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Breathable Fabric: More Space between Fibers Leads to Cooler Sleeping Experience

Breathable fabric is what makes a weighted blanket cool; we looked at the differences in fabrics to develop the truhugs weighted blanket.

Defining Breathable Fabric

If you were to take a microscope and hold it up to each thread, what would you see? Increased raw material porosity leads to an increase in breathable fabric (breathability is measured by air permeability). Each yarn thread consists of hundreds of little fibers shown below. Finding the perfect breathable fabric will improve the understanding of what materials will create an ideal weighted blanket.

Breathable fabric under a microscope; bamboo fibres shown
Visual images of regenerated bamboo porosity

If we define x as fabric density while including air between fibers (F1) divided by raw material fiber density (F2), the breathable fabric is defined as equal to “1 – x”.

So in F1, we are measuring the density of the fabric (how close each fiber is pushed towards the other in the pictures above).

For F2, we are determining the mass-volume relationship as the average density across all the solid fiber material itself. Thus, as x gets larger the porosity would decrease.

To maximize breathable fabric, we would want to minimize our ‘x’ numerator (F1, means big air pockets because most of the fabric is not the fiber material…which is heavier than air) while maintaining a decent denominator (F2, individual fibers density…fibers have to be made into yarn threads which are then woven into fabrics…so F2 is a pre-determined variable that always helps determine F1).

This means we want high-density raw material fibers that are high density in and of themselves. However, we don’t want them to be smushed together; that outcome would be the result of high fabric density, a low-density fabric would be super soft and smushy and airy.

The negative outcome of low porosity would be slow air movement as air is moving through the yarn threads themselves. Of course, air can also move around the yarn threads, which is affected by weaves and will be discussed later. An increase in porosity results in the fabric having higher air permeability aka ‘breathability,’ which will be appreciated by most people when they sleep.

fabric breathability
(Ozdemir, 2017)
I repeat “By increasing the yarn density, the dimensions of the pores become smaller, thus the permeability decreases.”

Porosity can be manipulated by changing a fabric’s thickness and density (fluffiness) ratio. Porosity is a major raw material factor that helps breathability, which allows sweat to escape instead of causing bacteria. To learn more about other raw materials lingo relevant to everything ‘fabric’, please read our article on the “measured thermal regulation outcomes of textiles.”


Ozdemir, H. (2017).  Permeability and wicking properties of modal and lyocell woven fabrics used for clothing. Journal of Engineered Fibers and Fabrics, 12(1), 12-21.


When my brother started truHugs, I was skeptical as to whether weighted blankets really worked. Using my research background in Kinesiology I quickly dove into the science to discover that weighted blankets, to my surprise, have some documented positive effects during use. Obsessed with product improvement, I promise to use my background in a diverse field of sciences to continually help improve our products for maximum comfort and benefit. I hold a M.S. in Kinesiology and M.B.A. along with 13 industry related certifications.

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