Hi KentS,
I think that the OP was asking more about mattresses than a mattress protector.
Having said that … the thinner membrane type mattress protectors like the Protect-A-Bed protectors (see post #89 here) are certainly a popular choice and the viscose/rayon (from eucalyptus) fabric can help with moisture wicking but for some people the semi breathable membrane in these types of protectors can impair airflow enough that they can sleep warmer than they would with other types of protectors without the membrane that are more breathable.
Phoenix
PS: I removed the link from your post