The Innergy Bar is the thermal-storage heating module at the core of the system: a heat pipe, a self-regulating heater, elvan stone and an aluminium storage tube combined into one unit. It measures 1,650 × 70 × 44 mm, weighs 4 kg, and runs at 220 V / 100 W. The heater vaporises the nano fluid inside the heat pipe, which rapidly heats the elvan stone, and the stored heat is then released as far-infrared radiant heat.
A heat pipe moves heat by phase change rather than conduction, which gives it an effective thermal conductivity of roughly 10,000 to 100,000 W/m·K — about 25 to 250 times that of copper. Inside an evacuated tube sits a working fluid with a low boiling point; because the pressure is reduced, the self-regulating heater at one end vaporises it easily, and the vapour travels the length of the pipe carrying latent heat with it. As the heat dissipates the vapour condenses back to liquid and returns to its starting position. That phase change repeats indefinitely, so circulation is fast, stable and self-driven with no external pump.
It is a heating element that controls its own temperature: once the set point is reached it reduces its own current to hold that temperature. It draws only the power the heat load actually needs, which minimises waste, and because it cannot reach a runaway overheat state there is no fire or burn risk. It produces no EMF, no noise and no odour, and because the module is a bolted assembly, a failed part can be swapped by someone who is not a specialist.
Elvan stone emits far-infrared radiant heat, which reproduces the feel of a traditional gudeul floor. Its thermal-storage performance keeps the warmth going well after the power is off, delivering the snug heat of the traditional warm spot. Because it does not heat the air directly there is no oxygen depletion, dry eyes or respiratory irritation. It is a natural material that neither deforms nor corrodes, giving a service life of 30 years or more and posing no disposal concern.
Per KIFA test report KFI-127, emissivity is 0.924 out of 1.0. Radiant energy is 4.28 × 10² W/m²·µm at 50 °C, and the measured band is 5–20 µm, which is the range the human body absorbs best. The figure was measured at 50 °C — a real operating condition for a floor in use, not a laboratory-only setup.
On electrical efficiency alone the heat pump wins: COP 3.0–4.5 against Innergy Ondol's COP 1.0, which converts electricity to heat at 100%. The difference shows up in operating conditions. A heat pump's efficiency falls sharply below freezing, defrost cycles interrupt heating, and the outdoor unit carries a freeze risk. Innergy Ondol holds COP 1.0 regardless of outdoor temperature and has no outdoor unit and no defrost cycle. The heat pump does both heating and cooling; Innergy Ondol is heating only. Installed cost is KRW 12–15 million and up for a heat pump plus dedicated plant space, against KRW 400,000–1,000,000 per pyeong (3.3 m²) here.
In KETI testing from a −15 °C start, the Innergy Bar reached a surface temperature of 31.1 °C just 31 minutes after power-on, drawing 70.65 W/h. It also operated from −40 °C, reaching an average surface temperature of 32.2 °C after 126 minutes at an average 88.0 W/h. Rated power is 100 W.
Think of it as a conventional system turned inside out. Hydronic radiant floor heating puts a boiler outside the room, heats hundreds of litres of water, and pumps it through pipes buried under your floor — the water is the transport, and the volume is what makes a leak a renovation. Innergy Ondol puts the boiler inside the element. Each heat pipe holds a few millilitres of water sealed under vacuum; a heater at one end boils it, the vapour carries heat the length of the bar, it condenses and returns. Same physics of moving heat with water and steam, at a thousandth of the scale, with no pump, no boiler room and nothing plumbed.
Three. The EPP method is DIY-capable self-installation, suited to smaller spaces. The ALC block or multi-board method suits large floor areas and is recommended for professional installation. The floor-grooving method is used for remodels and retrofits.
The EPP block method is designed to be assembled and installed without professional labour and is recommended as the DIY material set. The sequence is: prepare a clean floor; lay Innergy blocks over the heated area; fill the unheated remainder with pink foam; install the Innergy Bars and connect the harness wiring; attach the heat-diffusion plate and finish with aluminium tape; cover the whole surface with 12T plywood. Finish flooring is separate. Note the step that connects 220 V wiring — if you are not comfortable with electrical work, use a professional installer.
