Is Polyester Warm? (Scientifically Explained) (2023)

Is Polyester Warm? (Scientifically Explained) (1)

Yes, polyester is warm because the woven fibers of polyester fabric trap the ‘still’ air between them.

And our science says that air is a poor conductor of heat and that’s why this trapped air acts as a thermal insulator so that the body doesn’t lose its heat in the surrounding environment due to temperature gradient.

But it doesn’t stop here because the amount of heat that polyester fabric will provide depends on several factors. However, the three most important factors are the yarn structure, fabric structure, and the thickness of polyester clothing.

Read Also: How Breathable Polyester Can Be? (Scientific Explanation)

Keep reading the article because now we’re going to share how warm the polyester is and why all the factors mentioned above matters if you want your polyester-made jackets or shirt warm.

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How warm is polyester? (Scientifically explained)

Technically, polyester-made clothing like a jacket can keep you warm enough in temperatures around 30 degrees Fahrenheit if it is tightly woven ripstop shell insulated with quilted polyester.

But there will be a significant loss in thermal insulation of polyester in wind chill. Because when the wind temperature drops and velocity increase the cold air that is now passing through the garment will replace the still air which acting as an insulating layer.

Now you need to understand something very crucial here. Polyester is a synthetic fabric that can be constructed either to keep you warm or cool.

Manufacturing wise, if polyester fabric is tightly woven and have a high thread count then it will keep you warm in winter while being quite breathable because it will increase the number of gaps between the fibers that are tiny in size which will hold the still air in multiple air pockets and at the same time have reduced air permeability.

On the other hand, if your polyester clothing is loose-fit or loosely woven, it means that it has larger size of pores which allow incredible breathability and high air permeability which make it a good choice for summer but not in winter.

Hakan said that the Cellular weave which is derived from satin and diced weave is a compound weave and shows the highest thermal resistance.

If you’re looking for a nonallergenic insulator then you should go for textured polyester to stay warm and that is the main reason why this is used for quilting, filling pillows, outerwear, and sleeping bag.s

According to research published on fabric made of microfiber shows lower heat conductance and therefore provides better thermal insulation than conventional polyester fabric.

FYI, microfibers are synthetic fibers that are typically made of polyester and they are very fine strands and very porous in nature.

That’s why because it contains more pores or gaps between the fibers, the microfiber polyester clothing can hold more still air pockets and thus provide more thermal insulation without blocking the breathability.

Please note that it is not the conductivity of fiber that tells the thermal properties of given textile instead it is the thermal resistance offer by the trapped pockets of air that reflect the body heat instead of letting it escape.

As in the introductory part, I’ve told that apart from the porosity the other major important factors are fabric thickness, weight, and density.

According to researchers, if you increase the thickness of polyester fabric the heat conductivity reduces and it takes more time for body heat to escape or the cold air and temperature variation to penetrate.

This further gets delayed because of the insulating layer created by the tiny pockets of trapped air.

Though, the major problem behind this is when you increase the thickness of fabric the breathability also gets compromised which is even getting more reduced as the porosity of the fabric is reduced.

That’s why another advancement came into play where it is found that if the thickness of two polyester fabrics is the same but the densities are tweaked we can see a substantial change in overall warming performance.

Proving the same thickness and weight, if the density is reduced the breathability and warming capabilities of polyester will also get reduced.

However, the woven microfilament polyester yarn with high density is shown to provide good thermal insulation in windy conditions because of reduced thermal conductance and transport the sweat vapor more easily than any other counterparts.

Frankly speaking, the above discussion can be too technical for common people so by taking the above account I am going to answer some general questions that you might have regarding the warmth of polyester.

Is 100 polyester warm?

Absolutely, the 100% polyester feels to be warm but the amount of warmth will depend on the fabric density, thickness, and the number of pores present between the fibers and yarn.

As the 100% polyester gets thicker, dense, and tightly woven it will provide more warmth because of reduced air permeability and increased numbers of small-sized pores which will hold the still air to make it act like an insulated barrier.

Is polyester warmer than cotton?

No, polyester is not warmer than 100% cotton but still, the polyester fabric is ideal to wear in winter because of its moisture-wicking characteristics and not losing the insulation even when getting wet.

Research is done by Colby, Marc, Nathan, and Nicholas clearly shows us that cotton insulates better than polyester.

Here’s what they did and observed…

They heated the water in an aluminum container and wrapped it up with polyester and cotton. And measured the water temperature every 5 minutes for a period of 30 minutes.

What they found is really fascinating.

Over 30 minutes, the water with no insulator dropped by 19.3 degrees Celcius. Using cotton as an insulator, the temperature dropped by 12.4 degrees Celcius.

And, with polyester as an insulator, the temperature of water dropped by 13.9 degrees Celcius.

Thus all the numbers are speaking blatantly that cotton is observed to be the most effective insulator than the polyester.

Is polyester warmer than wool?

Yes, polyester is warmer than wool because it demonstrates better insulating qualities than wool.

