온돌 (Ondol) An ancient original form of heating with wood...

I have been battering around how to start this post for months now...and with the joining of a knew member asking me about fitting post to stone plinths, it brought up all my notes yet once again...

I have written long and complicated descriptions, and all types of "good stuff" but as I read through it...most would get board or lost in the minutiae of the info...so...I am just going to take what is already out there and "blitz" the readers of this post with info...

If you have questions...I do my best to respond...

Regards,

j

Links to get you started:

온돌

구들

This is a link of an acquaintance of mine I met online and photos of him building with students a modern Ondol.

Photo Group 1

Photo Group 2

I followed some of the pictures in the first link, and thought these were particularly interesting:

A brief English-language explanation with simple pictures:

http://www.emagasia.com/korean-ondol

This one has no English content, but the picture is gorgeous:

http://soslbee.egloos.com/viewer/3395678

This one seems to be from an expo, including the clay model, and some modern conductive parts that seem to be used for cast-in-place hydronic floors.

http://kr.aving.net/news/view.php?articleId=116515

And a blog, probably someone who's getting one installed at home - again, no English content.

http://blog.daum.net/ondole/2

An ancient version, presumably:


I am fascinated. Particularly love the conductive base plates for hydronic flooring, seems like it would make a light-weight mass floor much more efficient at heat transfer than our wood-dominated floor industry.
It makes me want to collect a bunch of muffin tins and see if it would work.

-Erica W

I'm excited by the idea of combining a rocket mass heater or Finnish Counterflow masonry heater feeding into an ondol floor above it, then up a chimney and out. This might give complete combustion, and warm steady floor heating, without takng up room in the heated room, and would keep firewood and ashes out of the warmed space.
Here's a link to the wikipdia Ondol entry: en.wikipedia.org/wiki/Ondol
Here's a link to a masonry heater association: http://www.mha-net.org/

Erica Wisner wrote:I followed some of the pictures in the first link, and thought these were particularly interesting:
And a blog, probably someone who's getting one installed at home - again, no English content.

If you can afford that much copper for a heat system at current prices, just burn dollar bills to keep warm.

Like roman hypocaust! Heating systems like that are 2000 years old!

Hi Jay.

I have searched for info regarding dimensioning an ondol system but my korean fu is non existant.
Google likes whales and canis lupus but i don't know how they fit the ondol system

This system has proven itself for a long time and Korea is in a similar climate to me so it's very applicable.
Also it's simple to operate.
Advantage over similar radiant systems like hydronic heating is that there is nothing to break (like pumps and tubing) and need no modern means to function (like electricity).
All you need is something to burn (some wood).

The only "improvement" that i might do is the actual burning chamber.
Like Brian, i would put a rocket stove because of it's burning efficiency and little smoke.

Any info regarding calculus/empirical data about dimensioning such a system is extremely welcome.

Hello Ionel,

I am afraid anything I know of or have learned the most from regarding this wondrous wood burning masonry heating system is either in Chinese or Korean...including any "calculus/empirical data about dimension such a system." Most of my small experiments have been pure empirical copy of what i could extrapolate from graphics, translations, and the few I have seen.

They are a marvelous system, that I don't really see as that much different than a form of a RMH.

Regards,

j

I have downloaded pretty much all info/images/videos i could find on the subject.
The design has some smart things going, like the turbulence creating "humps" on entrance and exit.
Also it seems the height of the channels is important.
If they are 200mm, the heat will be transferred to the floor and ground equally.
But if the channels are 400mm deep, then heat will naturally flow more on the top therefore heating the floor more than the ground.

Anyway, my first priority is to determine what size burning chamber is needed for a certain size room.
Usually, the rooms i have seen heated like this are small.
But temples also had the ondol and they were fired by multiple burning chambers.

Regardless of this, an addition would be the "ondol bed" as seen here.
This way you heat the floor less and more the bed.
The local vernacular style has similar properties since behind the large oven/stove there was a small space used as bed for old/ill people or children since it was warm and nice the whole night.

PS
Since the floor of this system is usually made of pretty soft material, hydronic tubing could be installed in the top layer, as a back-up.
This would only be used on early fall/late winter when it's pretty cold outside to require heating but enough sun to heat the space.
A direct gain would be best but sometimes this cannot be achieved due to the roof overhand or something else.

Hi Ionel,

But if the channels are 400mm deep, then heat will naturally flow more on the top therefore heating the floor more than the ground.

