Advanced Environmental Concepts in Sydney, Australia, a division of Lincolne Scott, is Australia's only professional practice dedicated to the design of passive and integrated environmental systems. Che Wall, group director of both companies, made a presentation at USGBC's GreenBuild Conference last November about sustainable efforts in the Land Down Under, including some neat technologies in a project called Council House 2 or CH2. Su-Fern Tan, an environmental design consultant with AEC, was also involved with the project. Following is an interview with Ms. Tan on some of the innovative systems in the project.
CSE: The CH2 facility is driven by a lot of water-based systems. Why?
Tan: Several years of drought here have made Australians realize that water is a precious commodity. Therefore, water-saving technologies such as the sewer-mining plant have great potential for growth. Of course, the cost of water here in Australia, plus public sewerage levies, has made payback periods reasonable. This will be even more critical considering the Australian government's plans to increase the cost of water.
CSE: You mentioned sewer mining. What exactly does that involve?
Tan: A sewer-mining system, also known as multiple water re-use, harvests Grade-A quality water directly from the sewer through non-chemical and non-biological ++processes. The plant needs access to sewerage either via a connection to sewer mains or a sewerage tank. The reclaimed water first undergoes a micron pre-screening, then micro-filtration, and finally, reverse-osmosis.
In the process, 80% of the reclaimed water is extracted as Grade-A water, which meets the World Health Organization's Drinking Water Guidelines and U.S. EPA national primary and secondary Drinking Water Standards . The remainder of the original load is returned to a sewerage treatment facility via the sewer system. This is the key, as sewer mining significantly reduces the load on the public sewer system, which typically is comprised of 90% clean water.
CSE: In his GreenBuild presentation last November, Che noted CH2 was a demonstration project, and in his estimation, the greenest building in the world. For our more practical readers, that translates to a building filled with fairly exotic technologies that may never see widespread incorporation. That being said, what green systems in CH2 do you believe have the most potential for widespread adoption?
Tan: There are two systems that have immediate potential: the sewer-mining plant and the chilled-beam/ceiling cooling system. With the former, significant risk and financial analysis was part of the due diligence process. The owners of the CH2 project, Melbourne City Council, decided to invest in this technology. It had been in existence at the time—and still is—in Singapore at the Kranji NEWater Reclamation Plant where it supplements the city's water supply.
As far as chilled beams, they're already becoming popular and the industry elite has already started jumping. It seems everyone wants to have the next chilled-beam building. Also helping things are energy regulations, which are forcing engineers to look at lower-cost energy solutions.
CSE: Chilled beams are fairly rare here in the United States. How does this technology work and what led you to incorporate it in the project?
Tan: Chilled ceilings and beams use water, not air, to transport heat. The space is cooled through radiant and convective exchange where heat is exchanged between surfaces of differing temperatures and cool air descends freely from the ceilings and beams, instead of being blown into the spaces by fans. The air system exists solely to supply fresh air into the space.
Ceiling surfaces are normally in the range of 59%%MDASSML%%65°F, which provides a much more pleasant radiant cooling effect for people with minimal air movement—and also provides a cleaner and natural indoor climate for occupants.
As far as our motivations, chilled technology offers all the following benefits:
Significant energy savings
Smaller plant requirements
High indoor-air quality—no contaminant mixing
Space savings—no high-volume ductwork
Increased comfort—no drafts, even cooling and more pleasant cooling temperatures
Lower maintenance/higher life expectancy, due to the absence of moving parts
Elimination of risk of mold growth
The ability to harness free cooling in the Melbourne climate
Chilled ceiling panels are custom designed by AEC in collaboration with the architects to be an aesthetic feature, and so their function can be seen by visitors to the space.
CSE: You note the elimination of mold as a benefit of the system, but a negative I've heard associated with chilled beams is the concern about mold from condensation, and also the cost compared to other available green technologies. What's your experience been?
Tan: Actually, chilled-technology systems are far superior to a conventional overhead air-supply system because they practically eliminate the possibility of mold growth.
Air is introduced into the space solely to provide fresh air for occupants, not for cooling, which means that supply-air temperatures are higher in these types of systems. This also means that the relative humidity of the air is significantly lower, and this limits the potential of mold growth.
Also, the existence of chilled elements in the space requires the system to be designed to eliminate condensation from moisture in the space. This is done by controlling humidity, which again reduces the possibility of mold growth.
CSE: How do you govern these systems?
Tan: Control is via a computerized building automation system. This provides a fully integrated system for all aspects of the building, which goes further than just services to include mechanical services, electrical services, lighting, lifts, security and passive design elements such as windows and wind turbines.
