What Is Warmth-to-Weight and Why Does It Matter in a Winter Hat?
Share
The short answer: warmth-to-weight is how much insulation a fabric gives you for every ounce it weighs. The higher it is, the warmer a hat can be without getting heavier or bulkier. It matters in a winter hat because weight and bulk are exactly what make a warm hat uncomfortable enough to take off.
Most of us have owned the other kind of hat. The thick wool one from the bottom of the drawer. It was warm, sure. It was also heavy, itchy after an hour, damp by the end of the day and still damp the next morning. You wore it when you had to and left it on the hook when you did not.
That hat had plenty of warmth. What it did not have was warmth-to-weight.
What warmth-to-weight actually measures
Warmth-to-weight compares two numbers:
-
Thermal resistance: how well a fabric slows heat escaping from your body. In a lab this is measured on a heated plate that works like artificial skin. The fabric is laid over the plate, and testers measure how much energy it takes to keep the plate at body temperature. The less energy needed, the better the fabric insulates. Results are usually expressed in units called clo or tog.
-
Weight: usually measured as weight per area, in grams per square meter or ounces per square yard.
Divide the first number by the second and you have warmth-to-weight: insulation per ounce. It lets you compare a thin, light fabric with a thick, heavy one on equal terms.
Why weight matters more on your head than anywhere else
A few extra ounces in a jacket spread out across your shoulders. A few extra ounces in a hat sit in one spot, on top of your head, all day long. Heavier hats tend to be less comfortable over time. They press down and tend to be bulkier, which traps heat and sweat in a very small space.
This creates the pattern most winter hat wearers know well: warm, then too warm, then damp, then cold, then off. If you have ever tried to make a full swing in a heavy knit hat, you know how quickly bulk gets in the way, which is something we covered in our guide to cold weather golf.
A hat with high warmth-to-weight gives you the insulation you need without the weight that makes you want to take it off. The warmest hat is the one you keep on.
How common winter hat fabrics compare
In warmth-per-weight testing of the Polartec fabric used in the Original Howley, Polartec Classic delivered roughly twice the warmth-to-weight of merino wool and four times that of cotton. You can see the full chart on our High Performance Metrics page.
|
Fabric |
Warmth per ounce |
When it gets wet |
Drying time |
Best for |
|
Cotton |
Lowest of the three |
Absorbs water and loses most of its insulation |
Slow |
Mild, dry days only |
|
Merino wool |
About 2x cotton |
Absorbs moisture vapor and can still feel dry, but gets heavy when soaked |
Moderate |
Everyday wear, indoor-outdoor, a wide temperature range |
|
Polartec fleece |
About 2x merino and 4x cotton |
Absorbs very little water and keeps insulating |
Fast |
Deep cold, active use, changeable weather |
What about acrylic? Many inexpensive beanies are acrylic knits. Their performance varies a lot depending on how they are knit, and looser knits let the wind straight through.
Why Polartec fleece scores so high
Polartec fleece traces back to the early 1980s, when Malden Mills in Massachusetts developed it as a lighter, quicker-drying alternative to wool. The fabric is knit and then brushed into a raised pile, a dense forest of fine loops that holds a large volume of still air for very little material.
Because its fibers take on very little water, the fabric keeps insulating when you sweat and dries quickly. That mix of low weight, high warmth and fast drying is a big part of why TIME magazine recognized Polartec as one of the most important inventions of the 20th century.
When our founder bought his first Polartec hat from some Vermonters at a country store in the late 1980s, the fabric still felt like astronaut material. Forty years later, the Original Howley is made from genuine Polartec fabric milled in New Hampshire and Tennessee, then cut and sewn in New Jersey. You can read the whole story of how Howley got started.
Where merino wool still earns its place
High warmth-to-weight is not the only thing that makes a hat great, and we would be the last people to tell you wool is obsolete. We make two merino wool blend hats for good reason.
Merino is soft against your skin, naturally resists odor and stays comfortable across a wide range of temperatures, which makes it excellent for hats you wear in and out all day. The House Hat is a lightweight merino wool blend beanie made for real life, starting indoors, and it folds small enough to fit in your jeans. The Low-G House Hat Skullcap is a low-profile merino wool blend skullcap that layers neatly under helmets and hoods.
The simple rule: choose Polartec when warmth for its weight is the priority, and choose merino when everyday softness and versatility matter most. In fact, we feel the two hats compliment each other well, so why not treat yourself to both?
Warmth-to-weight is not the whole story
A fabric with brilliant warmth-to-weight can still make a disappointing hat. Three other things decide whether you actually stay comfortable:
-
Fit. Howleys always utilize materials that contain stretch, but stretch alone doesn’t always make for an optimized fit. The Original Howley comes in five true sizes, XS to XL, so it holds warmth in without squeezing.
-
Breathability. A warm hat that traps sweat will eventually make you cold. Polartec breathes and moves moisture away from your skin.
-
Wind and weather. A brim helps a lot. The Boss Howley pairs the same Polartec warmth with a patent-pending brim, and you can learn more in Meet the Howley Brimmed Hats.
We explain how all of these work together in The Science of Comfort: Engineering the Best Cold Weather Gear.
How to use warmth-to-weight when you shop for a winter hat
Most hat brands do not publish warmth-to-weight figures, so you often have to read between the lines. These questions will get you most of the way there:
-
What is the fabric? Look for a named performance fleece like Polartec or a quality merino, rather than a vague "soft knit."
-
How bulky is it for how warm it claims to be? Thick is not the same thing as warm.
-
What happens when it gets wet? Cotton and loose knits lose their warmth fast.
-
Does it come in sizes? A light hat that fits beats a heavy hat that gaps.
-
Is it built to last? High performance is not worth much if the hat pills and stretches out in one season. The Original Howley is backed by our Lifetime Guarantee.
Frequently asked questions
What is warmth-to-weight ratio?
Warmth-to-weight ratio is the amount of insulation a fabric provides for every unit of weight. A higher ratio means more warmth without extra weight or bulk.
How is warmth-to-weight measured?
A fabric's thermal resistance is measured on a heated plate that simulates skin, then divided by the fabric's weight per area. The result shows how much insulation you get per ounce or per gram.
Is fleece warmer than wool for its weight?
Yes. In warmth-per-weight testing of the Polartec fabric used in the Original Howley, Polartec Classic delivered roughly twice the warmth-to-weight of merino wool and four times that of cotton.
What is the warmest lightweight material for a winter hat?
Performance fleece such as Polartec is one of the warmest materials for its weight. It also keeps insulating when damp and dries quickly.
Does a heavier winter hat keep you warmer?
Not necessarily. Warmth comes from trapped still air, not from weight. A heavy, dense hat can hold sweat and end up leaving you colder than a lighter hat with high warmth-to-weight.
Why does Howley use both Polartec and merino wool?
Polartec gives the most warmth for its weight, which is ideal for deep cold. Merino wool blends are soft, odor resistant and comfortable across a wide temperature range, which is ideal for everyday and indoor-outdoor wear.
Twice the warmth, half the weight, five real sizes. Bring on the cold with the Original Howley.