Yes, this seems to be more the norm (but not always) depending on the intent of the heating systems. It seems that those that are more "within" the confines of the structure may be of the 200 mm rang as then the heat energy is stored in both the floor, and the surround masonry and ground to be released more slowly, while others are taller and do heat the floor itself more rapidly.

Anyway, my first priority is to determine what size burning chamber is needed for a certain size room. Usually, the rooms i have seen heated like this are small. But temples also had the ondol and they were fired by multiple burning chambers.

I think (without a great deal of research and expensive experimentation) it may not be advantageous to try and "read-in" or "reinterpret," what these original Ondol forms did or how they functioned. I would suggest building the most simplistic form possible, with element designed into it that would facilitate modification and/or upgrade. Multi burn chambers is a very advanced design element that I am not sure I would risk if I only had one system, and that system was one of my primary heating sources.

I would also note, that the "intent" of these devices where not meant to heat, "certain sized room." This is a common misperception and "read-in" to what these did and how they functioned within the Asian cultural construct. They can (and often did) heat a space to some degree in the less cold times of a season, or when a room was closed in for an evening, however there intent was only in heating the floor itself, and no other intended burden was expected of them. No other demand or expectation was placed on them, beyond heating the floor itself. The intent was to sit on a raised dais that had a Kang or Odol heater attached and often a blanket, or other cloth shroud was draped around the occupants shoulders to further trap heat radiating from the floor. Many time the room itself was rather open, if not actually completely open to the outside elements with large veranda or portico and sliding wood and paper doors.

I am not saying that these couldn't be used as such a device as heating a room or that some forms of this device in history did not function rather well for this purpose, like the Roman Hypocaust, but most only had a limited expectation of heating the floor alone, and any heat benefit to a rooms ambient air temperature was only a residual effect...not primary. Just like a RMH, the goal is to heat it mass, then have that radiant into a room, yet the scope and range of these devices to heat an entire home may be limited and/or must be very well planned out to achieve such goals.

Many structures from Eastern Europe through to Northern Asia all had similar devices from just a single masonry heater with attached bench/bed to some structures with both in-floor, bed and multiple room/burn chambered devices. Start small and build up would be my primary advice at this time. As you learn how these systems draft, perhaps more adventurous approaches could be explored.

Since the floor of this system is usually made of pretty soft material, hydronic tubing could be installed in the top layer, as a back-up. This would only be used on early fall/late winter when it's pretty cold outside to require heating but enough sun to heat the space. A direct gain would be best but sometimes this cannot be achieved due to the roof overhand or something else.

Many of the floors in Korea (as the rooms themselves) are often covered in paper, which is a wondrous decorating and finish material in many forms that it comes. Even simple earth floors that would otherwise not be as durable, can be made so with the addition of a paper laminate finish. I have always said that I would incorporate more "paper" into my work as time goes on. I also would try very hard if ever designing and building one of these systems again, to incorporate perhaps a hydronic system of some form into all or a portion of it. These systems are built with clay, lime and related materials so leaned themselves well to such simplistic adaptation. As for roof over hangs, even really large ones (if the home is well designed to fit its specific biome) will not effect winter solar gain at all. This is why I am so adamant that DIYers actually understand more than they often do about attached "solarium and green houses." Understanding where the summer and winter soloist points are on a building site and at what height to place fenestration within structures is so vital. This knowledge and wisdom was never lost on our forbears.

I should share here, as it has come up as of late, that I I am not opposed to "slab work" (I don't like OPC and what it does to the planet) if they are the only "good alternative" for a tight budgeted project, if them must be employed. When geopolymers/limecretes become more common, as they will!, then these slabs may well become best practice for certain designs...Often they are not as inexpensive as many suggest. A raise earth foundation of tectonically stabilized gravel, stone plinths with packed clay earth and raised wood "floating floors" in the 청마루 (Korean Cheongmaru) style can be in the same cost range as many slabs if built by the owners and some could (and have) lent themselves well to the formation of underfloor heating systems.

A heavy Korean Maru floors could be created from most of the woodlot found on many permie building sites or anywhere there is trees, and it doesn't have to be "kiln dried" or even supper high grade lumber. Traditional Korean maru (maru=floor) floors, one form being Cheong Maru 청마루 have been around for millenia, and some are even of stone and allow for radiant heat underneath in the form of an Ondol 온돌 or perhaps hydronic tubing! The mass of these floors is very high when of stone, and both insulative and massive when made of wood. Getting to the tubing, flues space, or to service/check or to mechanicals and electrical elements that are often hidden under floors is just a matter of moving some "magic boards" around as this is an "all joinery floating floor system" of both timber and wood plank or masonry units. Learning the designs and functions of these systems could greatly broaden the function of many "permie" heating systems.

