How to Use a Korean Boiler (Ondol): Every Button on the Panel, Explained, and Why Korean Floors Mean Shoes Off

Last updated: 21 October 2026. Boiler guidance here comes from Korean-language sources: Seoul Metropolitan Government's winter heating page, Korea District Heating Corporation advice reported in December 2025, Kyungdong Navien, Rinnai and Kiturami statements in the Korean press, and Navien's own app listing for the panel modes. The gas rate is from Seoul's public-tariff page (effective 1 September 2026) and the energy-voucher figures from Seoul's 2026 notice. Each is named in the Sources section.

A Korean boiler is the first appliance most foreigners in Korea get wrong. You move into a one-room, an officetel or a villa in November, find a small panel on the living-room wall marked 실내, 온돌, 외출 and 예약, turn the number up to 25 because you are cold, and the floor stays cold all night. Or you set it to 50 thinking that must be scalding, and it is just a warm floor.

The panel is not badly designed. It is designed for a heating system most of the world does not use: hot water running through pipes under the floor, the modern version of ondol (온돌), Korea's centuries-old heated floor. Once you know that, the buttons make sense, and so does the rest of Korean home life: why shoes come off at the door, why people sit and sleep on the floor, and why the family upstairs can be heard through it.

This guide does both halves. First the practical one: every button on a Korean boiler controller, which mode suits your flat, what to do when you leave for a weekend, and roughly what the gas costs. Then the culture behind it: ondol, shoes, slippers, low tables and the legal noise limits that come with living on the floor.

The 온돌 dial shows water temperature, not the room: TempPro TP50 room thermometer and humidity gauge on AmazonAffiliate link. As an Amazon Associate, EpicKor earns from qualifying purchases at no extra cost to you.

Quick Guide: The Korean Boiler and Floor, As of October 2026

Every Button on a Korean Boiler Panel

Almost every Korean apartment, villa, officetel and long-stay rental with its own gas boiler has a wall controller (실내온도조절기) near the living room, usually made by Kyungdong Navien (경동나비엔), Kiturami (귀뚜라미) or Rinnai (린나이). The layouts differ, but the core functions are the same: Navien's own app lists its boiler modes as 실내난방, 온돌난방, 온수전용, 외출, 난방 반복예약 and 난방 24시간 예약, and Kiturami describes its Wi-Fi controllers as having heating, ondol, timer, hot water and away as their basic functions.

The single most important thing to know is that the same number means two different things depending on the mode.

실내난방: the number is the air

In room mode the boiler behaves like a Western thermostat. Navien put it simply to Segye Ilbo in December 2025: set 23°C, go out, and when the room falls to 22°C the boiler fires until it is back at 23°C, then stops. The sensor is inside the panel itself, so the panel's position matters. Something hanging in front of it, a radiator or electric heater next to it, or afternoon sun on it will all make it read warmer than the room, and the boiler will stop early.

What to set: Seoul Metropolitan Government's winter guidance is 20°C, and it says each degree above 20°C can add more than 15% to heating costs, while setting 19°C instead of 20°C saves about 7% of the energy. Kiturami's January 2026 winter guidance gives 18–21°C. Older trade-press guidance (Gas News, 2021) said 20–22°C. If you are cold at 20°C, check the floor before the number: a cold floor usually means the mode is wrong, not the setting.

온돌난방: the number is the water

In ondol mode the panel ignores the air. It heats the water in the floor pipes to the number shown and keeps it there. So 50 does not mean a 50°C room. It means 50°C water under your feet, which is a warm floor, not a hot one. The winter range quoted in Korean guidance is 40–50°C.

This is the mistake foreigners make most often. Someone who sets an ondol panel to 22, thinking it is a room temperature, gets water barely above body-cool and a floor that never warms. Someone who reads 50 on a host's panel and turns it down to 25 does the same.

외출: away, not off

외출 holds the boiler at a low standby while you are away; it leans on the separate freeze protection described below and does not keep the flat comfortable. That is why Seoul's advice is specific: do not use 외출 when you are just going out for the day; set the heating 2–3°C lower than usual instead, and use 외출 only if you will be away for three days or more. Korea District Heating Corporation gave the same three-day line for district-heated flats in December 2025.

