The Terry Thomas is a new four-story office building in the South Lake Union neighborhood of Seattle. Completed in 2008, it was designed to provide a healthy and creative work environment that would illustrate the possibilities of sustainable design. This energy-efficient structure was designed to achieve energy savings of about 40%.
With the training and cooperation of building occupants, actual energy savings have exceeded 55%. This demonstrates that green building is for everyone, not only architects and engineers. Each and every person who uses a building can join the green building team by becoming acquainted with the most efficient way to use the building to stay comfortable and productive.
It is believed to be the first multi-story office building designed and built in Seattle without a mechanical air conditioning system for at least 50 years. Because of the region’s temperate climate, a cooling system based only on natural ventilation keeps the interior within comfort limits except one or two days a year, when employees are encouraged to wear shorts.
Eliminating a traditional HVAC system in favor of a passive cooling system brought cost savings in both construction and operation. The central courtyard plan allows optimal distribution of natural light and ventilation while reducing energy dependence. The building’s courtyard works together with vents, controls and window openings to create a stack effect, drawing warm air out and up through the courtyard.
The stack effect is the natural flow of air resulting from warm air rising, creating an increase in air pressure at the top of a
building and a negative pressure at the bottom. If the warm air is allowed to escape at the top, then fresh, cooler air will be drawn into the bottom. This effect can be used to advantage for natural ventilation and cooling when the openings at top and bottom are properly regulated.
Besides saving the energy required to power mechanical cooling equipment, the passive, natural ventilation system does not require electric fans to distribute air. Heating is accomplished with standard hot water radiators. Because no air ducts are required, the height of each floor was reduced, making the building more compact. With less exterior surface, winter heat loss and summer heat gain are both reduced. Also, fewer materials were required to make up the building.
Each side of the building was designed to respond uniquely to wind direction, solar angle, and views. The east and west elevations feature smaller windows with protected sunshades to reduce solar heat gain. Exterior shades controlled by a sensor on the roof measure the light level and sun angle to open, close and adjust as necessary, reducing glare and direct solar radiation on the south- and west-facing courtyard sides.
Operable windows are located to encourage cross-ventilation and capture prevailing breezes. Louvers automatically open and close open to maintain temperature and air freshness, and to cool the building at night.
The building is designed carefully to reduce electricity use by maximizing day lighting. The openness of the floor plan enables daylight to penetrate to the interior. Light-colored finishes are used throughout, as are reflective ceilings. Electric lighting is controlled by automatic photoelectric daylight sensors, occupancy sensors and dimming switches.
The proportions of energy used for various functions in a typical office building are shown in Figure 1.
Figure 1 Figure 2
The major energy-saving strategy of the Terry Thomas building is to dispense with mechanical cooling and ventilation (Figure 2).
Energy use for heating is reduced by passive building features as well as efficient systems, and electricity for lighting is reduced by effective daylight harvesting (Figure 3).
Figure 3 Figure 4
And the total savings projected by the design team were approximately 40% (Figure 4).
The outstanding energy savings realized by the Terry Thomas building serve as an excellent example of the effectiveness of demand reduction as a basic strategy. Note that this building does not yet rely upon any renewable on-site power generation!
Courtesy Weber Thompson, Seattle
Pie Charts: US Department of Energy, 2007