I am extremely interested in the jointery floor. But having a hard time finding methods of construction, or general information outside of pictures. Any advice on how to further research this method? I tried my best with Kanji, but no luck. The language barrier and lack of western words, have me in a doldrum. I would like to try this method with solar heat collectors, pushing air through the floor, not to heat a space, but create a nice passive thermal barrier. In its own envelope. It could be easily retro fitted. If there is enough sun to heat the envelope, then there would be enough sun to power a small dc fan. A modern adaptation, "safer", and a nice experiment that the inspectors may roll their eyes at, but allow. It would only take a few inches of head space to retrofit.

I could even see drilling a few holes along the band board, in traditional modern homes, for a solar collector duct, and distribute heat inside of the floor joists.

Hi Chad,

I don't know of anyone that isn't Korean, or one of my students, that understand how to build these floors...sorry. I know of a few poor copies, yet these are "modern contractor" builds that only are a faux form of the original systems.

There is a reasonable amount online if one really looks for it, but this is very basic outlines and/or advanced methods and all of it is in Korean (Hangul is the term for Korean alphabet...Kanji is for Japanese...sorry if I was confusing on another post about that.) I may next spring teach a work shop with someone like Bill Bradbury on a form of these floors that DIYers can incorporate into projects.

I assure you I am not any type of "wiz" at languages, yet have been recognized as a fairly accomplished academic researcher, and knowledge holder of other cultures arts, crafts and cultural customs, as such there is a cascade affect in gaining deeper knowledge and making connections. Doing the "academic" side needs more "computer skill" and typing speed than knowing "English" as you have to do the "research" and "correspondence" with others in their language to gain the greatest insights. Then of course travel to them and learn directly or indirectly from those that go there.

Coding in or cutting and pasting the Hangul for specific terms is where one must start...or...what I use to have to do is get text and arduously translate to English where I could. With out a solid foundation in these traditional wood working skill sets, it can be rather difficult to extract and extrapolate all the information one would need to replicate a floor like this in a full traditional context, even though they are rather simple looking in view.

I should be able to answer specific questions, yet can't really get to all that is need by simple postings. This is a topic like timber framing, or green wood working and all I can do is "scratch the surface" as books are (I am trying) written on these many subjects.

I would like to try this method with solar heat collectors, pushing air through the floor, not to heat a space, but create a nice passive thermal barrier. In its own envelope. It could be easily retro fitted. If there is enough sun to heat the envelope, then there would be enough sun to power a small dc fan.

This sounds plausible, yet may cause the wood to move around much more than normal with such large ambient swings in temperature. I would suggest that only "quarter sawn" wood should be incorporated into such design as its tangential movement is less than in "plain sawn" wood. Perhaps a narrower span between joist and not using wood but stone or tile in place of the planking could serve better in such an adaptation.

"Venting ducts" can create a convective current yet these have there own challenges that I have found seldom ever work as expected or intended and not until we get into entire diaphragm matrix designs do convective currents work well it would seem or as intended (e.g. "rain screen" walls and "cold roof" venting systems) as these tend to be more traditional applications for such current and drafting.

Please post further query at 청마루 (Cheongmaru) Floor Systems.

Regards,

j

Hi Jay,

I would also note, that the "intent" of these devices where not meant to heat, "certain sized room." This is a common misperception and "read-in" to what these did and how they functioned within the Asian cultural construct.

You can tell i'm still heavy influenced by the conventional way of being/thinking ...

That aside, the local vernacular (and i think in many other parts of the globe) principle was similar.
There was no notion of heating the whole house as is today (we even have thermostats, right ?)
The heat was made where and when it was necessary and one really can not compare how such a space would feel against modern housing.

When i asked about the "sized room" i was thinking only about heating the floor of a certain size.
Most ondol floors i've seen are small but some medium. My target would be 12-16 square meter max.
I mentioned that the system was used in temples in a complex form just to show it worked at that scale.
I really have no intention of reproducing that.

Again, traditionally, when people had multiple rooms AND they wanted to heat them all (not very common), they would usually build a stove in each room.
The fireplace could fire it's own stove (in the same room) or another in an adjacent one or both, providing also cooking space or any combination of these.
Usual combination was the 2 rooms sharing 1 common wall. Fireplace for cooking in one room feeding the stove in the other room (used for sleeping) thru the wall.
But this system is a later one, not very old (at least around here).