The reason is the floor itself. A concrete slab with water pipes is slow to warm. Letting it go cold for a nine-hour workday and then reheating it from scratch can use more gas than holding it a few degrees lower.

예약: the timer

Timer modes vary more than anything else on the panel. Navien's app offers both a repeat timer (반복예약) and a 24-hour schedule (24시간 예약). Older panels often have a single 예약 button that runs the heating on a repeating interval. Korean press guidance suggests a timer in draughty homes where room mode never reaches its target, for example running the floor every two to three hours. The exact intervals depend on the model, so look for the model number on the panel and the manual on the maker's site if the host cannot tell you.

Leave the power on

Every maker's winter advice includes this. Kiturami says its boilers have a two-stage freeze protection: when the heating water drops to 8°C the circulation pump starts, and at 5°C the burner fires. That protection does not work if the power is cut. In a cold snap, Kiturami says, keep the boiler plugged in and the gas valve and the floor manifold valves (분배기 밸브) open. A frozen boiler or burst pipe in a rented flat is an expensive conversation with a landlord.

Which Mode Suits Your Flat?

Korean boiler makers do not agree that one mode is always cheaper. They agree that it depends on the building.

Rinnai's manual, as quoted by Segye Ilbo, puts it in one line: use room-temperature heating when the controller is out of direct sunlight and not affected by heaters; otherwise use floor heating. Navien's version: room mode if the home is well insulated, ondol mode if it has draughts.

If you are not sure what you have, our winter bills guide has a table showing how to tell an individual gas boiler (a wall unit on the balcony or in the utility room) from district heating (no boiler, a valve box by the door). It matters because district heating bills come through the management fee, not a gas bill.

Hot Water Is Often the Biggest Gas Cost

The floor is not always what drives the bill. Korea's gas trade press put it bluntly: the highest household gas bills come from setting the hot-water temperature high and running the water pressure hard (가정에서 보일러를 사용할 때 가장 가스비가 많이 나오는 경우는 온수온도를 높게 하고, 수압을 강하게 할 경우다). Long, hot, high-pressure showers can cost more than a well-set floor.

Three practical habits follow:

1. Turn the hot-water temperature down on panels that let you set it, so you are not mixing scalding water with cold at the tap.
2. Shorter showers. The Korea Energy Agency has estimated that cutting a shower by five minutes saves about ₩6,830 in heating-related energy cost (as reported by Segye Ilbo, December 2025; the period the figure covers was not stated in the report, so treat it as indicative).
3. Keep humidity at 40–60%. Seoul's heating guidance says moist air holds heat and cools more slowly, and that blocking draughts can raise the indoor temperature by 2–3°C.

What a Winter of Floor Heating Costs

Korea has no progressive tiers on residential gas, unlike electricity. You pay one unit rate for what you use plus a small fixed charge, so the arithmetic is simple.

As of 1 September 2026, residential city gas in Seoul is ₩22.5268 per MJ plus a ₩1,250 per household monthly basic charge (기본요금), with VAT added on top. Seoul left the household rate unchanged at that revision while raising business and industrial rates. Other regions differ, because the retail portion of the tariff is set region by region, so a Busan or Gyeonggi bill will not match a Seoul bill exactly.

For scale, our winter bills guide works through January bills at the Seoul rate. On its assumptions (42.7 MJ per m³, VAT included), a careful one-room using 40 m³ of gas comes to about ₩43,700, and a two-room villa using 100 m³ about ₩107,200. Those usage levels are illustrations, not averages; your own previous January bill is the better guide, so ask the landlord or agent for it before you sign. The same guide explains why an electric heater costs roughly two and a half to nearly four times as much per unit of heat as gas.

The energy voucher, and why most foreigners cannot get it

Korea's 에너지바우처 (energy voucher) helps low-income households pay for heating and cooling. For 2026, Seoul's notice gives annual totals of ₩295,200 for a one-person household, ₩407,500 for two, ₩532,700 for three and ₩701,300 for four or more, usable from 1 July 2026 to 31 May 2027, with applications open until 31 December 2026 at the local community centre or online through Bokjiro.

