Do you really lose your body heat through your head? Winter myths and facts

“Put your hat on, you lose half your body heat through your head!” Everyone has heard it, usually from a grandmother at the front door. The advice is good, but the figure is wrong. Here is what we actually know about how the body loses heat in winter, and what it means when choosing a beanie, a scarf and gloves.

Where the “50%” myth comes from

The figure long appeared in a US Army survival manual, which spoke of 40 to 45% of body heat being lost through the head. It is thought to date back to military experiments in the 1950s: volunteers were exposed to the cold in insulated suits… but bareheaded. Unsurprisingly, most of the heat escaped through the only uncovered part.

In 2008, two doctors revisited the question in the British Medical Journal: the head accounts for roughly 7 to 10% of the body's surface, and it loses about the same proportion of heat. In other words, the body loses heat wherever it is uncovered, roughly in proportion to the exposed surface. Go out in a T-shirt and a beanie, and it's your arms that will feel the cold.

So why does your head feel cold so quickly?

Because the face, scalp and neck are among the areas most sensitive to temperature changes. In winter, they are also often the only parts left uncovered while the rest of the body is wrapped up in a coat. You feel the cold there first, and a beanie brings immediate, very noticeable comfort. Grandma's advice still stands, just for a different reason.

Where heat really escapes

Hands, the first to be sacrificed

In the cold, the body protects its vital organs first: it reduces blood flow to the extremities. Fingers therefore cool down much faster than the rest, even under a good coat. That's why gloves matter as much as a beanie. We've gathered our best advice in 7 tips to keep your hands warm.

The neck, the forgotten zone

Between the coat collar and the beanie, the neck is often left exposed to the wind. A well-tied scarf closes this “chimney” through which cold air gets in and warm air escapes. To tie it with style, see our 5 ways to tie the KANDER scarf.

Moisture and wind

A damp material conducts heat away far faster than a dry one, and wind strips away the thin layer of warm air around the skin. Staying dry and sheltered from the wind often matters more than the thickness of your layers.

Winter: true or false

• “You lose half your heat through your head.” False. About 7 to 10%, like other uncovered areas of similar size.
• “So a beanie is useless.” False. When the rest of the body is covered, the head is one of the last exposed areas: covering it really changes how cold you feel.
• “Cold hands mean the body is protecting itself.” True. Blood is redirected to the core, and the extremities cool down first.
• “The thicker, the warmer.” Not necessarily. What insulates is still air trapped in the fibre, and a material that makes you sweat ends up chilling you.
• “Damp wool no longer keeps you warm.” Partly true: any wet material insulates less. Hence the value of a fibre that breathes and dries quickly.

Where alpaca makes the difference

Alpaca fibre is partly hollow: it traps still air, which lets it insulate a great deal for very little weight. It also lets water vapour through instead of holding it in, avoiding the “cold compress” effect after exertion. We explain it in detail in Why alpaca keeps you warm without making you sweat.

In practice, the most effective trio covers the three areas that cool fastest: a beanie such as the ÄGERI beanie or the SARNEN beanie, the KANDER scarf around the neck, and the touchscreen-friendly TITLIS gloves for your hands. All three come in matching gift sets, as easy to give as to keep.