So heating the floors of a number of rooms could be done the same way. Different fireplaces for each room, with the fireplaces situated in a special room or in the same.
Put fire only where and when you need it.
An improvement would be to have the desired floors heated only "slightly" and also having a raised dais used as bed that has it's own fireplace.
This way, at night when it's colder and people need to stay warm, more energy is going in the bed and not in the floor.

Many time the room itself was rather open, if not actually completely open to the outside elements with large veranda or portico and sliding wood and paper doors.

Well, if i'd do that in my climate i would be dead frozen.

Regarding air temperatures, i have studied the dynamics of radiant vs. convective heating and how the air temperature gets stratified in both cases.
Couple these situation with how human physiology works and a picture emerges.
When someone is heat radiated, air temperature is less important.
I've been outside on 10 centigrade with sun and it felt great.
Put that sun behind a cloud and bang, cold hits you.

So, i have no intent in heating the air as long as i feel comfortable (warm floor).
And if i put this heated floor inside a relatively insulated envelope with lots of mass, the consequence would also be a little "room" heating.
As you said before, there is not a lot of difference between having a RMH feeding a large cob bench or a cob dais/bed and the ondol floor.

If the koreans felt comfortable on a warm floor with paper doors and somewhat exposed to the outside, i don't see any reason why the same floor won't give a comfortable room ambiance inside a more insulated house.

Hi Ionel,

Think with the correct skill sets and motivation, many of the ancient Kang, Ondol, or Hypocaust could all be employed to your envisioned goals. I have often read (or been told) that "old building forms" are not adequately comfortable for modern humans. I can understand that perspective to only a certain degree, as most folks only see "old buildings" in very run down conditions. I do also think modern humans are much less hardy...

Well, if i'd do that in my climate i would be dead frozen...

That made me laugh......as it speaks to that "hardiness factor" I just mentioned above...or...the lack there of... I am not suggesting that "vintage living" is for everyone, but I am very confidant that nobody would freeze at all if they had a more "holistic" existence with the world around them, and "lived" more outside than in. One way of doing this is to design architecture that embraces this living style as many of our forbears did. Last winter the coldest nights were -30°C, and because I have slept outside most of my life, it was just like any other night during the winter moons.

Again, I am not suggesting that everyone "has to" embrace such a living style, yet believe our species is growing a tad soft from lack of exposure...

If the Koreans felt comfortable on a warm floor with paper doors and somewhat exposed to the outside, i don't see any reason why the same floor won't give a comfortable room ambiance inside a more insulated house.

I agree 100%...

Regards,

j

Hi Jay,

Talking about going soft ... you nailed it.
I wouldn't mind much for myself but the wife and kids ... well ...
My wife (and her mother) can sense even the tyniest air movement yelling DRAFT and throwing kithen utensiles to closa tthat darn wndow/door whatever.
Not to mention too hot/cold. This is i am afraid national "illness" ...
Now this will jam that natural ventilation strategy i was pondering (but that's another thread entirely)

Regarding old buildings not suitable for modern humans, that's as you said ...
That and the fact we got accustomed to living in aquariums ...

PS
Regarding cold, taht's ok. It's cold and wind i bother (both we get regularly) ...

I had the pleasure of 8 days touring Sth Korea with my daughter whom is at Uni in Seoul, in February. By choice we stayed in 'Hanoks'; traditional Korean homes, and I delighted in the ondol heating in each. With a move from sub-tropical to cool temperate shortly, I'm converted as to the livability of these systems. It's not unheard of Down Under, (hydronic underfloor heating) but it's rare enough that I've only walked on it a couple of times before. My daughter, 10 flights up in a share apartment in Seoul, says that they can tell when all the apartments around them turn theirs on, as they get heated up too! Sometimes to the point of having to open the windows to cool off!
I got a few photos of my trip over, I was fascinated by the wooden pieces on the floor - all totally removable. (I didn't try!) I was a little tickled by the stylishly printed bubble wrap on the rice paper doors, too!
I'm flumoxed as to how to add pics though - I don't have a website that I put them on, barring my facebook account.
We did get to spend a (very wet) day at one of the Folk Villages on Jeju Island. That was amazing. There I got pics of the original ondol systems.
Adrienne

Some pics from the Jeju Island Folk Village. Sorry about the quality, my Canon hates cloudy days!