Eligibility has two parts, and both must be met: the household must receive livelihood, medical, housing or education benefits under the National Basic Livelihood Security Act, and it must include a qualifying member such as an older person, an infant, a person with a disability, a pregnant woman or a single-parent family. Foreign residents can only be benefit recipients under that Act in narrow cases, for example some foreign spouses of Korean citizens. For anyone on a work or study visa, the realistic answer is no. If you think you may qualify, the voucher call centre is 1600-3190.

Ondol: The Warm Floor Behind the Habit

The boiler panel is the modern end of a very old idea. Ondol is the traditional Korean heated-floor system. In older forms, heat and smoke from a firebox travelled under a raised masonry floor through flues before leaving through a chimney. The stones absorbed the heat and radiated it upward, warming the room from below. For background, see ondol and the related agungi firebox.

Modern apartments replaced the smoke and stone with a gas boiler, or a district-heating pipe, and a loop of water pipes set in the floor screed. But the logic is the same, and so is the main lesson for the controller: a heated floor is a thermal mass. It is slow to warm and slow to cool. That is why hosts ask guests not to swing the panel up and down, and why holding a steady setting usually beats switching off and reheating.

Furniture habits followed the heat. If the warmest surface in a winter room is the floor, then sitting, sleeping, eating and gathering close to it makes sense. Low tables, floor cushions, thin mats and folded bedding all belong to the same logic. Korea also extended the idea to the bed itself: see our guides to Korean heated mattress pads and the Korean stone bed.

Shoes Off: Why the Floor Is Clean Space

Koreans take off shoes indoors because the home floor is treated as clean, usable living space. People sit, stretch, eat, play with children, fold laundry, sleep and relax on or near it. Outside shoes bring dirt, rain and street residue into that space. And because the floor is also the heater, it is the surface people want to touch.

The entrance area (현관, hyeongwan) is the boundary. The lower step or tiled area is where outside shoes stay; the raised floor beyond it is the clean zone. You can usually read it from the architecture even without the word.

As a guest, the safe routine is:

1. Stop at the entrance.
2. Watch where the host puts shoes.
3. Remove yours before stepping up onto the raised floor.
4. Leave them neatly, toes pointing toward the door if there is room.
5. Wear guest slippers only if offered.
6. Make sure your socks are clean and hole-free.

Bathroom slippers are the one pair with a fixed address. If plastic slippers are sitting inside the bathroom, they belong to the bathroom. Carrying them, and the wet floor with them, back into the living room is the foreigner mistake that gets noticed.

Suitcases follow the same rule as shoes. The wheels have rolled through stations, streets and airport toilets. Leave luggage near the entrance or wherever the host shows you, and wipe the wheels if it has to cross the floor.

Living on the Floor Means Living With Floor Noise

If the floor is where people sit, play and walk, then the floor is also how sound reaches the neighbours. Korea treats this as a legal matter, not just a social one, and the thresholds are published.

Under the 공동주택 층간소음의 범위와 기준에 관한 규칙 (Rule on the Scope and Standards for Inter-Floor Noise in Multi-Family Housing), Article 3 and its attached table, the limits are:

The exclusion is the part that surprises people: noise from bathroom and plumbing water use is explicitly outside the definition. A neighbour's shower at 2am is not, legally speaking, inter-floor noise in Korea. Footsteps at 2am are.

There is also a free government route before any of this becomes a dispute. The 층간소음 이웃사이센터 (Inter-Floor Noise Neighbour Centre), run by the Korea Environment Corporation (한국환경공단), takes calls on 1661-2642, weekdays 09:00-18:00. The process goes phone consultation, then a scheduled visit, then on-site measurement if it is still unresolved, then mediation guidance. Applications also go through the National Noise Information System at noiseinfo.or.kr.

For a visitor this is background. For anyone moving into a Korean apartment it is the practical consequence of floor culture: you will hear the family above you, they will hear you, and the numbers above are the line at which "annoying" becomes "actionable." Soft indoor slippers are, among other things, a courtesy to the flat below.

Low Tables, Floor Sitting and Floor Bedding

Low tables in Korea are not museum furniture. They hold fruit, tea, late-night delivery food, homework, laptops and board games. Some restaurants still have raised floor seating where shoes come off, though many now offer chairs or both. Jjimjilbangs, hanok stays and pension rooms often use floor mats and low tables.

