Beginning with the ideal of a cloud, the lightest and most economical source of summer shade, PSi uses air as a structural medium to inflate and suspend diaphanous volumes of ultra-lightweight fabric over the concrete and gravel courtyard. The geometric form of the torus, a perfectly efficient pneumatic shape, provides the basic unit that is repeated, interlinked and modulated to form a hovering cloud. As with a true cloud, microclimates of shade and sun; humidity and dryness are created. Patterns of overlapping shadows animate the hard surfaces of the courtyard, providing respite from the sun on a hot day while apertures in the centers of the translucent toruses, like gaps in passing clouds, frame views of the sky above. Widely varying in size and height, the toruses are subtly deformed by internal pressure in response to the various activities of the shady space below: reclining, splashing, sunbathing, chatting. Concealed strips of clear material sewn into the fabric activate the glowing volumes of the inflatable with slowly moving arcs of sunlight.In contrast to past installations, PSi will be prefabricated offsite and installed in a matter of hours. Contemporary fabric cutting and assembly technologies will allow for the direct use of the architect’s digital files in the fabrication process. In its entirety, the material and equipment necessary for the installation will weigh less than one ton and amount to a single load on a pickup truck. Field labor will be minimized, no scaffolding required, and waste negligible. For the duration of the installation the small amount of energy necessary to power the fans will be offset by electricity generated by air, in the form of wind, at a site in upstate New York. Finally, in a departure from past approaches, the project is designed to be easily redeployable, and will have a life beyond the approaching summer.