A person-support surface comprises a non powered mattress and a coverlet positionable on the non powered mattress. The coverlet includes an entry positioned at a first end of the coverlet, an exit positioned at a second end of the coverlet opposite the entry, an upper air impermeable layer, and a lower air impermeable layer coupled to the upper air impermeable layer to form an air flow path along the coverlet between the entry and the exit. The upper air impermeable layer is a vapor permeable and the lower air impermeable layer is a vapor permeable.