Summary: 355 Eleventh, San Francisco, is an historic and previously derelict turn-of-the-century industrial building now refurbished to be as beautiful as it is energy efficient. Part of this refurbishment is a new corrugated skin to replace the original, historically significant steel cladding. The skin is perforated with small holes designed to allow light and air to pass through new windows hidden behind it. This perforated barrier controls solar heat gain while enabling cross-ventilation of the interior. The double-skin façade becomes a screen for sunlight and air while maintaining the stoic, industrial character of the original building. Behind that screen new, operable windows allow user control of airflow. The final building received Gold-level LEED certification.