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10-Story Building in Melbourne Uses Five 13-Meter Water Towers to Cool Air by Evaporation by Up to 13 °C and Reduce the Load on the Air Conditioning System. This Technique is Known as Shower Towers.
In downtown Melbourne, a 10-story building spanning 12,500 m² employs a system that appears to turn rain into air conditioning equipment. Council House 2, known as CH2, features five vertical textile towers measuring 13 meters in length and 1.4 meters in diameter. They draw external air from over 17 meters high and circulate water down their interiors. The evaporation process extracts heat from the air before it reaches the commercial spaces on the ground floor. Tests of the system recorded temperature drops between 4 °C and 13 °C.
The cooled water is not wasted after falling. It enters the building’s thermal circuit and helps pre-cool water from the refrigerated ceiling panels, increasing the efficiency of thermal storage with phase change materials by approximately 10% to 20%.
The shower towers do not solely replace the building’s entire air conditioning; instead, they integrate into a much larger architectural framework that combines thermal mass, ventilation, refrigerated ceilings, shading, and water recycling to significantly reduce reliance on conventional systems.
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Five Giant Tubes Descend the South Façade of the Building
The most visible element of the system is located on the south façade of CH2. Here, five shower towers, literally rain towers, have been installed.
Each tube is approximately 1.4 meters in diameter and 13 meters long. The material is lightweight, but the function is primarily thermal: to create a vertical path in which water and air can interact during the descent.
The air is captured from at least 17 meters above street level. After entering from the top, it follows the flow of water down and loses heat through evaporation. The movement of the water itself helps to pull air through the system.
The “Rain” Inside the Tubes Removes Heat from the Air
The mechanism does not rely on a compressor functioning like that of a residential air conditioning unit.
As some of the water evaporates, it must absorb energy to transition from liquid to gas. This energy is drawn from the surrounding environment, causing the air temperature to decrease.
It is the same physical principle that explains why the evaporation of sweat helps the human body cool down. However, in CH2, this process has been transformed into a multi-meter high infrastructure integrated into the façade of a commercial building.
The more suitable the temperature and humidity conditions, the greater the effect of evaporative cooling can be.
Prototype Reduced Air Temperature by Up to About 13 °C
Before installing the permanent system, the team conducted tests with a scaled-down version of the tower during the Melbourne Sustainable Living Festival in 2004.
The prototype was 2.5 meters tall and 400 millimeters in diameter. Water was pumped to the top and released through an internal shower. Engineers simultaneously measured the temperature of the incoming air and the temperature recorded at the outlet.
The technical document from the City of Melbourne summarizes the tests indicating temperature reductions of 4 °C to 13 °C. The original table includes even more extreme situations. In one measurement, the air entered at 40.9 °C and exited at 26.8 °C, a difference of 14.1 °C. However, performance varied mainly according to atmospheric conditions and relative humidity.
The system works best precisely when the air favors evaporation
The measurements show why there is no fixed temperature reduction. In a situation with a relative humidity of 66%, the prototype received air at 22.1 °C and delivered 17.6 °C, a drop of 4.5 °C. In another test, with a humidity of 35%, the reduction exceeded 14 °C.
Architectuul
This happens because evaporative cooling depends on the air’s ability to hold more water vapor. In less humid conditions, there is greater potential for evaporation and, consequently, for heat removal.
Therefore, the towers should be understood as part of an architecture adapted to Melbourne’s conditions, and not as a machine capable of producing the same temperature regardless of the weather.
The cooled air goes directly to the ground floor spaces
After descending through the towers, the cold air has an immediate use. According to the technical document of the project, it is directed to the commercial spaces on the ground floor, reducing the load required to cool them and meeting part of the fresh air intake needs during operating hours.
The shower towers do not function as the sole air conditioning unit responsible for all ten floors.
The building combines various technologies. The shower towers provide cooled air to specific areas and are part of the hydraulic circuit that assists another central component of the air conditioning system.
Water falling through the shower tower also exits cooler
While the air loses temperature, the water itself also undergoes cooling. The technical material of the project describes the final system working with water that can reach approximately 12 °C after passing through the tower. This water is not simply discarded into the street or sent directly to the sewer.
