rainwater collecting system

for sustainable design


Sustainable Architecture Research Paper

Fall 2016, Regenerative Architecture

Professor Michael Garrison, the University of Texas at Austin

Collaboration with Isabel Albert

Solar Decathlon 2011 by University of Maryland

Solar Decathlon 2011 by University of Maryland



This paper presents a rainwater collecting system which is usually used to recycle storm water. Water is essential and restricted resource but it has been polluted by humans. Rainwater can be recycled for use in buildings, which significantly reduces water usage. From the viewpoint of design, the systems have good effects on designing elements of building. This is due to the rainwater collecting system being significantly related to roof design and also it can be separate elements for architecture. Positive effects and case studies that are integrated into the house are discussed and design aspects of this system are examined.

Keywords: rainwater collecting system, design possibility, roof design, sustainable design, recycling water



Water is the only commodity on Earth that cannot be replaced by an economic substitute. Water is a fundamental element for all life. Seventy-five percent of the Earth’s surface is covered in water, yet only 2.5 percent of it is suitable for human consumption. Of these, 68.9 percent is in the form of ice and permanent snow cover in natural environments.

A global water crisis is becoming more apparent due to the growing global population using fresh water resources. Dr. Peter Gleick, president of the Pacific Institute, has coined “peak water” as an explanation of the world’s water crisis. Overuse of water, climate change, and increased pollution by economic development may cause water shortages.

In Texas, there are water management strategies including conservation, new reservoirs, groundwater wells, water reuse, seawater and groundwater, and desalination plants. In the 2017 State Water Plan, approximately 5,500 water management strategies will help increase the water supply. Rainwater collecting systems can also reduce the amount of municipal outdoor water.

definition of rainwater collecting system

A rainwater harvesting system is an integrated group of elements that work together to provide collected rainwater ready for utilization. It is important to understand these fundamental elements, their functions, and the various components that comprise each of them. With this understanding comes an awareness of the interdependence necessary to integrate the elements into a successful system.

history of centralized water systems

Water is in constant motion in the hydrologic cycle. Populations have always grown where there is adequate water. In addition to gathering water from surface sources and wells, the use of cisterns has been documented in many cultures. Large cisterns and canals carved in rock for transporting roof-collected rainwater are found in Petra, Italy, dating from roman times.

Over the decades, the focus has been primarily on expanding the infrastructure to accommodate growth at the expense of maintaining the aging original infrastructure. The impacts of delayed maintenance, budget cuts, and disinvestment in aging infrastructure have become a twenty-first century political, economic and social crisis. Countries that lack functioning centralized water distribution systems continue to look to the developed world as a source for inspiration and technical knowledge for the future.

importance and benefits of rainwater collecting system

Rainwater harvesting systems have traditionally been implemented to meet potable water conservation goals. However, rainwater harvesting systems can be designed to meet many secondary objectives as well and thus, increase their overall benefits. These include:

      Managing storm water runoff and achieving sustainable building goals.

      Harvested rainwater is an alternative source of water that can be used to reduce the consumption of potable water.

      Rainwater can be used for many non-potable demands that are currently met with potable water such as irrigation, toilet flushing, cooling tower makeup, and washing clothes. With additional treatment, this water can also be used to meet potable water demands such as drinking, cooking, hand-washing, and bathing. However, these uses will probably represent a relatively small portion of the demand for most commercial projects.

      Supplementing potable water with harvested rainwater contributes to local, regional, and/or national initiatives to decrease potable water consumption and increase the resilience of fragile water resources.

      On a smaller scale, rainwater-harvesting systems can reduce the amount of money property owners spend on potable water. Additionally, these systems provide water with a lower mineral content than potable water, which may increase the longevity of building equipment.

      Many storm water regulations are pointing to rainwater harvesting as a viable storm water management practice, thus allowing property owners to receive credit for their implementation.

      In addition to meeting water conservation and storm water management goals, rainwater harvesting can also fulfill green building and sustainability initiatives. The incorporation of a rainwater harvesting system can create a sustainable, regenerative water infrastructure within a building.

None of these benefits are exclusive to one another and all are approaches that may motivate a property owner to include a rainwater harvesting system into the project. It is critical to clearly describe and detail the reasons for rainwater harvesting at the initial design stages in order to select an appropriate design and successfully integrate the system and building.

case studies of rainwater collecting system

Texas State is one of the few states in the United States that has tried to make significant plans and laws related to rainwater collecting systems. For instance, it allows for a state sales tax exemption on rainwater harvesting equipment. Furthermore, the plans have also encouraged the designing of new state buildings with rainwater harvesting system technology essentially and helped financial loans for developments using rainwater politically.


Potsdamer platz project, Berlin

From the viewpoint of an urban design, the Potsdamer platz project, in Berlin, Germany, has been evaluated as successful integrated urban rainwater systems and also famous for its aesthetics and public approaches. Atelier Dreiseitl, who designed this project, made streets for people to access water easily and created man-made natural environments using storm water from the buildings. With this water management systems, the plaza could be useful public space with new approaches while also providing a living space for biotope.

Potsdamer Platz, Berlin

Potsdamer Platz, Berlin


NexusHaus by the University of Texas at Austin, Solar decathlon 2015

The University of Texas at Austin solar decathlon NexusHaus represents another good example of water collecting systems in which rainwater similarly becomes a sustainable resource for the everyday use. It focuses on water conservation, treatment, and reuse.

