The usual way to add solar power to a building is just to attach some panels to the roof. But a new design goes a step farther with a solar attachment that doubles as extra housing. A single story of lightweight apartments are added to a rooftop and then covered in enough solar panels to generate power for the entire building.
For cities like San Francisco that are struggling with rising rents, the design has the potential to quickly provide some new homes—all without developing new land or changing city regulations about building height.
The OnTop design comes from a student team in Germany, a country where 70% of the population lives in cities and there's also a housing crunch. "New living space is needed and the question is where to build it," says Sebastian Fiedler, the professor at Frankfurt University of Applied Sciences who advised a team of architecture, business, and engineering students. "Building on top of an existing building doesn't take up new land, and no additional infrastructure has to be created."
The idea also takes advantage of new money flowing into a city to help renovate older buildings for long-time residents; renting or selling the new living units will directly fund upgrades for everyone else. "Many people want to live in the city and they are willing to pay a lot of money for it," Fiedler says. "It is a powerful economic force. We want to use this force to enhance the existing building."
Germany is aiming to make all buildings "climate neutral" by 2050, which will require a huge amount of renovation. Many projects could cause rents to rise, but the designers believe their system can help avoid gentrification by paying for itself. It also gives new people moving to a city the chance to live in older, established neighborhoods—instead of new developments in the suburbs— without the guilt of displacing long-time residents.
In Frankfurt, where the team will build its first set of new apartments on an existing building, the system will generate 40,000 kWh of electricity per year. Along with solar panels to generate electricity, the system also uses solar collectors and heat pumps to provide heat, so the whole building can run on renewable energy.
The design won first place in the "social housing" category of the recent Solar Decathlon Europe.