In 1943, in the midst of the Second World War, the famous architect Richard Neutra was commissioned by the government of Puerto Rico to build hospitals and schools. In response, he produced a number of prototypes and processes investigating different ways to ventilate and climate control buildings in the sub-tropical environment of the island through technology. Neutra famously labeled his work in Puerto Rico a Planetary Test. This article examines this history of making climate a medium for design and the implications of these practices for our present