Designing an immune building from the ground up is invariably a superior approach and can produce a cost-effective design with many options for controlling indoor aerobiology and protecting against both natural and man-made releases of biological agents. IBSI can provide consultation and design support for buildings in the design phase and implement systems that might not be possible as retrofits. Compartmentalization, isolation systems, pressurization, and buffer zone systems can be designed for new buildings with greater ease than they could be implemented in existing buildings and at considerably lower cost.