Breathability - Fact or Fad?

Research into the test methods available to measure "breathability" has led to the question of whether breathability in performance waterproof clothing is a real issue or a perceived marketing premium.

Keela has been researching and examining the issues surrounding breathability and the REAL physical effects it has on our performance clothing.

We went back to the early 50's and 60's when PVC and PU fabrics were a popular choice for protection against wind and rain. These fabrics did not allow moisture to pass through to the outside therefore creating an uncomfortable wearer environment. A breakthrough came in the 70's, with the discovery of microporous coating, which allowed moisture vapour to pass through, and as a result sustained a more comfortable wearer environment. This was an innovation of its time and soon many other materials followed, including the introduction of Hydrophilic breathable PU. But they all had one major problem. They did not perform in wet and cold conditions - the very conditions they were designed for.

The formation of dew point occurs during rain conditions and when the outside temperature is low (between 0ºC and 10ºC) In these conditions rapid build up of condensation will result. A warm body at 37ºC inside a garment with cold saturated air outside will struggle to cope with the moisture build up, leaving the wearer uncomfortable.

Another problem is that these systems perform adequately during low-level activity but when used for more than one hour at higher levels of activity the performance starts to break down.

When analysing the independent wearer trials and research the results demonstrated that after 60 minutes all the material systems on test performed almost the same. This proved that whether you had purchased a microporous or hydrophilic garment at £60-£70, you would struggle to physically feel any difference between this less expensive product in comparison with one purchased at £120+, for example a bi-component jacket .

TEST METHOD

The test standards for measuring MVT (moisture vapour transmission) rates through waterproof fabrics, whether they be coated or laminated, has an extremely fundamental failing, in that it tests without any temperature gradient e.g. 35ºC outer temperature, 35ºC inner body, 50% humidity and NO RAIN. Is this realistic?

CASE STUDY

One of the most interesting studies carried out was by a former student at Leeds University , Julie Gretton, who was probably the first to conduct a proper trial of how various fabrics performed in rain and also stressed how important the formation of condensation was inside our clothing systems.

Wearer trials conducted by Leeds University :

Wearer trials were carried out using humidity sensors. Three different waterproof fabrics were used in the trial. Microporous, Hydrophilic and Bicomponent. The tests showed that 100% relative humidity was attained by the microporous jacket after just 20minutes, the hydrophilic in 48 minutes, and the bicomponent jacket in 60 minutes.

The same jackets were worn in an all day mountain field trial and also monitored by humidity sensors telling the same story. During the morning, rain caused the jackets to succumb to condensation in the expected order but although the rain ceased, the microporous and bicomponent jackets maintained 100% relative humidity for the rest of the trial and condensation remained. The hydrophilic laminate showed condensation before the bicomponent, but later recovered by absorbing the condensation when the rain ceased and its microclimate fell to 90% relative humidity.

So the hydrophilic did perform better under these conditions than the others but still retained 90% relative humidity. Still uncomfortable for the wearer.

How do we deal with the problem of Condensation?

Condensation cannot be eliminated completely but we can reduce it. One way in which to deal with condensation is to use combinations of materials. Many were tried before finding the ideal combination, which seemed to work. The best results were achieved by using 2 hydrophilic membranes with an air gap in between. The inner hydrophilic layer was laminated onto a high wicking inner liner to absorb liquid moisture away from the body and create a separate layer to deal with the liquid moisture while the outer hydrophilic coated fabric. (See System Dual Protection® page)

Research by Niederrhein University of Applied Sciences:

The tests show that System Dual Protection performs better than PTFE in more realistic conditions. Ms Gretton conclusion also suggests, that neglecting to study the behaviour of fabrics under rain conditions will not lead to future improvements in real time performance.

Unfortunately the word 'breathability' has been wrongly marketed. The consumer is led to believe that breathability is the essential element in the performance of our wet weather clothing but it has been proven that moisture vapour transport (breathability) decreases in rainy conditions. This is partly due to the rapid build up of condensation that occurs and should be considered when testing waterproof fabrics.