The majority of the rainwater captured is used for potable water needs but the projects also relies on the city water line for backup during long dry periods. Because the water treatment system it being done in the same place where the water is collected it avoids a lot of water loss compared to the traditional municipal distribution system, which is approximately a 10% of the water being distributed.

Solar decathlon 2015, NexusHaus by the University of Texas at Austin

Solar decathlon 2015, NexusHaus by the University of Texas at Austin

The rainwater is collected from the slightly steep roof and canapé on the deck. It is then treated with a screen in order to get rid of the large debris and collected in a primary tank for storage. From the primary rainwater collection tank it either goes to be used as consumption in the potable water system or it transfers to the rainwater thermal storage tank. The potable water system is provided with a pump that leads the water to the filtration system, which treats water to potable water standards so that it could feed the domestic water system and then distribute it to either the hot or cold water.

The NexusHaus is also provided with a grey water tank that collects the water from the bathroom sink, the shower, and the clothes washer. This is useful in order to reuse it for irrigation and gardening systems because, although is used water, it preserves standard conditions for this functions. On the other hand, the backwater tank or the sewer collects the water from the dishwasher, and the toilets and the kitchen sinks. This water would be unsafe to reuse because of its high levels of organic matter.


Analysis of the results

One of the mistakes that the team made was designing the system from a worst-case scenario point of view, which followed the Texas Water Development idea of fulfilling 25 gallon of water per day per person. As a result, the system in the SD NexusHaus not only had the rainwater roof but the entire canopy in the deck as waters collectors. That led to all kinds of engineering, time and economic problems. Therefore, it was able to collect up to 8000 gallons of water per year, which is more than the amount of water that is needed for this case. In conclusion, it is clear that the system was a success and the team was able to achieve collecting and reusing a large amount of water. However, the result did not fit this case.


WaterShed by the University of Maryland, Solar decathlon 2011

WaterShed consists of two rectangular modules with designed split-butterfly roof that help capture rainwater. Constructed wetlands that are center of the house can filter rainwater and grey water for reuse. One of the roofs have a green roof, which is able to retain storm water and reduce the heat island effect. Another roof has photovoltaic panels and plays a major role in producing enough energy from the sun. In addition to this systems, WaterShed has a vertical garden that provides shade and keeps temperature moderate in the summer and also has an edible landscape, producing nutritious food for sustainable living.

WaterShed project Diagram

WaterShed project Diagram


The average American used 100 gallons of drinking (potable) water in his or her home per day. More than half of that was used outdoors to maintain landscaping, while 50-80% of the wastewater produced inside a home was classified as grey water. In WaterShed, it deals differently with potable water, rainwater, greywater and black water. Collected rainwater from the roof replaces potable water’s role for irrigation. All grey water from bath sink was captured and filtered in wetlands, which broke down nutrients and removed pathogens. Its water management had plans to reduce demand for potable water and anticipated saving the homeowner and the community money.


Green design strategies

WaterShed projects have two specific green design strategies: one is constructed wetlands, which plays a role of an artificial filtration, and another is a green roof. The filtration wetlands that are located to bathroom remove pollutants (such as soap) from grey water. The project also uses plants in ‘retention wetlands’ to keep the stored water clean.


Its south module has a green roof about 312 square feet. It plays a major role of capturing rainwater and also decreasing heat island effect. With a green roof system, it can filter pollen and pollutants from the air and be attributed to keep the surface as an insulation material.


Viewpoint of aesthetics

WaterShed’s roof is not only a functional envelope but also has an aesthetic role. With inclined roof design, it could make inner spaces’ environments comfort. The wetlands which are in between two split-roofs produce private spaces for people to use for resting places with the water. With this water system, people would be able to feel comfortable and live in a natural environment with edible plants.

Western Elevation of WaterShed project

Western Elevation of WaterShed project




Water is a limited natural resource that provides the development of life on Earth and, as a result of factors such as globalization and industrialization, its perseverance has been put on risk. Therefore, in response, it is our responsibility to work towards developing a sustainable system in order to preserve and manage a rational use of water resources. By investing in a rainwater collecting system, not only can individuals take advantage of harvesting their own resources for personal use but they may also help prevent the global water crisis by avoiding the use of traditional groundwater resource.

In order to develop the most suitable system for every case, we must research into new technology systems, such as cleaning filters or water pumpers. However, most importantly we must take full part on the design process; by working on the design, we are able to find a bigger range of opportunities and we can focus on more particular cases, such as the example on the NexusHaus in which the rainwater collector also becomes a solar protector. It is important also to not forget the context in which we are working and understanding the necessities so we can make the best decisions concerning the amount of water collected, cost or visual impact. Therefore, the amount of opportunities that rainwater collecting systems can bring us depends mostly on how we select the most suitable system and how we adapted to the building by focusing the design process.




Novak, C. A., Van, G. E., & DeBusk, K. M. (2014). Designing Rainwater Harvesting Systems : Integrating Rainwater into Building Systems (1). Somerset, US: Wiley.

Cantor, S. L. (2008). Green roofs in sustainable landscape design (1st ed.). New York: W.W. Norton & Co.









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