As part of the control systems, each chilled ceiling/beam is self-regulating and responds to the area served by each element. Each is provided with a control valve that adjusts chilled-water flow depending on temperature and humidity.
The relative humidity in the space is closely controlled as a function of the air supply that responds to humidity sensors located throughout the space. Finally, air supply via floor grilles can also be individually controlled by occupants. The supply-air grilles in CH2 allow occupants to redirect or reduce supply air through simply twisting the grille.
CSE: For the record, underfloor air was also part of the HVAC system. As you just noted, it's more for bringing in fresh air and offering personal ventilation control than for heating or cooling. But back to the concept of chilled beams, wouldn't their location in the ceiling compromise the laminar flow of the displaced-air system? Just how do these two systems interact, and if it's a problem, how do you overcome this issue?
Tan: A true displacement system is where air is supplied into the space from the floor, gains heat from the space and rises to the ceiling exhaust without obstruction. So yes, the chilled ceiling elements do disrupt the flow of a true displacement system. However, what we have found is that with computational fluid dynamics analysis and laboratory testing, the two systems can run in parallel and still be quite effective. Fresh air essentially forms a layer close to the floor. When it gains heat from occupants or equipment, the air rises, mostly overcomes convective and radiant cooling forces from the ceiling, and is exhausted out effectively. In this particular case, we employed an undulating concrete ceiling line as the exhaust plenum. The plenum is kept at a slightly negative pressure, induced by north flues, which ensures that warm air completely exits the ceiling spaces.
CSE: On the subject of cooling, one of the neatest technologies of the building is the "shower towers," which was your alternative to a cooling tower using evaporative cooling. Can you please expound on this principle?
Tan: The shower towers (see figure) simply use the principle of evaporative cooling to bring down ambient air temperatures to a wet-bulb temperature minimum. As long as there can be a noticeable difference in a temperature drop, then the objective has been achieved. Although greater cooling effects are felt in drier climates, due to the differences in wet- and dry-bulb temperatures, their use is not limited to these types of climates.
AEC has pioneered the use of shower towers in Australia, and we have found that as long as there is a noticeable difference in temperature drop, the shower tower is successful. Turning a fan on in summer provides cooling purely through air movement. The shower tower provides air movement and lowers the temperature of the air. This is why even a small drop in temperature for example, 4°C makes a noticeable difference, especially coupled with air movement.
For the CH2 building, the shower towers rely on mains/tap water as their water source, as the approvals process for treated water was too convoluted. The water in the shower towers is pumped back up to the top of the towers to be "showered down" again, and so on, in a continuous cycle. The small amount of water that is lost from evaporative effects is topped up from mains water so we have a constant volume and constant flow cycle whilst the tower is in operation.
CSE: The shower towers were built onto the exterior as an architectural element. What was the architect's reaction? For that matter, how did the whole architectural-engineering process go? For example, a lot of concrete was employed for thermal mass, and the precast for the underfloor ductwork alone obviously took a lot of interaction with the rest of the building team.
Tan: We were fortunate to work with architects who were extremely open to new ideas and eager to incorporate innovation in environmental sustainability with innovation in architecture. This is why the design integrated architectural and engineering processes, and was successful even through many challenges and difficulties. We all know, and it has been well researched, that there is a directly proportional relationship between teamwork and success. However, this kind of teamwork needs to be enforced into an entire interdisciplinary design team to deliver best results.
CSE: At the GreenBuild conference presentation, it was noted that approximately 15% more was spent on the HVAC systems than a more typical building, but in the end these costs were offset. How did AEC accomplish this?
Tan: Although the actual cost of the chilled ceiling and beam solution was calculated to be 15% more than conventional systems, the capital cost of mechanical services was offset by a reduction in plant room space requirements, leading to a more efficient floor plate and an increase in leasable area due to a reduction.
CSE: A final question: The building is clad with lots of unusual elements that are part of the daylighting strategy. Can you please expound on the building's general lighting scheme, including dimming controls.
Tan: A low-energy artificial-lighting system was designed for CH2 consisting of low-level ambient lighting and individual task lighting. Automated dimming of artificial lighting is incorporated at the perimeters in response to daylight levels where each light fitting is fully addressable. Thus the level of lighting will reflect the level of activity in the space.
Natural light is redirected via light shelves on the north fa%%CBOTTMDT%%ade to encourage indirect lighting; perforated metal shading on the east fa%%CBOTTMDT%%ade; and recycled timber louvers on the west fa%%CBOTTMDT%%ade that automatically move with, and provide shading from the sun. The timber louvers are motorized to track the sun. Photovoltaic panels on the roof power the system.