Yokota Air Base (YAB) has been extensively developed since its construction in 1940 by the Japanese Imperial Army (JIA) as an airfield. Typically, older buildings would be demolished to make room for future growth, but the host nation has rules set forth for YAB that prevent demolition until buildings have reached a certain age. With demolition out of the question and no room for purpose-built architecture, YAB had to look at their existing buildings. The YAB Admin Conversion Study provides various courses of action (COAs) to transform vacant housing units into administrative buildings. This adaptive reuse study is a model of sustainability because it leverages embodied energy in the structures, saves energy wasted in new construction, and generates less construction refuse. The planning team investigated three COAs ranging from short-term solutions to longer full-scale renovations to create the most optimal and flexible administrative solution. The study included a DD Form 1391.