As mattress protector manufacturers we often come across the issue of breathability, because this has a direct effect on the comfort of the mattress protector.
Let's start with why breathability is important. If you look at a normal piece of fabric like a fitted sheet or a shirt you can see that the fabric is either woven or knitted. The individual threads are seperate from each other and as the fabric moves and stretches these threads move away from each other creating a gap. This gap, no matter how small allows air and molecules to pass easily through.
If you then do something to make it waterproof then you are creating a barrier that not only holds the threads together but also stops anything from passing through, that is after all what you want isn't it? You want to stop liquids from getting through to your mattress.
The downside of this is that you have now seriously affected it's breathability, potentially making it hot and sweaty to sleep on. As soon as you compromise the breathability the heat and moisture that your body produces has nowhere to go. Moisture accumulates beneath you where your body is closest to the waterproof layer, this increases your body heat as the heat cannot easily disipate and the sweatier you become.
So any sort of non breathable waterproofing will have this effect, so a PVC or plastic membrane will do this.
We also get asked, How can something be both breathable and waterproof at thje same time? It does sound strange yes how can it be breathable and yet still stop water from passing through?
Well if you look at your own skin, you have exactly that. The blood and fluids inside you stay there unless you are cut or scratched, but you can still perspire through your skin. So how is that possible? Well it comes down to molecular engineering. Some molecules are bigger than others, the bigger ones are too big to pass through so liquids cannot pass through because they are too large but vapour molecules can pass through because they are smaller.
Perspiration actually comes in two forms. When you sweat the liquid isn't actually passing through your skin, it is being secreted by sweat glands in your skin. This is the body's way of cooling, the sweat cools in contact with air which then cools your body. However perspiration also comes in the form of water vapour passing through your skin and reforming as a liquid on the outside.
So water molecules are too large to pass through but vapour molecules are small enough to pass through. So in terms of mattress protection breathability we are talking about the ability to stop water molecules passing through whilst still allowing vapour molecules to pass through.
This ability for vapour to pass through is what stops you from getting hot and sweaty.
So back to our original question, which is the most breathable mattress protector? Very few waterproofing materials actually have this ability to allowvapour to pass through, however the one that can is called polyurethane, sometimes just referred to as PU. Polyurethane is completely waterproof yet breathable. But it isn't quite a simple as that because some polyurethane is less breathable than other polyurethanes.
Let's just clear that issue up. It comes down to the thickness of the polyurethane. I'm sure that you can imagine that the thicker the layer of PU, the less breathable it is. If it was an inch thick it wouldn't be breathable at all, so the thinner the layer can be made, the more breathable it is, and consequently the more comfortable it is. So it's not just about the waterproofing being made from PU, it's about how thick it is and then how it is applied to the fabric. So finding one that uses PU is half the battle but very few manufacturers elaborate any further than that. They might not want you to know the downside of their particular PU product.
Polyurethane has to be applied to the underside of the fabric. The cheap and cheerful way to do this is to paste it on in liquid form. It's a quick, simple and cheap way to get PU onto the fabric. However this method creates an uneven layer. Some parts will be thin, some will be thick, some areas will be breathable others will not, so some parts will make you sweat, others won't, but you have no way of knowing. If a PU mattress protector seems quite cheap, a bit of a bargain, then this is probably the method used and you may as well not have chosen a PU protector. Of course the manufacturer won't say that this is the method used, and the retailer probably doesn't even know that this is an issue.
The better way to apply PU to a mattress protector is in the form of a pre made laminate that is completely consistent in thickness at every given point. This ensures that the breathability is the same at any part. This is how we produce our PU mattress protectors. This microfine membrane is bonded to the underside to produce perfect breathabilty making it the most breathable mattress protector available. This is our Allergon Waterproof Mattress Protector. Use the link below to find it.