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A team formation

The team Aqua Virentum is comprised of three architecture students with diverse backgrounds and experiences in environmental engineering and urban design. The fourth member of the team, a biology student, brings an understanding of natural science. The team is supervised by an architect and landscape architect with an interest in sustainable building and an emphasis on performative components of both built form and landscapes. Brainstorming

The team looked at the various ways that water exists in our lives, drinking, playing, irrigation, etc. We also looked at how water can be used in conjunction with built form and the potential for more integrated approaches to building forms and systems. Green roofs and roof catch systems were examined and revealed that the water retained on site is used for very limited purposes. Water is primarily used for irrigation of plants and vegetation on-site and toilet flushing. As a team, we recognized that this seemed rather limited and there is potential.

To conform to the biomimetic nature of this competition, we reviewed some natural processes by plants and animal species on capturing and retaining water. Locally, conifers are able to survive the harsh climates of winter due to their unique “leaves� that reduce the amount of moisture lost when there is insufficient water in the soil. In addition, we noticed that certain plant species can strive despite being isolated from soils entirely. This led us to discover the brilliant mechanisms that epiphytes have developed that allow them to exist great heights above the soil. Some have cup-like trichomes that allow them to capture rain or water-run off from the host it clings from. Other species like mosses have tiny hair-like cilia that absorb water directly from the air.

This motivated us to explore the potential of systems that attach to the walls of buildings and capture rainwater to be re-used on site. Existing uses for harvested rainwater are rather limited. When we reviewed how buildings are cooled in deserts, we realized that passive evaporative cooling can be employed anywhere that experiences active air. The office building in an urban core became the default prototype to investigate the feasibility of our system. As offices tend to have towering walls that experience rain, we felt there was potential to harvest the rainwater that would run vertically down the side of it by looking at how the epiphyte organisms capture water running down the sides of its host.

In addition, the high energy consumption of office buildings in respects to other uses made this project suitable to being deployed in urban centres that are heavily populated by office towers. These office towers can use as much as 23% of their annual energy consumption on strictly cooling. By offering an alternative, we can directly address these demands.

Finally, the Aqua Virentum project hangs as a brise-soleil system that offers shade for the users of the interior space. It also offers some form of protection against the heat island effect that is of growing concerns in urban centres. As the system is designed as retro-fit, it can be easily deployed and actively assist in countering excessive rainwater run-off, high energy consumption for cooling purposes and also the heat island effects.

Local Water Issue: Water Cycle Interference Large urban centres contain sophisticated networks of roads and structures. While these are vital to the livelihood of a city, they also introduce a problem to the pre-existing natural environment: water cycle interference.

Hard surfaces hinder precipitation from reaching soil where it is absorbed by vegetation and eventually evaporated back into the atmosphere.

This disruption is a two-fold problem as rainwater that does not immediately re-enter the water cycle is likely to carry pollutants before it enters our rivers, lakes or stormwater systems.

Green roof systems currently address this issue, but through the use of synthetic epiphytes, rainwater can also be captures from vertical faces of buildings.

By harvesting rainwater, the Aqua Virentum project aims to restore a greater harmony to the water cycle, while also reducing both environmental impacts to the watershed and municipal stormwater system demands.

Bromeliad (Aechmea bromeliad sp.) A. bromeliad is an epiphyte common to the humid rainforests of South America. The vascular bromeliad intake water and nutrients by means of trichomes, cilia-like structures that proliferate throughout the organism’s leaves. Under magnification, trichome tips resemble a concave disc, allowing the organism to passively regulate water transport.

central disc cells



dome cells

foot cells



LEFT:  Passive absorption of water by the use of trichomes in A. bromeliad. 1. when pointing upwards, the wings on the trichome don’t allow the passage of water below;

2. water fills the tip in wet conditions and pushes the wings downwards;

3. while flush against the trichome stalk, the wings creates a pathway for water intake beneath the cap.

Liverwort Moss (Chiloscyphus polyanthos sp.) C. polyanthos, commonly called liverwort moss, is a freshwater moss widely found throughout the wetlands of Northern Europe and many areas of North America. As the organism is a non-vascular byrophyte, it lacks an inner transport system (xylemic or phloemic) to allow for unsupported structural growth. Rather, the organism adheres to existing surfaces by means of rhizoids, unicellular cilia that both draw water and secrete nutrient digestive enzymes. RIGHT:  Rhizoids on the underleaf of C. polyanthos intake water by creating an external capillary system on the surface of and between the mass of filaments, drawing water to the cell wall of the leaf for absorption.


atmospheric water

Design strategy Learning from the evolution of epiphytes and their nature to hang on the hosts, we explored a design that incorporates a panel system that is attached on the walls of tall office buildings. fog collection

organisms “attached� to hosts

rainwater collection

Design: The Epi-Panel steel mesh panels

The resulting design is the Epi-Panel. Like the epiphyte, this system attaches itself to the outside of existing buildings with minimal intervention on the host structure. Using a prefabricated panel system, the mechanisms for fog and rain capture learned from the studied organisms has been adapted to an urban setting.

