Every time it rains, this concrete house turns into an oversized water filter.
Rainwater runs from the roof through a custom-designed system and ends up in a cistern, clean enough to drink. A demonstration building was on display during Milan Design Week last month, complete with a fake cloud overhead to show it in action.
Using rainwater to supply drinking water could be "the missing link for ecological housing," says Katalin Ivanka, creative director for Ivanka, the Hungarian company that designed the Rainhouse system. While it’s becoming more common for buildings to capture rain to water plants or flush toilets, even the greenest buildings still tend to use water from the tap for drinking and cooking.
In cities, where rain rushing down streets can lead to flooding and overflowing sewers, new rain-harvesting buildings could serve as an alternative form of stormwater management. In countries that get plenty of rain but lack safe drinking water, the buildings could act as water treatment plants. The company also envisions the system scaled up for use in "rainwater factories" to supply pure water for manufacturers.
Here’s how it works: Falling rain is redirected through a series of filters, starting with a patented material called "bioconcrete" on the roof. Specially designed stainless steel pipes filter out more contaminants before the water lands in a cistern.
"The bioconcrete cistern has a key role in the process," explains Ivanka. "It acts like a natural limestone cave formation, and orients and sets the pH to the ideal range. It further softens the otherwise naturally soft rainwater." A silver surface on the tank keeps it clean, and a final set of filters take care of the last step of purification. No chemicals are used.
The technology can be added on to an existing roof or incorporated into new designs. It can also be customized for any size of building, from a single-family home to a plant that manufactures food. Of course, it doesn't work everywhere—if a city doesn't get adequate rain, the building won't be able to harvest it. The company estimates that it could be used in about half of the world's countries.
"Less and less freshwater is available on Earth, but we need more and more of it," says Ivanka. "Unlike oil, it can't be replaced by other materials." The company plans to license the technology everywhere, and to make part of the technology available open source.
Despite the company's environmentally minded motivations, though, they have at least one blind spot: They're planning to start using the buildings to make bottled water.