What is a Breathability Rating?

Anyone who has ever worn clothes knows that different fabrics have different breathability levels. Go for a hike up a mountain in the wrong garment & you'll feel like you're wearing a plastic bag with how sweaty you get - or like you've put clothes on straight from the washing machine.

This is where breathability ratings come in handy - as long as you can understand them.

Let's start with the rating types.

The Moisture Vapour Transmission (MVT) measurement is most commonly used, & indicates the amount of water vapour (ie: sweat) that can pass through one square metre of fabric in 24 hours. The water vapour is measured in grams - hence the grams per square metre per 24 hours rating usually displayed.

This could look like:

10,000g/m2/24H

10,000g

10,000gsm/day

This measurement uses either The Upright Cup Test or The Inverted Cup Test, both of which measure how much water vapour is pulled through fabric from the outside to the inside - either from the air (Upright) or a tub of water (Inverted).

MVT rating: the higher the number, the more breathable the fabric.

 
The Resistance to Evaporative Heat Transfer (RET) measurement is used by a smaller number of manufacturers, so it is not as commonly seen. This is measured using The Sweating Hot Plate Method (no, we're not joking). Water is placed onto a porous metal plate which is heated; as water vapour passes through the plate & the fabric, it causes evaporative heat loss & more energy is needed to keep the plate at the same constant temperature. This is then converted to a rating scale starting at 0 & rising to over 30. A RET score of 0-6 is considered very good - the fabric has a low resistance to moisture transfer, thus is more breathable.

This could look like:

Breathability | 5

Breathability | >6

RET 6

RET rating: the smaller the number, the more breathable the fabric.

Confused? At least we haven't gone into details of the second law of thermodynamics! 🤪

 
Thankfully, here at House of Uniforms, we aim to make it as easy as possible for you to choose the right garments for your business or yourself. Here's our quick guide to breathability:

 Want to learn more about breathable fabrics? Check out our guide to what makes a fabric breathable!

 
Or perhaps you'd like to know how Water Resistance Ratings work for that high breathability jacket you're considering?