Liverwort Moss: An array of polygonized steel meshes mimics the cilia mechanism by providing a large, dense surface area for water condension. By using a mesh, the panel still allows for light penetration.

Bromeliad: A line of drip catchers allow surface runoff to be caught from the walls of the building as well as the accumulated water on the steel meshes above. These catchment basins drain to a cistern located inside the building. Like the trichome devices, the collected water is only used for evaporative cooling when there is a sufficient amount to sustain prolonged use for maximum efficiency.

aluminum drip catchers

A Symbiotic Solution The system as a whole attaches to the curtain walls on a typical office tower using the building’s existing structure. Existing mullion caps are removed and sent to be recycled. They are then replaced with custom caps, designed to accomodate the Epi-Panels, allowing the system to fasten directly to the existing vertical mullions. Through this, the application of the Epi-Panel system to a building stays unintrusive, and waste is kept to a minimum.

1. custon mullion cap w/ extended drip 2. steel mesh fog fence

6. B


A 4.


3. custom mullion cap


4. 1/2� steel structural outrigger


2. steel mesh fog fence

9. 1.

10. aluminum outrigger fastens to existing vertical mullion

5. steel mesh fog fence

The epi-panel system is a green retrofit for curtain wall systems to harvest water from the sides of buildings through both rain and fog collection.


6. aluminum drip catcher 6. aluminum drip catcher 7. horizontal steel panel mounting rod


9. penetration of building exterior done at insulatied spandrel panel

The evaporative cooling unit is intended to supplement existing HVAC systems in buildings to offset energy costs.


8. 1/2� copper water intake pipe

The collected water is stored in a cistern which is primarily used to supply water to an evaporative cooling unit when water levels are high enough to maintain sustained use. Excess water used for greywater purposes.



Assembly Details

Exploded Axo




when there is no drip catcher immediately below, the panel drips down the the next available catchment basin

fine steel mesh panels encourage water condensation


the majority of the rain collected will be from the window surface

an extended drip flashing on the mullion cap allows surface runoff to drip to the catchment basins

condensed water drips down and is collected in aluminum drip catcher below

numerous catchment basins share the same inlet point to minimize building envelope penetration

The cooled air from the evaporative cooling unit is fed into the existing HVAC system. By cooling the air before it is fed into the system, the existing HVAC requires less energy to maintain a comfortable interior temperature.

When a sufficient amount of water has been collected, the water will be fed into an evaporative cooling unit.

Water collected from aluminum catch basins is piped to an internal cistern. Though primarily used for evaporative cooling, the water is also used for greywater purposes.

Existing HVAC Integration

Completing the Stormwater System

Traditionally, the strategy for water when dealing with building envelopes was to shed water away from the building. But with water pollution and high peak flow rates become a major urban problem, local site water retention strategies have seen signficant developemtn. However, these strategies have mainly focused on horiztonal surfaces, leaving the large vertical surface largely untapped.

The Epi-Panel bridges this gap and completes the site stormwater retention system. This type of system is particularly necessary in urban settings, where ground level stormwater systems aren’t an option. With the large volume of water that can’t be collected by the limited surface area of a green roof, it becomes vital that advance our ability to control water throughout the rest of the building.

Sunshade Benefits

The Epi-Panel meshes provide a translucent surface that block out 80% of incoming light. With 26% coverage of the available vision glass (away from eye level so as not to obstruct views), the Epi-PAnel system provides a 21% decrease in solar heat gain.

Maxmize Efficiency To maximize the efficiency of the Epi-Panel system, excess modules have been removed. A study of wind driven rain has shown that most of the wind driven rain accumulates towards the upper portion of the facade with concentrations towards the edges, similar in form to an inverted parabola. Reducing the number of panels used saves on material cost while still maintaining the system’s effectiveness.


Surface Area Coverage




Surface Area Coverage



TORONTO GETS     OF   A YEAR. 622 mm ( Avg. rainfall per day in Toronto ) ( Avg. number of rain days per year ) = Total rainfall per year


388 580 L OF   .     RETAINS       

3 629 338 L

     RETAINS             .

