban ecosystem services: the bullitt center case study [3]
The application of climate regulation in the Bullitt Center
Resource: Optimiing urban ecosystem services: the bullitt center case study [3]
(3) Weather-tightness
The climate regulation is also taken into consideration in choosing materials in the Bullitt Center.
(4) Structural Stability & Durability [4]
Much of the construction methods used in the Bullitt Center involved standard industry practices, but there were several approaches that were relatively special to the process. The Bullitt Foundation and Point 32 chose heavy-timber construction for its environmentally friendly qualities. The development team wanted to minimize the use of concrete due to the high amount of greenhouse gases associated with its production. In addition, every piece of wood in the structure has been certified by the Forest Stewardship Council.
The basement and first two floors are made of concrete, while the top four floors use both steel beams for lateral support, and heavy timber to support the gravity load. The timber beams support the entire weight of the three-inch-thick concrete floors and the six-inch-thick wood substructure. The radiant heating and cooling tubes running through the concrete make it unable to provide any of the building’s structural support.
To qualify as “heavy timber,” the beams were required to have a minimum thickness of six inches (measured in any direction) and columns were required to have a minimum dimension of eight inches. Both must retain their structural supportive capabilities in a fire for at least one hour.
One challenge involved finding methods that take into account the shrinkage and distortions of wood over time, especially at the places where beams and columns meet. The team created special steel connectors—called buckets— that secure the horizontal beams to the vertical columns and transfer the weight from one to the other. Due to differences in the lengths of columns and beams, as well as the angle between the two, most of the connections between beam and column required a bucket specifically designed for that connection.
The heavy timber in the building itself serves as a carbon sink (instead of a carbon source, like cement), and new trees planted in place of the old ones now continue the task of removing carbon from the air. In compliance with Red List limitations, all of the timber is minimally treated and no toxic substances were used in treating the timber.
The application of heavy-timber framing in the Bullitt Center
Mechanical Management System
The machine rooms of the Bullitt Center are opened to visitors, which show the well-management of mechanical equipments.
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The machine rooms of the Bullitt Center
Lighting Connectivity
(1) Tall windows and narrow floor plans for daylighting
Since the weather in Seattle is always cloudy and rainy, it is necessary to get more daylighting access into the interior space for lighting as well as reducing the energy consumption on electricity lighting. Therefore, tall windows including skylight and side windows are applied in the Bullitt Center. What’s more, narrow floor plans are also designed for daylighting.
(2) External Blind for shading
The windows and the external blinds covering them are automatically controlled by sensors and timers to regulate the amount of light, heat, and air in the building. If temperatures get too hot, the windows open to circulate air through the building. The blinds may also be lowered or raised and tilted at various angles to minimize or maximize the building’s heat gain and eliminate glare.
Skylight of the Bullitt Center
Side windows of the Bullitt Center
Operable exterior blinds to control heat gains
Fresh Air Delivery
The theory of heat recovery ventilation
(1) operable windows for ventilation and cooling
In the Bullitt Center, every occupiable, interior space is required to have operable windows that provide access to fresh air and daylight. Furthermore, the windows are equipped with automatic window control mechanism in sync with local weather station.
(2) Demand-controlled heat recovery ventilation
Massive amounts of treated air can be lost through a building’s ventilation system. This means that the heating and cooling systems would have to work extra hard to keep the Bullitt Center thermally comfortable, which could jeopardize the goal of net zero energy use.
The concept of a heat recovery ventilator is quite simple; the tempered outgoing exhaust air gives off its warmth or ‘coolth’ to the incoming ventilation air. The transfer occurs within a honeycombed, rotating drum. The material of the honeycomb is very thin and very conductive, so the heat can be transferred efficiently. The purpose of the drum is to transfer as much heat as possible without contaminating the incoming air with exhaust air.
The air then passes through a hot or cold coil depending on the season, to further preheat or pre-cool the ventilation air. This coil is supplied by the ground source heat pump system. The system, developed by MEP engineering firm PAE, lives on the roof of the Bullitt Center under the array of solar panels.
The Transport System
The Bullitt Center not only relies on energy from the ground and sky, but also from its occupants. Set in a central, walkable neighborhood, the Bullitt Center is in a prime location to be accessed by bicycle (as well as foot or transit). Bullitt Center provides no onsite parking for single occupancy vehicles, instead housing 29 bikes. An adjacent workstation also provides a convenient space for repairs when needed.
The final inducement for cycling to work is the hot showers and changing rooms that live on every office level. Nobody wants to spend the day at work shivering, sweaty, or soaking, so there is an opportunity to freshen up before work after the days ride.
While far from high tech, these solutions offer simple ways to ease our reliance on cars. And with the advent of electric bicycles, and bike racks on public transportation, more and more people are able to use the bicycle for transportation and not just recreation.
