Austin City Hall

Introduction

Completed in 2004, Austin's City Hall is one of the most unique Green Buildings in the world. Designed by Antoine Predock to reflect its natural surroundings, the four-storey, 9,300 m2 (100,000 ft.2) structure incorporates local limestone, a cascading waterfall, and non-symmetrical shapes, all of which reflect the waterways and canyons of Austin's surroundings. The top two floors, roof, and 'stinger', projecting 15 m (50 feet) out over a neighboring street, are clad in copper, playing the role of the sun in this homage to the landscape. The unique and at times controversial design is anchored by a number of very practical and meaningful features designed to meet the goal of transparent government and providing a meeting space for the continual benefit of the city of Austin, TX.

What Defines a Sustainable Building?

Overview - The building is located in the reemerging Warehouse District and represents a centrepiece of what is expected to be, through proactive planning, a vibrant part of the city. It is set slightly askew from the street to provide unique outdoor spaces around the building including a large open plaza which has been developed with concerts in mind, including a limestone stage and amphitheatre seating shaded by photovoltaic cells. These have been integrated into the design to facilitate and compliment the city's casual style and love of live music. The designers took advantage of the building's construction to develop a space which could serve numerous purposes in the city's life and culture beyond simply housing its administration. They worked with stakeholders, such as the local media, to ensure that it met their needs as well.

This consideration is reflected in many details throughout the building. First when individuals walk into the building, they find themselves standing in a canyon like space that reaches up to the roof disturbed only by catwalks joining its different sides. The council chambers have theatre-style seating for 156 and screens both inside the chambers and in the lobby to allow the public to monitor the proceedings.

What Makes it Green - the Building's Features

When the City Hall project was initiated, all of those involved were committed to achieving a LEED rating, and it is clear that numerous features have been incorporated to facilitate this. According to Deb Ebersole, of Cotera+Reed Architects, this was done because "it's the right thing to do, Austin has always been green and this is a good way to compare ourselves to others."1 Ebersole commented on how this was complicated by trying to bring together the construction realities with the ideas behind the design and accomplishing them within the context of meeting the LEED standards. Their success is apparent with the U.S. Green Building Council awarding the building a LEED Gold certification. To achieve this they were particularly successful in three areas: the reuse of materials, energy use, and a number of features which make the building more functional for users. Copper's role in each of these areas is reviewed in greater detail in the next section.

Material Reuse

This project was very successful in reusing material from diverting construction waste, to reusing the air-conditioning condensation, to using materials with high recycled content. More than 50% of the construction waste was diverted from landfills with appropriate pieces of ceramic tiles, wood and concrete going to local artists and schools.1 Air-conditioning is a practical necessity in Austin but the designers have reused the condensate generated to feed the waterfall which streams into the south plaza. Finally, many of the materials used throughout the project including copper, steel, drywall and concrete masonry had high levels of recycled content.

Energy Use

Design features throughout the building minimize its energy use especially in relation to keeping the building cool. To shade the building, the designers planted large mature trees rather than using smaller ones typically seen at new constructions. They chose to use an underground parking garage which has reduced the building's footprint and the amount of reflected heat which could have been generated by a street level lot. Further, the building is part of Austin Energy's Downtown District cooling system which uses a unique system to generate ice overnight, when electricity demands are lower, and it is cheaper. The ice is then used to generate chilled water which is used to cool the building improving its energy efficiency. For the energy the building does need, the city has committed to purchasing 50% of it from renewable sources through Austin Energy's Green Choice program. This program relies primarily on wind-generated power but also water and methane gas generation.2

Building Features

Despite its striking design, it is clear that the designers did not lose sight of its users. From the inclusion of showers and change rooms to the use of low to no volatile organic compounds, this becomes very clear. By providing a place to clean up and change, the designers have removed one of the largest obstacles to alternative forms of commuting, and by using paints, carpets and adhesives with low to no VOCs, the indoor air quality is improved dramatically. This latter point is a distinguishing feature of Green Buildings which are often described as feeling exceptionally clean. Finally, the solar panels over the main stairs act as a design feature, a power source, and a source of shade for people watching events in the plaza, an important feature given the city's love of live music.

What Defines a Sustainable Building?

Copper played an integral part in almost every aspect in this building including its striking design features and advanced technology. In fact over 5,575 m2 (60,000 ft.2), or more than a football field's worth, of copper was used primarily to 'wrap' the top half of the building including of course its unique 'stinger'. The 300 mm (12-in) copper clad panels and standing seam copper roof were treated with a light oil coating to slow their patination, and due to the low amount of sulphur in Austin's air it is expected that in about 30 years, it will turn a soft grey with hints of blue and green. Not only was the colouring important, given the design objective of an homage to the local environment, but the fact that copper can be manipulated to fit into unique spaces was critical because the building has few 90-degree angles. The copper features continue into the building. In the lobby a bronze ceiling reflects the sun coming in from the skylight into the space below.3 In the council chamber 16 "copper clouds" dominate the ceiling acting as both design features and corrugated acoustical panels designed to improve the room's sound quality.

Finally, the fact that this football field's worth of copper had 82% recycled content helped contribute to being awarded the LEED point for recycled materials. Further, the only energy needed to make cladding from recycled copper is for the heatto melt it, or 15% of the total energy consumed if it were mined, milled, smelted and refined from ore. This translates intobig energy savings, as over 80% of copper used to make architectural sheet products comes from recycled copper.Finally from creation to use, copper can last two or three times longer than other exterior materials, and thus equate to less material consumed over the building's life span.4

The city took advantage of the opportunity of building a new City Hall to update all of the building's technical features. In total they used 230,000 m (750,000 feet) of copper cabling in various applications to facilitate the transparency of government, advances in technology, and the desire to make the building useful to a variety of users. Copper cable is the most efficient and reliable electrical conductor, is easy to install, repair, and is more durable and cheaper over its life cycle than aluminum. Further, at the end of use all of this copper cable can be recycled into other copper and brass products, like tube for air-conditioning equipment, cladding and hardware which have an average recycled content of between 66 and 95 percent.5

The designers worked closely with the local media and the city's own news channel to make the building 'media friendly'. This included installing lighting as well as audio and video plug-ins throughout to allow media to broadcast live from almost anywhere. The city's media equipment had not been updated in 18 years and there was a need to bring it up-to-date. There was an obvious effort to make technological decisions not only based on the needs of today but where possible also on those of tomorrow. To support the city's love of live music, the sound systems were installed to maximize the usability of the space.

Conclusion

The adventurous designer Antoine Predock did not hold anything back on Austin's City Hall despite the clear goal of achieving LEED certification. The result is an exceptionally unique green building with many features which make it functional, aesthetically pleasing and environmentally beneficial. Copper has played a fundamental role in achieving these goals, both directly contributing to LEED certification and indirectly via its use in "green"/environmentally beneficial technologies for effective use of energy and materials throughout the life of the building. This includes the 6,000 m2 (66,000 ft.2) of copper cladding which wraps upper two floors of the building representing the sun, to the copper acoustic panels in the chamber supporting the promotion of live music, to the near million linear feet (320,000 m) of cabling used to support the technological features of the building. This building shows how environmental and aesthetic qualities can work in harmony and the way forward for the future of cutting edge design.

  1. City of Austin - Austin City Hall and Public Plaza.
  2. Austin Energy - Green Choice Program.
  3. Predock Architecture "Austin City Hall and Public Plaza".
  4. Copper Development Association "Copper - The 'Green' Metal" [Not yet released].
  5. CopperInfo "A Comparison of Copper vs. Aluminum Electrical Wire & Cable".