According to research when wool and polyester are used as an insulator by wrapping it up on heat water sitting in an aluminum container.

After testing the water temperature every 5 minutes for a 30 minute period.

It is observed that over this period when wool is used as an insulator the water temperature dropped by 19.2 degrees Celcius and on the other hand the polyester as insulator dropped the water temperature by 13.9 degrees Celcius on average.

Is polyester warm in summer?

Yes, polyester get’s warmer in summer but how hot it will get depends on the fabric construction. Like if it is tightly woven then it will get much hotter as compared to loosely woven polyester.

But because the polyester does not absorb sweat due to its water-resisting capabilities you’ll end up getting a lot of sweat.

So, in short, polyester get’s warmer in summer and that’s it is the ideal choice for winter and not the hot summer day.

Is polyester warmer than fleece?

It depends, if the fleece is made up of polyester fibers then it will obviously be warmer like polyester but it is made from natural fibers then it may not be warmer than the polyester fleeces.

Is polyester warm when wet?

Yes, because the polyester threads and fibers are waterproof and thus don’t absorb water or moisture which helps the polyester to remain warm because of not losing the insulating characteristics even when getting wet.

Is polyester warm to wear?

Yes, polyester is warm to wear but not because it is inherently warm but because it uses our body heat to maintain the temperature when the surrounding is cold.

This happens due to the presence of air pockets between the fiber where the still air is trapped.

And the trapped air act as a thermal insulating layer which reduces the thermal conductivity and reflects the body heat.

So if you’re a person who runs warm then you’ll remain warm in polyester clothing but if you run too hot then you may end up sweating when you’re wearing a tightly woven fabric which is considered much warmer because of reduced air permeability as the size of pores gets smaller and smaller.

Is polyester blanket warm?

Yes, polyester blankets are warm because polyester is a good thermal insulator but if you increase your budget then you must go for wool or cotton blankets because polyester is not much breathable when you expect it to be warm and don’t let the moisture escape which may end you up in a sweat.

And this sweat can make you cooler if it is a cold camping night or disgusting on a hot night.

Is polyester fill warm?

Yes, polyester fill clothing like jackets are warm in nature because the polyester fibers trap the still air which acts as an insulating barrier to keep you warm and toasty,

However, when it comes to filling, you need to know that the warmth of a particular will increase when you increase the fill weight of polyester fibers.

It plays many roles but the major is when increasing the volume of polyester fill the material generally gets puffier and the heat conductivity will decrease.

Is polyester viscose warm?

Yes, polyester is warmer than viscose because viscose can absorb moisture and water.

Is polyester warm for winter?

Yes, you can definitely consider polyester as winter wear because polyester will keep warm. But, remember if you want your polyester garment to be warmer then you should go with thick and dense tightly woven polyester fabric.

Is recycled polyester warm?

Yes, recycled polyester is warm because even if it is recycled the thermal insulating characteristics won’t change.

Because the recycled polyester will still contain porous fibers which will trap the air. And once the air is trapped it will act like an insulator which will get warmer using your body heat and in that process will keep you warmer.

Are polyester coats or jackets warm?

Yes, polyester coats and jackets are warm.

But if the coat is made of quilted polyester, the fabric is tightly woven, and if it contains microfibers then it will keep you much warmer than conventional polyester coats and jackets.

Are polyester puffer jackets warm?

Yes, polyester puffer jackets are warm and I would say the puffer jackets made of polyester tend to be much warmer than normal jackets.

Because the quilted design of puffer jackets will store the polyester fiber in its place and will make it act like an individual set of fibers that will insulate you much better.

A tip, as your polyester puffer jacket becomes puffier it will get warmer and warmer.

Are polyester gloves warm?

Yes, polyester jackets are generally warm but they can sometimes be cool so it is best that you use the polyester gloves as the outer shell and a lining made up of wool, etc, should be there to retain the warmth.

Finally, is polyester warmer than down?

No, polyester on its own is not warmer than down but it is also not as expensive and cruel as down.

Although, nowadays polyester is helping to make the technical fabrics like the Thermoball which is tested that it gives the warmth of 600 fill down and is a plus point it does not lose it’s insulation when getting wet as down does.

Read Also: How Warm Are Down Jackets In Reality?


So I hope you got your answer that, polyester is warm in nature because the polyester fibers have a large number of pores that trapped the air and as you know air is a poor conductor of heat thus it makes the polyester act as an insulating layer to get warmer using our body heat and keep us warm in that process.

Also, you saw that increasing the thickness, density, and reducing heat conductivity by adding layers of polyester fabric can hugely increase the warming potential of the polyester.

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Is Polyester Warm? (Scientifically Explained) (2)


Michael is heavily inclined towards traveling to natural places and documenting cultures/people from different parts of the world. He also loves hiking and camping and is spirited toward all outdoor activities. He will share his passion for outdoor life and brands or products we use outside our homes. He has good research skills, and that’s why you can see why his articles are packed with info that is factual and not readily available. He also has the vision to travel the whole world and share it with all readers of Outdoor Favor.


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