Innergy block 900 × 900 × 60 / 2.5 kg; 12T EO plywood 1,220 × 2,440 × 12 / 20 kg; unheated block (pink foam) 900 × 1,800 × 60 / 3 kg; Innergy Bar 1,650 × 70 × 44 / 4 kg / 220 V 100 W; thermostat plus harness wiring 120 × 120 × 34 / UTH-300; heat-diffusion plate 900 × 900 × 0.6. The thermostat may be substituted with an equivalent or better model depending on site conditions.
ALC block or multi-board 600 × 600 × 100; volcanic stone board 1,200 × 2,400 × 12; Innergy Bar 1,650 × 70 × 44 / 4 kg / 220 V 100 W; thermostat plus harness wiring 120 × 120 × 34 / UTH-300; heat-diffusion plate 900 × 900 × 0.6. The sequence is: prepare a clean floor; lay ALC block or multi-board; cut grooves for the Innergy Bars; install the bars and connect the wiring; attach the heat-diffusion plate; lay the volcanic stone board and finish. It makes levelling a large space easier, allows bar spacing to be tuned to the climate, and can reuse an existing screed structure.
Standard installed height is 73 mm. The final height varies with the material and thickness of the finish flooring, and levelling can move it by roughly 82 mm ± 5 mm. In a multi-storey building, inter-floor acoustic material may be added on top.
Yes. It is demountable and can be laid over an existing floor without demolishing the building structure or tearing out the slab. Remodels and retrofits use the floor-grooving method. Because installation is pure assembly, it deploys quickly on both new-build and renovation sites.
Yes. Two thermostats, left and right, set temperature by zone. Even within one room you can split into two zones — a sleeping area at 40 °C and a living area at 30 °C — and adjust by season and weather. Innergy Bars are simply not laid under furniture or anywhere no one walks, so no energy is spent there. With a single boiler serving several rooms, per-room setpoints are effectively impossible.
Not directly. Nest and most smart thermostats are 24 V low-voltage controllers — they signal a separate appliance such as a furnace or heat pump. Innergy Ondol switches 220 V straight to the heating element, so there is no 24 V control circuit for one to connect to. Electrically it can be done with a contactor in between, which lets a low-voltage thermostat open and close the circuit. We do not recommend it, for three reasons. It senses the wrong thing: a wall thermostat reads air temperature, while floor heating is regulated on floor surface temperature, which is what the supplied thermostat's floor sensor reads. It loses zoning: a contactor is a simple switch, so the two-zone control that lets one room run 40 C for sleeping and 30 C for living is gone. And it puts the installation outside the product's certified configuration, which is where certification and warranty coverage end. The supplied thermostat (UTH-300, 120 x 120 x 34 mm) reads the floor and controls two zones. Remote control is not part of the product today.
Innergy Ondol uses a self-regulating heater that reduces its own current once it reaches the set temperature. Because the structure cannot run away to a high overheat state, the usual causes of fire and burn injury are removed rather than managed. Film and resistance-wire systems place the heating element close to the finish material, so unbalanced current distribution can lead to fire or a burn; that structural cause is designed out here. If a product has actually smoked, sparked, or burned someone, do not rely on this answer — ask to be connected to a person straight away.
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The architecture genuinely differs from film or cable heating. Current reaches only the self-regulating heater at one end of the bar; the heat pipe carries heat, not electricity, so no current flows across the floor area the way it does in a heating film or a resistance cable. That is where the magnetic-field reduction comes from, and it is a structural property rather than a shielding layer. The heater itself is also silent and odourless. For a measured figure, ask for the KTC test report — electromagnetic results are on page 6.
There is no boiler and no plumbing. The only water in the system is a few millilitres sealed inside each heat pipe under vacuum, where it boils at low pressure, carries heat along the tube, condenses and returns to where it started. It never circulates, never leaves the sealed tube, and there is no run of pipe to freeze or burst. In wet hydronic heating a burst pipe means tearing out the whole floor; here there is no circulating water for that to happen to.
Yes. In accredited testing (KCL), a 500 kg test tank load produced no cracking and held 0 mm of level difference. Carbon-fibre heating film, by contrast, breaks its conductor under compression, which becomes a cause of fire and failure. That said, it is more energy-efficient not to run Innergy Bars under furniture where no one walks.
