Existing buildings present unique challenges, the Oesterle Library is no exception. Oesterle is a three-story 28,000 sf building that was expanded and modernized under this project. Callan Consulting Engineers performed extensive site surveys and analyses to develop a solution that minimized cost and downtime with a phased approach. CCE reconfigured mechanical systems to enable comfort and control of new and additional heating and cooling zones. A new boiler plant was installed to replace a district steam heat exchanger, and all major equipment was relocated onto the campus-wide BAS. Electrical power and lighting controls were designed to accommodate new offices and a new layout of equipment and furniture. CCE also developed a replacement fire alarm panel to fulfill the current code requirements. Plumbing and fire protection design had to accommodate new restrooms and new building additions. As a result, the occupied space was transformed, and the existing infrastructure was successfully reutilized.