A nonintegrated mattress topper comprises a cover at least part of which comprises a fabric having a variable vapor transfer property. When the fabric temperature is within a first range consistent with the presence of an occupant on the mattress the fabric exhibits a first vapor transfer rate sufficiently high that the fabric is permeable to vapor transport across the fabric, and when the fabric temperature is lower than the first temperature range and consistent with the absence of an occupant the fabric exhibits a second vapor transfer rate lower than that of the first vapor transfer rate. Also disclosed is an occupant support assembly comprising a mattress and a nonintegrated topper having the variable vapor transfer property. Also disclosed is an occupant support system comprising a mattress and an integrated topper at least part of which is made of a fabric having the temperature dependent vapor permeability.