Yes. In accredited testing the carbon system had to be capped at 12 hours because continuous operation carries an overheat risk, while Innergy Ondol was tested with no such time limit. The self-regulating heater cuts power at the set temperature, so continuous running does not accumulate heat.
On the Korean residential low-voltage tariff, estimated for an identical 4,000 × 4,500 mm space: Innergy Ondol draws 660 kWh a month at roughly KRW 200,000, against 1,080 kWh and roughly KRW 350,000 for carbon-fibre film. Annually that is about KRW 2.4 million against KRW 4 million — a KRW 1.6 million difference while running 2 °C warmer. Under progressive tariff bands the monthly gap can more than double. Your actual bill depends on area, insulation, habits and tariff, so a precise figure comes with a quote.
It is a measured case from a 26-pyeong (86 m² / 925 sq ft) house in Hajinbu-ri, Jinbu-myeon, Pyeongchang-gun, Gangwon-do, built November 2023. Even in the December 2025 cold snap with temperatures down to −20 °C, the billed amount was KRW 13,210, evidenced by the utility statement. The conditions: 52 Innergy Bars (5.2 kW) in an all-electric house where hot water, cooking and appliances are also electric, with 6 kW of solar and net metering. December usage was 200 kWh household plus 251 kWh heating; spring and autumn export credits brought heating to zero and the bill to KRW 13,210. Without solar, the highest monthly bill was KRW 231,100 in February 2024.
KRW 400,000–1,000,000 per pyeong (3.3 m² / 35.6 sq ft), varying by region and application. Because it depends on area, method (EPP, ALC or floor-grooving), finish material and site conditions, a precise figure comes from a quote once we have the site details. For a small house there is also roughly KRW 10 million saved in construction cost by not needing a boiler room.
At roughly KRW 2.5 million saved in fuel each year, payback on the initial installation is estimated at under about five years. Worth weighing alongside that: no oil or gas refilling, and because there is no circulating water and no plumbing, no freeze risk and almost no maintenance.
Put a well-insulated building, Innergy Ondol and renewable generation together and the loop closes: energy produced during the day is stored in the floor and released when it is needed. The elvan-stone storage module acts as a thermal battery. In the Pyeongchang case, 6 kW of solar with net metering brought the heating bill to zero. This pairing is the core of the zero-heating-bill claim.
It suits that use well. There is no circulating water and no plumbing, so nothing can freeze and burst in an empty house, and there is no outdoor unit, so no defrost cycle and no freeze risk there either. It holds COP 1.0 regardless of outdoor temperature, so performance does not fall away as it gets colder. In KETI testing from a -15 C start the Innergy Bar reached 31.1 C after 31 minutes, and from -40 C it reached 32.2 C after 126 minutes. The 26-pyeong house in Pyeongchang, Gangwon-do was billed KRW 13,210 through the December 2025 cold snap that fell to -20 C. One recommendation: hold it at a low temperature rather than switching it off entirely. Thermal storage cuts both ways — once warm it stays warm for a long time, but a house that has gone fully cold takes a while to bring back. Accredited testing showed 76 minutes to lift an 8 m2 chamber from 18 C to 22 C, and warming a whole empty house from below freezing is a matter of hours rather than minutes. Holding a low floor turns that into a short lift before you arrive. The right holding temperature depends on the house, so we work it out with you. Worth knowing: remote control is not part of the product today. The UTH-300 thermostat is a wall unit.
Hinoki Gudeul is an all-in-one finished platform with the Innergy Bar built in, and has been Ondol Life's flagship item since 2008. Given an electrical supply it installs and runs immediately. It is built from hinoki louvre boards that release phytoncide, elvan stone for thermal storage, a heat pipe playing the role of the traditional flue, a PTC heater playing the role of the firebox, and a heat-diffusion plate that spreads the heat evenly across the surface. Two sizes: Hinoki Gudeul 1000 at 1,000 × 2,000 × 67 / 300 W, and Hinoki Gudeul 800 at 800 × 2,000 × 67 / 200 W, supplied with a 500 × 1,000 × 20 carbonised cork board and a UTH-300 thermostat and harness.
