The first floor of the RSF had to be constructed above grade because the site has expansive soils. Early in the design process the team conceived that the below-grade crawlspace formed by the foundational piers could be used to precondition ventilation air - storing heat from the transpired collectors and data center and delivering it when needed in the heating season and removing heat in the cooling season after nighttime precooling (Torcellini et al. 2010). This crawlspace is referred to as a remote-mass labyrinth because of its maze-like appearance. To model energy savings, it was divided into sections defined by the piers and finite difference heat transfer nodes defined to represent the slab perimeter, slab center, perimeter walls, and the grade beam. Nodes representing the earth below the slab and outside the perimeter walls were also included, and in turn were connected to boundary conditions of the undisturbed ground surface temperature for the perimeter and constant deep ground temperature below the slab. Air nodes were included to complete the energy balance. The energy flows were then calculated using a spreadsheet program for 8,760 hours of the year to characterize the heat exchange between concrete and air (neglecting the heat capacitance of the air nodes). The separate data center and transpired collector calculations provide a schedule of available temperature and flow rate from those two heat sources. The ventilation system is designed to deliver space-neutral air, so the flow rate from the data center and transpired collector and the mixing with outdoor air can be controlled to deliver 68ºF air at the volume needed to meet ventilation requirements.