“Breathable.” “Air permeable.” Why the confusion?

At first glance, both breathability and air permeability seem to answer the same question: Can this material breathe? Marketing jargon often blurs these lines, but we think it’s time to clear the air.

Breathability: Letting sweat vapor escape

Breathability refers to how effectively a fabric allows water vapor (like – evaporated – sweat) to pass through it and escape.

• Measured as: Moisture Vapor Transmission Rate (MVTR), typically in grams of vapor per square meter, per 24 hours (g/m²/24h), yes, that’s per day.
• Standards used: JIS L 1099 A1 and ASTM E96, among others.

Imagine hiking uphill: you start sweating. A breathable jacket helps that vapor escape instead of collecting inside your jacket, where it would make you feel damp and sticky.

But wait, 24 hours? Isn’t that too long?

Yes, it is too long indeed. When you’re active, you need moisture to escape quickly. The “24-hour” measurement doesn’t indicate actual drying time. Is just a way to compare materials under the same conditions. It’s about how much vapor can move through over time. Higher numbers = faster moisture escape.

And yes, using a 24-hour unit does yield higher, more marketable numbers.

If we do the math and turn it into minutes instead of days.

20,000 g/m²/24h = ~13.89 g/m²/min

Because “20,000” sounds impressive and makes comparisons between fabrics easier. If brands used 13.89 g/m²/min, it would still be meaningful, but the number feels less dramatic and harder to contextualize for most readers. What is key here is how it’s measured. But that’s another story.

Air permeability: Letting air pass through

Air permeability is about how much air passes through a fabric, and how quickly.

• Measured as: L/m²/s or CFM (Cubic Feet per Minute)
• Why it matters: This affects how windproof a fabric is. More air = more ventilation, but also more chance of getting cold in windy conditions.

Here’s the big difference (while testing)

Breathability: Vapor moves slowly, so breathability is measured over hours.

Air permeability: Air moves fast, so air permeability is measured in seconds or minutes.

They’re not directly linked. A jacket can be:

• Breathable and air-impermeable → keeps you dry and blocks wind (like dimpora® membranes)
• Air-permeable and breathable → feels breezy, but might not protect against cold or rain as well

Why are dimpora® membranes breathable but air impermeable or windproof?

These properties, while related, are measured differently. High air permeability usually implies good breathability, but the reverse isn’t necessarily true. dimpora® membranes are highly breathable yet have low or no air permeability (they are windproof) because of how moisture diffusion works.

Our membranes are full of tiny, twisty pores that let vapor escape, but stop air and water. This means:

• High breathability to keep you dry
• Low air permeability to block wind and stay waterproof

Air permeability tests push air fast through the fabric. But our small pore structure resists that airflow. That’s why we’re breathable but also windproof.

Could we make them air-permeable?

Sure. If we wanted more airflow, we’d design membranes with larger, straighter pores. But we’d have to give up some waterproofness and wind protection. It depends on what you need your gear to do.

How dimpora approaches breathability and air permeability

• Our membranes use carefully engineered microporous structures balancing breathability, waterproofness, and windproofness.
• We prefer the ASTM E96 standard, as it closely mimics real-world conditions.
• Whether you’re designing gear for alpine expeditions or trail runs, understanding the distinction between these two properties is crucial.

At dimpora, we believe that transparency in language leads to better decisions and better products.

Ready to dive deeper?

Let’s talk membranes, materials, and perfecting performance for your next collection.