Yes, particularly rest areas in facilities that run around the clock — power plants, fire stations, police stations. It delivers steady radiant warmth silently, with no fan and no pump, which suits a space meant for rest between shifts. Surfaces are raw timber with no paint or chemical finishes. It fits any space needing heat: village halls, senior centres, care classrooms, residential facilities for disabled people, and regional children's centres.
In a country house installed January 2019, a two-person household running a 26-pyeong, 2.4 kW Hinoki Gudeul averaged 349 kWh a month across the eleven months from August 2020 to June 2021 — peaking at 832 kWh in January and bottoming at 239 kWh in June. Those figures are total household electricity including heating, hot water, cooking and appliances. It is now in its seventh year of verification, with total annual household energy cost under KRW 300,000 when paired with 6 kW of solar.
The module is a bolted assembly, so a failed part can be swapped module by module without a specialist. Defects are addressed at module level, which keeps maintenance simple and the maintenance budget down. The heat-pipe approach has no mechanical wear, so durability is long, and where impact damage does require service, the electronic parts — heater, thermostat — are designed to be replaced as components. Compare film heating, where a creased sheet can be neither spot-repaired nor relocated.
Elvan stone is a natural material that neither deforms nor corrodes, giving a service life of 30 years or more with no disposal concern. The structure as a whole is semi-permanent at 30-plus years of durability, which is where the maintenance saving comes from.
Yes — an inspection port is built in during installation, and the wiring section must be closed with screws rather than fixed shut, so that later service is straightforward. The sequence is: prepare a clean floor; lay carbonised cork board; install the Hinoki Gudeul units and wiring; frame timber to set the height; lay plywood and fit the inspection port; finish with hinoki louvre and skirting.
Not yet, and the reason is certification rather than shipping. Innergy Ondol holds KC (Korea), CE (Europe) and PSE (Japan) approval. It does not currently carry a UL, ETL or cUL listing from a US Nationally Recognized Testing Laboratory, and a building-integrated electric heating system without an NRTL listing mark will not pass US electrical inspection — which in turn affects permitting and insurance, however well the product performs. A US-market version is part of the planned US factory programme. Let me connect you to someone who can tell you where that stands and take your details.
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The Innergy Bar is rated 220 V, 100 W, and KETI tested it at AC 220 V / 60 Hz. Frequency is not an obstacle in North America — Korea and the US both run 60 Hz, unlike Europe at 50 Hz. Voltage is closer than it looks too, since this is hardwired rather than plug-in and US homes carry 240 V split-phase circuits for exactly this class of load. What is not settled is whether the UTH-300 thermostat and the control electronics are rated for that supply, and that is an engineering sign-off rather than a question a catalogue can answer. The part that genuinely blocks a US installation today is the missing NRTL listing, not the volts.
Every order ships from the Korea warehouse today — it is the only fulfilment point currently operating, and it stocks the Korean electrical specification. A US factory and dropship operation is planned, and that is what will make a US-market product available; until it exists there is no second origin to choose between. For delivery outside Korea, let me connect you to someone who can confirm what is possible for your location.
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The first KC certification in the heat-pipe heating category, plus CE (Europe), PSE, ISO 9001 and INNO-BIZ certification. It received the Minister of Environment's Award in the eco-friendly energy category and the KIPO Commissioner's Award at the Korea Invention Exhibition in 2018, and is registered on the SME Technology Marketplace. There are more than ten patents; registered titles include a floor heating structure with an embedded heat pipe (1026639100000), a body-contact heater using a heat pipe, a far-infrared radiator, and a far-infrared hinoki heated bed.
Innergy Ondol was designated a 2026 Innovative Product by Korea's Ministry of Trade, Industry and Energy. Certificate number 2026-172, product title "gas-heated thermal-storage electric heating board with an embedded vacuum heat pipe", designated 26 June 2026 through 25 June 2029. The designation is made under Article 33(1) of the Enforcement Decree of the Procurement Business Act and Article 11(1) of the Regulations on Innovative Product Designation and Purchase Promotion, and makes the product a priority purchase target in public procurement.
Installed cost for Innergy Ondol depends on area, insulation, installation method, finish material and site conditions, so we quote once we have the site details. Let me connect you to someone who can take those. Hinoki Gudeul is a finished product in fixed sizes, so you can see it directly on the product page.
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