We didn't invent far-infrared warmth. Sunlight did. Kozy connects Korea's ondol tradition to a sense your body has carried all along — it already knows what to do.
A dog curling into the one patch of afternoon sun. The heavy, delicious drowsiness that finds you on warm sand. That isn't just pleasant. It's biology.
Far infrared is the warmth wavelength of sunlight — the light with the UV taken out and only the warmth left in. And here is the quietly remarkable part: it is the same wavelength your own body radiates.
So when you lie down on Litual, or close Poom around your back, you are not lying on a machine. You are receiving a signal your body has trusted for millions of years: the day is over now. You can put it all down.
For a decade the rules have been handed down: cold room, strict routine. The logic isn't wrong — your core temperature needs to drop for deep sleep. But shivering under a cold duvet spikes adrenaline. So you lie there: tense, cold, and wide awake.
What actually lowers core temperature is a warm microclimate. Gentle far-infrared warmth along your back dilates blood vessels. As they widen, heat flows out of your core toward your hands and feet — and your core temperature drifts down on its own. Not forced. Physiology, doing what it was built to do.
This is the ondol principle in one image: cool air at your nose, deep steady warmth at your back. Your body has always known what to do next.
An electric blanket toasts the surface: hot skin, tense body. Far infrared does what sunlight does — sends invisible waves past the skin, down to where the tension actually lives.
4 cm reach · 89.9% far-infrared emissivity · 24V DC, EMF-free · full power for the first 30–60 minutes, then under 1 watt · CE · UKCA · OEKO-TEX®
Deep warmth is one of the body's oldest safety signals. The alarm chemistry of the day quiets; the rest-and-recover state takes over. No meditation app required.
Dilated vessels mean better blood flow. Oxygen and nutrients reach worked muscles, easing out the tension the day left behind — while you sleep through all of it.
No app. No sleep score. No routine to keep. One button, and then the only job you have is the one your body was built for.
Warmth from below comes from ondol — Korea's underfloor heating, in continuous use since around 900 BC. Fire warms channels of stone and earth beneath the floor; the floor holds the warmth and gives it back, slowly, to the bodies resting on it. Nothing like Western heating, which blows hot air at the room.
When we first showed Litual at Station F in Paris, most people had never heard the word ondol. No one needed the explanation. They lay down, went quiet, and recognized it — not as new technology, but as a feeling they had somehow forgotten.
This isn't heat. Heat clings. Warmth holds.
Where the heat begins — a fire tended below the kitchen. The people resting above never even see it.
Invisible passages under the stone, carrying warmth quietly along their length. This is the blueprint for Litual's far-infrared yarn.
Stones that drink in the heat and radiate it upward — even, deep, and patient, wrapping the body from below.
Spent heat leaves, and the cycle completes. Warmth is never wasted here. It only moves on.
A 900 BC heat channel became the blueprint for a 21st-century thread. Every night, those threads carry warmth quietly beneath you — the newest version of a very old kindness.
A far-infrared warming layer that lies under the fitted sheet and warms the body, not the room — named after ondol, Korea's warmed floor. Cool air above, steady warmth below: the arrangement Koreans have slept in for three thousand years, brought to any bed. Unlike an electric blanket it has no coil heating the surface; far-infrared yarn sends warmth about 4 cm into the body, and it switches itself off. Litual is the ondol topper Kozy makes in Seoul.
Far infrared is the part of sunlight that carries warmth but no visible light and no UV — the wavelength band from roughly 3 to 1,000 micrometres, just beyond red. The human body radiates in the same band, which is why far-infrared warmth feels familiar rather than like a machine. Kozy's fabrics emit far infrared at 89.9% emissivity, and that warmth reaches up to 4 cm beneath the skin.
Ondol (온돌) is Korea's traditional underfloor heating, in continuous use since around 900 BC. A fire in the agungi (fire mouth) sends heat through gorae (channels) under gudeul (flat stones), which hold the warmth and give it back slowly to the bodies resting on the floor; spent heat leaves through the gulduk (chimney). Litual's far-infrared yarn is modelled on the gorae: warmth from below, held and released slowly.
A cool room is right; a cold body is not. Core temperature does need to fall for deep sleep, but shivering under a cold duvet raises adrenaline and keeps you awake. Gentle warmth along the back dilates blood vessels, heat flows from the core to the hands and feet, and core temperature drifts down on its own — the vasodilation paradox. Cool air at the nose, warmth at the back, is the combination the body is built for.
Up to about 4 cm beneath the skin — into muscle, blood vessels and nerve endings. Surface heat from an electric blanket stops at the skin, around 2 mm, which is why it feels hot rather than warm.
Your body already knows how to fall asleep. It doesn't need an app, a supplement, or a new routine. It needs one signal: you're safe now.
100 nights on Litual · 30 days on Poom · 2-year warranty · Made in Seoul