It is incorporated into the building’s thermal system and used to pre-cool the water returning from the chilled panels installed in the ceilings.
The idea is to take advantage of the same process twice: first to generate cooler air at the bottom of the towers and then to reduce the temperature of another water circuit.
Cold water assists a hidden “thermal battery” in the building
CH2 also utilizes phase change materials, known by the acronym PCM. Instead of storing electricity like a conventional battery, these materials store thermal energy.
By changing physical states at a specific temperature, they can absorb or release large amounts of heat.
In CH2, pre-cooled water from the shower towers supports the circuit connected to this system. The project estimated that this pre-cooling could enhance the effectiveness of the phase change materials by approximately 10% to 20%.
The result is an architecture where the water that appears as rain on the facade participates in a much larger mechanism of cold storage and transfer.
Concrete ceilings also work to remove heat from offices
The shower towers are just one piece of a deliberately integrated strategy. The offices feature ceilings and cooling panels that absorb heat generated by people, computers, and other equipment. The concrete itself contributes to thermal stabilization due to its mass.
City of Melbourne’s materials describe wavy, pre-cast concrete panels that are 180 millimeters thick, utilized as thermal mass capable of absorbing heat during the day and reducing cooling demand in the summer.
Instead of relying solely on large volumes of cold air blown into the spaces, part of the heat is removed by surfaces and water circuits.
At night, the building opens pathways to expel accumulated heat
Another strategy is the so-called night purge. When external conditions allow, the building utilizes the cooler night air to remove heat accumulated during the day. Windows and ventilation pathways help expel warm air.
DesignInc, responsible for the architectural project in collaboration with City of Melbourne, highlights that CH2 employs controlled opening windows, extraction ducts, and large turbines atop the building as part of this mechanism.
This reduces the amount of heat that remains stored in the building when a new workday begins.
Even the facade changes to prevent the Sun from overheating the interior
Reducing consumption starts before producing any cooling. On the west facade, CH2 features large movable elements made of recycled wood that protect the building from direct solar radiation. The system adjusts its position according to light incidence.
In practice, this strategy first prevents some heat from entering the building, decreasing what will need to be removed later by climate control systems.
The architecture also optimizes natural lighting and uses ventilation ducts, vegetation, and concrete as active components of the building’s environmental behavior.
CH2 was built as a low-energy buildings laboratory
The Council House 2 was completed in 2006, in downtown Melbourne, as a pilot project for the city’s emission reduction strategy.
DesignInc reports an area of approximately 135,000 square feet, construction costs of around 51 million Australian dollars (about US$34 million), and a 6 Star Green Star rating, the first awarded to a new commercial building in Australia.
The building was designed not only to house public servants but also to showcase technologies that could later be studied and applied in other projects.
Energy consumption dropped far beyond the effect of the five towers
DesignInc states that the set of technologies in CH2 reduces energy consumption by about 80% and water usage by 75% compared to benchmarks used in the project.
These reductions cannot be attributed solely to the shower towers. The performance results from the integration of shading, ventilation, thermal mass, chilled ceilings, energy generation, water management, efficient lighting, and other technologies.
CH2 was conceived as a system in which different components reduce small portions of demand, creating a much larger savings collectively.
The “artificial rain” shows another way to cool buildings
Twenty years after the completion of CH2, its five towers continue to attract attention because they make visible a process that typically remains hidden within machinery rooms.
Instead of simply turning on ever-larger compressors to combat heat after it enters, the building attempts to avoid thermal gain, store cold, exploit the differences between day and night, and use natural processes whenever possible.
In the 13-meter towers, this means pulling air from over 17 meters above the street, letting it rush down along with a rain of water, and removing heat through evaporation before it reaches the occupied spaces.
Tests conducted during development showed summarized reductions between 4 °C and 13 °C. The cooled water continues to work afterward, pre-cooling another circuit and aiding the building’s thermal storage.
Therefore, the engineering of CH2 did not completely eliminate mechanical systems. Instead, it did something different: it compelled water, concrete, wind, shade, evaporation, and even Melbourne’s night to take on part of the work that would normally be almost entirely assigned to the air conditioning.
