Pilae Stacks

Pilae Stacks are stacks of pilae tiles, square thin tiles, that were used in Roman times for the underfloor heating system, common in Roman bathhouses, called the hypocaust. The idea of the Pilae Stacks is that the floor is lifted allowing air to freely move underneath and up, through the hollow bricks, into the walls.

This was the first form of underfloor heating and the same principle is still used today.