Why the Membrane Isn’t Breathing

In our travels, daily training with the dog, time at the shooting range, biking, or even walking to the store – we often wear clothes made with so-called membrane fabrics. But does a high-end outdoor jacket with the best membrane guarantee dry skin and effective sweat evaporation? No. And this article explains why. This isn’t a technical manual. It’s a practical take on why and when membranes stop working. There are no formulas here, just real-world examples. It’s not an attack on manufacturers either. Membranes make sense. But they work because of physics – not magic.

Do Membranes Really Breathe?

The first modern membrane was created in 1969 – a microporous, expanded Teflon structure we now know as Gore-Tex. Each square centimeter contains about 9 billion pores. These are small enough to block liquid water, but large enough to let water vapor pass through.

In short: -Water stays out. -Vapor can escape. But only if conditions allow it.

The Funnel and the Needle – A Simple Explanation

Imagine a huge funnel – one meter wide – ending in a needle as thin as one used for premature infants. Absurd? Yes. But useful as a metaphor. You’re wearing a sealed rubber suit and start to move. You sweat. Now pierce the suit with that needle. Water vapor starts to escape. Now pour water into the wide end of the funnel. It blocks everything. Nothing passes through the needle. That’s what happens when your jacket is soaked – the pores get clogged and stop breathing.

What is DWR?

DWR stands for Durable Water Repellent – a coating applied to outer fabrics. It helps water bead up and roll off instead of soaking in. DWR doesn’t directly affect the membrane, but without it, the membrane can't do its job. Once the fabric absorbs water, pores get blocked. DWR wears out. It’s broken down by: - dirt, sweat, oils, - washing with regular detergents, - overheating during drying, - skipping post-wash reactivation. How to care for it: - use proper cleaning agents, - avoid fabric softeners, - reactivate with low heat (tumble dry), - reapply waterproofing treatments regularly.

In Practice

Step out into the rain. -If your jacket is dry – the membrane works. -With heavy rain and fresh DWR, it still works, but less efficiently. -Once the fabric is soaked, breathability drops to almost zero. You’ll stay dry from the outside, but wet from the inside.

What About Footwear?

Shoes are an even tougher case. If: - it’s dry, - the shoes are made of fabric (not leather), - no heavy insulation, - and you wear the right socks, then... the membrane might work at 10–25% of its theoretical performance. If: - the shoe is leather, - soaked by wet grass, - worn for long hours, then... it doesn’t breathe. Or works so poorly it’s irrelevant.

Clothing (Jackets, Pants)

Condition	Works Well	Reduced Function	Does Not Work
Dry jacket, functional DWR	yes
Temperature/humidity gradient	yes
Slightly damp jacket		reduced function
Minimal difference in temp/humidity		reduced function
Soaked jacket (DWR failed)			does not work
High ambient humidity			does not work

Footwear

Condition	Works Well	Reduced Function	Does Not Work
Dry fabric shoes	yes
Low humidity, proper socks	yes
Thick leather or insulated boots		reduced function
Wet conditions, grass			does not work
Shoes soaked through			does not work

Shelters (Tents, Tarps, etc.)

Condition	Works Well	Reduced Function	Does Not Work
Dry climate, good ventilation	yes
Internal condensation (breathing)		reduced function
High humidity, no airflow			does not work
Soaked outer layer			does not work

Breathable Dry Suits :) ?

Some manufacturers now offer dry suits made with membranes – marketed as breathable. But the term deserves a closer look.

When Membrane Dry Suits Can Release Vapor

1. The suit is dry and not under water pressure (e.g., on surface breaks). 2. Clear difference in internal vs. external temperature. 3. Used in humid but non-submerged activities (kayaking, SAR).

When It Won’t Work

1. While diving – water pressure blocks diffusion. 2. The outer fabric becomes saturated. 3. Inner layers trap vapor before it reaches the membrane. 4. Extremely humid environment – no vapor pressure gradient.

How to Spot Truly Breathable Membranes

Just because a label says “breathable” doesn’t mean it is. Look for: - RET values (below 6 = excellent breathability), - Independent testing (e.g., Öko-Test, EMPA, Stiftung Warentest), - Intended use: alpine, ultralight, ski-touring gear uses better membranes (e.g., Gore-Tex Pro, eVent DVAlpine), - Construction: 3-layer laminates with minimal insulation breathe better. Manufacturers like Arcteryx, Montane, Tilak, Patagonia, Brynje, Fjällräven (Eco-Shell), or Hestra (gloves) tend to use materials that really breathe – but even they won’t work in all situations.

Conclusion

A membrane is a tool – not a magic shield. It works when conditions allow. Understand those limits, and you’ll be less likely to blame your gear.

High-end membranes, even the most expensive ones, offer great durability and breathability – but they still follow the same rules of physics.

If a membrane gets blocked by water, it stops breathing – whether it costs $2 or $1000. So think carefully about how and where you’ll use it – and choose accordingly.