For visitors the challenge is physical. Knees, hips and backs complain if you are not used to it, and that is not disrespect. If you need a chair, ask. The trick Koreans use is height: a thick square floor cushion (방석, bangseok) lifts the hips enough to take the load off the knees. If you want the same at home, a firm square pad such as the Verpert 25-inch floor cushion does the job.

When sitting at a low table, avoid stepping over food, pointing your feet at dishes or people, or putting bags on the eating surface. If bedding is laid out on the floor, do not walk across it in outdoor socks or put luggage on it.

Modern Korean homes are also not hanok. Most have beds, sofas, desks, robot vacuums and kitchen islands. The point is not that Koreans live on the floor all day; it is that the floor stays usable, flexible space in a way it rarely does in shoes-on, carpeted homes.

Hotels, Hanok Stays and Rentals

International hotels feel familiar: beds, Western bathrooms, and staff who do not expect you to know household customs. Even there, many Korean guests change into slippers.

Hanok stays are different. "Traditional room" or "ondol room" (온돌방) in a Korean listing usually means floor bedding and no bed frame. That is a room type, not a downgrade the property will fix on arrival. Decide before booking, and see our guide to Korea hotel and Airbnb cancellation rules for what the official refund table allows if you change your mind.

If you are renting for months rather than nights, ask three questions before signing: is heating an individual gas boiler or district heating, what did last January's heating cost, and where are the boiler and manifold valves. Our guide to rent in Seoul covers deposits and contracts. And for more everyday etiquette, see the Korea coin laundry guide, the Korea temple stay guide and the guide to what to call a stranger in Korea.

FAQ

Q: My Korean boiler is set to 50 and the room is not hot. Is it broken?

Probably not. If the panel is in 온돌난방 (ondol) mode, 50 is the temperature of the water circulating under the floor, not the air, and 40–50°C is the normal winter range. If you want to control the air temperature instead, switch to 실내난방 and set about 20°C.

Q: Which is cheaper, 실내 or 온돌 mode?

It depends on the home. Navien recommends room mode for well-insulated homes and ondol mode for draughty ones. Rinnai's manual says use room mode only if the controller is out of direct sun and away from heaters, and floor mode otherwise.

Q: Should I use 외출 (away) when I go to work?

No. Seoul's guidance is to set the heating 2–3°C lower than usual for a normal day out and to use 외출 only for absences of three days or more. Reheating a cold floor slab uses a lot of gas.

Q: Can I switch the boiler off completely when I travel in winter?

Do not unplug it. Kiturami's freeze protection, which starts the pump at 8°C and the burner at 5°C heating-water temperature, only works with power on. Use 외출 and leave the gas and manifold valves open.

Q: What does 온수전용 mean?

Hot water only. The boiler heats tap and shower water but not the floor. It is the summer setting, and the most common reason a floor is cold in December.

Q: How much does Korean floor heating cost?

Residential city gas in Seoul is ₩22.5268 per MJ plus ₩1,250 a month, VAT on top, as of 1 September 2026. On illustrative January usage, a careful one-room comes to roughly ₩44,000 and a two-room villa roughly ₩107,000 (EpicKor calculations, see the winter bills guide).

Q: Can foreigners get Korea's energy voucher?

Rarely. It requires National Basic Livelihood Security benefits plus a qualifying household member, and foreign residents can receive those benefits only in narrow cases, for example some foreign spouses of Korean citizens. The call centre is 1600-3190.

Q: Why do Koreans remove shoes at home?

Because the floor is clean living space where people sit, eat, play and sleep, and because with ondol it is also the heater. Outside shoes stay at the entrance.

Q: Is there a legal limit on noise through a Korean floor?

Yes. Direct impact noise such as footsteps is limited to 39 dB during the day (06:00–22:00) and 34 dB at night, with peaks of 57 and 52 dB. Airborne noise from a TV or speakers is 45 and 40 dB. Bathroom and plumbing water noise is excluded. The free mediation line is 1661-2642.

Bottom Line

A Korean boiler panel is simple once you know the one rule: in 실내 mode the number is the air, and in 온돌 mode it is the water under the floor. Set about 20°C in room mode or 40–50°C in floor mode, pick the mode that suits how draughty your flat is, turn it down a few degrees rather than to 외출 for a day out, and never cut the power in winter.