( Total rainfall per year ) ( Surface area in contact with rainfall at 55 degrees ) = Rainfall retention



$21 382 A YEAR     SAVES      

$18 146 A YEAR     SAVES      



$199 710

    SAVES         .

( Rainfall retention ) ( Cost spent on evaporative cooling per liter ) = Savings on evaporative cooling

$169 487

    SAVES         .

( Rainfall retention ) ( Cost of water utility per liter ) = Savings on greywater usage




( Surface area of 50-storey tower ) ( Savings on stormwater/sewage diversion ) = Municipality savings


$8 232


     THROUGH SUN SHADING. $29 204 ( Surface area of 50-storey tower ) ( Cost of energy rate per metre sq. ) = Energy bill savings

Be resource efficient. The Epi-Panel system has been thoroughly designed with resource efficiency in mind. Both through its function and its construction, the ability to maximize the potential value of any resource has not gone unexplored. From the earliest brainstorming stages, our team has been looking for ways to capture and utilize water in the most effective way possible. The Epi-Panel strategy represents the Aqua Virentum team’s multipurpose response to the various energy demands of large buildings (cooling, flushing, irrigation, shade, etc.), and decided to utilize water as a response to all of them. It’s design is comprised of a lightweight steel, aluminum and copper assembly that attaches onto the existing structure of curtain wall systems. This was done not only to save material in fabrication, but also to avoid wasting any existing components when retrofiting existing structures. Further, these materials are all 100% recyclable, so at the end of the product’s lifecycle, all the materials can be easily recovered. Finally, the system has been optimized based on wind driven rain data to function in its most materially efficient configuration.

Use life-friendly chemistry. The Epi-Panel is an assembly of steel, aluminum and copper. These are all very evironmentally friendly materials and are among the most recycled industrial metals. As such, the environmental impact (and more specifically carbon footprint) that the Epi-Panel would have would be from fabrication and transportation costs. However, due to the simple nature of the components and the lightweight construction of the system, these impacts are kept to a minimum. Because the system occupies a very high profile position on large buildings, buyers may want to customize the appearance of the panels. In this scenario, low VOC paint will be used so as to keep any harmful sideeffects to a minimum.

Be locally attuned and responsive. With regards to water, Toronto can be characterized as a typical North American modernist city. Despite it’s relatively young age as a city, it has a vast infrastructure system that the government struggles to maintain. The inadequacy of stormwater management was seen in 2005, when a flood overwhelmed the city’s infrastructure and even washed away a major road. The source of these water related problems can be traced to the high peak flow rate of runoff water caused by the increasingly impervious urban landscape. For Toronto, this trend is an important one as the city led North America in number of high rises built in 2012. Because of Toronto’s vulnerability to water and it’s rapidly growing stock of tall buildings, our team knew immediately that this was an issue we needed to address. Through the Epi-Panel system, our design responds to the issue of an increase in impervious surfaces in an urban setting through a mechanical means of sequestering water. However, as the local building stock becomes increasingly populated by high rises, the need to address the large cooling loads rises. The Epi-Panel resolves this energy constraint both through evaporative cooling using water collected from the side of the building, and also through a reduction in solar heat gain by acting as a brise-soleil.

Design limitations. The prototype design is based on office towers being capable of retrofitting their ventilation systems to adapt to our design. The biggest limitation of the current design is that it cannot accomodate every structural system as a one-size-fits-all to retrofit older office buildings. On a similar note, the ability to retrofit existing buildings relies on certain interior configurations that are typical in an office building. For example an open plenum above a dropped ceiling allows piping to be installed without running the system through habitable interior space and without structural intervention. With regards to the large number of residential buildings that could potentially benefit from the Epi-Panel system, the application would need to be at a new construction stage rather than a retrofit scenario. Finally, accurate testing on the volume of water a mesh can collect through condensation remains to be explored. With more empircal data, the Epi-Panel design could be further refined.

Citations. Blocken, B., Derome, D., and Carmeliet, J. “Rainwater runoff from building facades: A review.” Building and Environment. 60 (2013) 339-361 Benzing, David H., Karen Henderson, Bruce Kessel, and JoAnne Sulak. “The Absorptive   Capacities of Bromeliad Trichomes.” American Journal of Botany 63.7 (1976): 1009. Print. Glime, Janice M. 2007. Bryophyte Ecology. Volume 1. Physiological Ecology. Ebook   sponsored by Michigan Technological University and the International Association of  Bryologists. Krishna, J. H. The Texas Manual on Rainwater Harvesting. Austin: Texas Water   Development Board, 2005. Print.

Biomimicry Design Challenge FINALIST  

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