Are Modern Cloth Nappies & Nappy Covers REALLY Breathable?

Many people seeing modern cloth nappies for the first time and hearing about the waterproofing used in most of them - PUL or TPU - are sceptical that a fabric can be both waterproof and breathable at the same time.

While there are options offering much more breathability (like wool covers or a fitted nappy with no cover), there is no doubt that PUL has revolutionised the cloth nappy industry. But is it really all that much better than the old plastic & PVC covers?


We’ve got to clarify what ‘breathable’ means, first. It doesn’t mean that if if you held a nappy cover over your face you’d be able to breath through it. And it doesn't mean unobstructed airflow. It really refers to the structure of the fabric on a more microscopic level. PUL or TPU has micropores in the fabric that are big enough to enable the release of heat and water vapour, but the fabric remains waterproof as the micropores are still thousands of times smaller than a water droplet. Its structure reduces the heat and sweatiness that was a problem with the old plastic pilchers, resulting in a fabric that is waterproof, yet more comfortable to wear.

Not convinced?

Here’s a little experiment we did, comparing the breathability of a PUL cloth nappy cover with plastic cling wrap to see whether water vapour can actually pass through PUL. As water vapour is invisible, we needed some way to trap the vapour and convert it to condensation once it had passed through the cover. A martini glass seemed ideal!