The Gore-Tex membrane is one of the best-known membranes in outdoor clothing. It is now used in raincoats, trousers and hiking boots. According to manufacturers, the products are windproof, waterproof and breathable.

Sounds good, right? Unfortunately, there is – as is often the case with big promises – a small catch, which you should consider before the purchase of membrane products in general …

But first, how does the Gore-Tex membrane works.
The membrane has 1.4 billion microscopic pores per square meter. These pores are about 20,000 times smaller in diameter than water droplets and are therefore too small to allow moisture to penetrate from the outside.
Water vapor molecules, on the other hand, are significantly smaller. They can easily diffuse through the pores to the outside. Sweat can thus be transported away from the body.
This is precisely where the breathing activity is concerned, however, there is just one fact to keep in mind.

The transport of the water vapour molecules is only possible if the temperature in the pants, jacket or shoes is 15°C above the outside temperature.
To make it simple, it must be colder outside than inside.

The human body core temperature is 37°C. However, the skin temperature may deviate strongly from this value. At an air temperature of 15°C, the average skin temperature is only about 24°C.
This reduces the difference between the outside temperature and your body temperature values and thus the present concentration gradient, which is required to transport perspiration away from the body.
As a result, the breathing activity is hardly or no longer present if the temperature differences are too low.

What does that mean for me?
In warm regions, it is not possible to transport sweat away from the body, through the membrane to the outside. The respiratory activity is severely restricted – in the worst case no longer present.
It is fair to say that all membranes on the market have this deficiency since they all work the same in principle.

However, in regions where the temperature difference between inside and outside is given a garment with membrane clearly has its advantages.
Before a purchase should be very carefully considered in which regions it should go.
On a trip to the tropics you can save money for an expensive membrane jacket – a plastic bag is just as breathing-active in this area.