Fast Company's Adele Peters takes a look at a new 162-unit apartment complex planned for Heidelberg Village in Germany, which will soon be the largest passive house development in the world.

Designed by local, sustainable architecture firm Frey Architekten, the complex will never use more than 15 kilowatt-hours of energy for heating per square meter in a year. In comparison, a standard building uses about 100-300 kWh.

"The reason is the volume to surface ratio," says Wolfgang Frey, head of Frey Architekten, the sustainable architecture firm that designed the complex. The buildings—one five stories high, and the other ranging from five to eight stories—are plastered with energy-producing solar panels on the facades, not just on the roof.

The placement of the panels and the buildings also helps save energy. "Because we are able to produce shade with the solar panels, it has a dual purpose: energy production all the time and cooling in the summertime," he says.

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