Hi CJW,
There is more about the pros and cons of different types of mattress protectors in post #89 here but it wouldn’t be overkill because a quilted mattress cover and a mattress protector perform completely different functions.
A quilted mattress cover (or any cover) is part of the mattress itself and plays a significant role in the feel and performance of your mattress as well as its temperature regulation and the surface or “hand feel” as well. It isn’t designed to be removed and cleaned on a regular basis as easily as a mattress protector.
A mattress protector on the other hand is not meant to be part of the mattress itself and is meant to protect the mattress (including the cover) from the body oils and fluids that we release each night and guard against spills and accidents that can stain the cover and void a warranty. The goal of a mattress protector is to have as neutral effect on the feel and performance of the mattress as possible (including temperature regulation). Unlike a cover … it is meant to be easily removed and cleaned on a regular basis so that you can maintain a clean and hygienic sleeping surface.
A mattress protector isn’t meant to provide the benefits of sleeping on thicker layers of wool as much as to make sure that the benefits of the wool that is in your cover aren’t reduced more than they need to be. If you put a semi breathable layer (such as a membrane type protector) over a wool quilted cover then there would be less airflow through the protector and this can reduce the benefits and effect of the wool underneath it.
There is always a tradeoff between the different functions that a mattress protector is meant to provide. One of these is the degree of water resistance that is important for each person and their circumstances. The second is the effect on the feel and performance of the mattress (thicker less stretchy protectors will affect the mattress more than thinner more stretchy protectors). Finally there is the effect on temperature regulation and airflow (more airflow and moisture wicking will have less effect on the temperature regulating properties of the mattress than less airflow and less moisture wicking).
For those who need a waterproof sleeping surface then the membrane types of protectors would be the likely choice but the tradeoff would be that it would have less airflow and reduce the temperature regulating benefits of the wool underneath it. It will also have a fairly neutral effect on the feel of the mattress.
For those where “water resistant” is good enough and are more focused on keeping the full temperature regulating benefits of their mattress cover then a wool/cotton protector with thinner layers of wool may be the best choice because it wouldn’t interfere with the temperature regulation properties of the wool underneath it but the tradeoff would be that it will have a little larger effect on the feel of the mattress because it’s thicker.
For those where a protector that only absorbs excess body fluids and oils would be OK even though it wouldn’t protect against spills and accidents as well (they may go through to the mattress if the fluids penetrate the protector) or offer enough protection for those who tend to perspire much more at night, then a stretch cotton protector may be their best choice because it would only have a minimal effect on the feel of the mattress itself and would still allow for good airflow and moisture wicking to maintain the temperature regulating benefits of the wool quilted cover.
So the goal of all mattress protectors is to “protect” the mattress to different degrees while having the least possible effect on airflow and temperature regulation and on the “feel” of the mattress and which of the tradeoffs involved with each of them would be most important would depend on each person’s circumstances and criteria. There isn’t a mattress protector that has the “best” of all three.
Phoenix