The rest of Korean floor culture follows from the same warm floor. Shoes come off because it is clean living space. People sit and sleep low because that is where the heat is. And the neighbours hear you because you live on it. Start at the entrance, respect the bathroom slippers, and treat the floor as part of the room.

Sources

• Seoul Metropolitan Government, public utility price page (서울시 물가정보 - 공공요금 - 도시가스): residential city gas ₩22.5268/MJ, 0.00% change, ₩1,250 per household monthly basic charge, effective 1 September 2026; checked 21 October 2026. https://sftc.seoul.go.kr/seoul/mulga/main/contents.do?menuNo=200012
• Seoul Metropolitan Government climate and environment news, "지갑도 지키고, 지구를 보호하는 겨울철 난방비 절약 TIP" (updated 13 January 2025): 20°C winter indoor temperature, 15%+ cost per degree above 20°C, 7% saving at 19°C, 외출 only for absences of three days or more and 2–3°C lower otherwise, draught-blocking and 40–60% humidity. https://news.seoul.go.kr/env/archives/561585
• Segye Ilbo, "실내 vs 온돌난방은 단열 등 고려해야…지역난방, 장기간 안써도 켜 놔야" (1 December 2025): Kyungdong Navien's room-versus-ondol advice and setpoint example, Rinnai's manual guidance, and Korea District Heating Corporation's three-day 외출 advice and keep-controllers-on rule. https://www.segye.com/newsView/20251201501679
• Segye Ilbo, "난방비 아끼려다 '큰돈' 든다…보일러 망가뜨리는 사용 습관" (13 December 2025): Korea Energy Agency estimate of about ₩6,830 saved by a five-minute shorter shower. https://www.segye.com/newsView/20251209516826
• Etoday, "귀뚜라미, 한파 대응 난방 전략 공개…동결 사고 예방 강조" (21 January 2026): Kiturami two-stage freeze protection at 8°C and 5°C, keeping power, gas and manifold valves on, and an 18–21°C winter indoor recommendation. https://www.etoday.co.kr/news/view/2547648
• Kyungdong Navien, "나비엔 스마트" app listing (App Store, Korea): boiler modes 실내난방, 온돌난방, 온수전용, 외출, 난방 반복예약 and 난방 24시간 예약; customer centre 1588-1144. https://apps.apple.com/KR/app/id1621968030
• Financial News, "귀뚜라미, 가스보일러용 와이파이 실내온도조절기 2종 출시" (10 January 2019): heating, ondol, timer, hot water and away as the basic controller functions. https://www.fnnews.com/news/201901101031510872
• Gas News (가스신문), "가스절약 위한 가정용보일러 실내온도조절기 사용법은", Yang In-beom (2021): 40–50°C ondol and 20–22°C room settings, and hot-water temperature and pressure as the largest household gas cost. https://www.gasnews.com/news/articleView.html?idxno=94991
• Seoul Metropolitan Government climate and environment news, 2026 energy voucher notice (updated 13 August 2026): amounts by household size, eligibility, application deadline 31 December 2026 and use period to 31 May 2027. https://news.seoul.go.kr/env/archives/570227
• Kyunghyang Shinmun, "국적은 있어도 권리는 없다", opinion column by lawyer Lee Jin-hye (24 August 2025): foreign parents in a legal marriage who raise minor children can qualify for basic livelihood benefits; unmarried foreign parents cannot. https://www.khan.co.kr/article/202508242101005
• Ministry of Government Legislation, Easy-to-Find Everyday Legal Information (찾기쉬운 생활법령정보), "층간소음 분쟁": thresholds under the 공동주택 층간소음의 범위와 기준에 관한 규칙 Article 3 and attached table, including the exclusion of bathroom and plumbing water noise. https://www.easylaw.go.kr/CSP/CnpClsMain.laf?csmSeq=1409&ccfNo=1&cciNo=1&cnpClsNo=1
• 층간소음 이웃사이센터, Korea Environment Corporation (한국환경공단): service description, 1661-2642, weekdays 09:00-18:00, and the consultation-to-measurement process. https://floor.noiseinfo.or.kr/
• Daiso Korea online store (다이소몰), 슬리퍼형 학생 실내화: ₩3,000, EVA, checked September 2026. https://www.daisomall.co.kr/pd/pdr/SCR_PDR_0001?pdNo=1040882