Hi ckollars,
Thank you for your forthright reply … and I agree with you that these types of issues should be discussed more openly because they are a fact of life for millions of people.
It may be worth considering other alternatives that would provide better ventilation and temperature regulation and “comfort” and help you sleep better than than using a plastic/vinyl bag. If you were to use a membrane type mattress protector that is waterproof on 5 sides and tucks under the mattress like a fitted sheet (see post #2 here for some options) and then use a wool/cotton mattress protector on top of that (see post #89 here for some options) you would have a two protector system where both would be easy to remove and washable and would likely have enough water resistance to protect your mattress and you would have a more breathable and probably more comfortable sleeping surface as well.
Other alternatives that are also included in the main mattress protector post would be the wool/cotton protectors that include a waterproof membrane or a wool “puddle pad” under a membrane protector.
These would be more costly options than a plastic/vinyl bag but they would probably be much more temperature regulating and comfortable as well.
While I don’t have any personal experience with it so I don’t know “how waterproof” it is … there is a newer type of Crypton mattress protector made by Legget & Platt that may also be worth considering. I have some samples of the regular Crypton fabrics that are very stiff and not very breathable at all but it looks like the version they are using in the protector is much more flexible. I also don’t know if only the top surface is waterproof or whether it is waterproof on 5 sides.
Phoenix