The largest "Effizienzhaus-Plus" rated building is now standing on Frankfurt's Speicherstrasse. The 78-unit apartment building developed by ABG Frankfurt is to produce more energy with its solar panels than the building's occupants use. Architect Manfred Hegger, a pioneer in energy-efficient buildings, originated the idea for the project near the Westhafen area. The "Aktiv-Stadthaus" is part of the Effizienzhaus Plus network guided and subsidized by the Federal Ministry for the Environment, Nature Conservation, Building and Nuclear Safety. The network currently contains more than 30 residential projects.