Adrienne Wimbush wrote:I had the pleasure of 8 days touring Sth Korea with my daughter whom is at Uni in Seoul, in February. By choice we stayed in 'Hanoks'; traditional Korean homes, and I delighted in the ondol heating in each. With a move from sub-tropical to cool temperate shortly, I'm converted as to the livability of these systems. It's not unheard of Down Under, (hydronic underfloor heating) but it's rare enough that I've only walked on it a couple of times before. My daughter, 10 flights up in a share apartment in Seoul, says that they can tell when all the apartments around them turn theirs on, as they get heated up too! Sometimes to the point of having to open the windows to cool off!
 I got a few photos of my trip over, I was fascinated by the wooden pieces on the floor - all totally removable. (I didn't try!) I was a little tickled by the stylishly printed bubble wrap on the rice paper doors, too!
I'm flumoxed as to how to add pics though - I don't have a website that I put them on, barring my facebook account.
 We did get to spend a (very wet) day at one of the Folk Villages on Jeju Island. That was amazing. There I got pics of the original ondol systems.
Adrienne

Greetings--
just some clarification for some of the photos you uploaded:  

*0006 is 청마루...so isn't heated
*0014 isn't actually rice paper, but simply "frosted" glass on a wooden framed door.  If the design wasn't manufactured onto the glass at the point of fabrication there's a ton of different patterns available to block vision in the form of adhesive (plastic) film rolls.  The bubble wrap is simply a budget workaround in an attempt to bleed less heat.
*0030 is a wood fired modern ondol system, note the manifold system to the left, usually valves are integrated so you can "turn on/off" rooms if you don't want to heat certain parts of the building.
*0021 appears to be a non-kitchen burn hole (note the cones as fuel next to it, as a starter)
*0022 is the kitchen with the 가마솥 kettles, under and to the back of the kettles the heat/smoke goes into the underfloor chamber(s) heating the next room
*0033 the kitchen is situated lower than the rest of the ondol system to keep in line with the heat/exhaust path.  there are also usually elevation features within the system to account for "drainage" of heavier gasses (the cold and humidity) from the underfloor chamber keeping in line with this pattern.

Additionally, if folks are looking for more resources on constructing these types of systems, there is a fellow who publishes many (many!) lectures on youtube detailing DOs and DON'Ts--however be forewarned that he goes over many of the DON'Ts and don't take them for systems that he is suggesting... (and take those auto-generated subtitles with a block of salt).  He runs an Ondol "Research Center" up in Gangwon Province.  There is a different guy who runs another Ondol "Research" Center just 15 min away from where I work, however I haven't been able to pin him down to ask questions....seems very insistent that I take his course.  Here all the videos are there for the taking.  Enjoy.
Myeong-hwan Kim's Ondol Lectures

I was reading up on Japanese and Korean architecture and came across the ondol floor and knew permies would know about it and have similar rmh ideas.

I have been thinking of making a jig that made under and over lapping clay slabs to cover a rmh heated ondol. Anyways, if you want to watch something about making a wooden daecheongmaru, you can watch a YouTuber named mr chickadee. He does everything traditionally and is American, though his videos have no speaking and rarely have text. He has some description of the work, but if you know traditional woodworking, it’s fairly simple to understand.

Here is an interesting video about hanok, the traditional Korean house. It has quite a bit of good information in it including ondol.

David Merkel thank you for the wonderful video of ondol and hanok. WOW we have so much to learn and do better. red clay heats AND cools better than anything? Paper doors breathe and insulate better than glass.

That was a beautiful video of a traditional system. I like that it will work without electricity. However hydronic floor heat and careful ventilation design can be awesome.

Pretty interesting video.  I wonder if their system of using large amounts of salt could be used in the underground house earth tubes to capture condensation too.

Was the large clay pot there to capture moisture that escaped the salt?

Not sure. The salt and pots seem pretty unnecessary to me. But whatever floats the boat.

My understanding is that some people have had condensation problems with their earth tubes leading to molds forming inside.  And so they have had to stop using them.

https://www.researchgate.net/publication/311850890_Design_and_Performance_Evaluation_of_Korean_Traditional_Heating_System_-_Ondol_Case_Study_of_Nepal

This looks like an adaptation of the Ondol heated flooring system to just use it as a means of cooking and capturing the heat in a thermal mass.  It's on top of the floor except I guess where they had to dig for the chimney and for the actual primary combustion chamber.  Construction is with locally sourced rocks and cob.  The chimney looks pretty short.  

And some sobering data https://www.koreatimes.co.kr/www/nation/2019/03/177_265143.html

A 1973 Korea Times article quantified the toll carbon monoxide poisoning had taken over the previous 15 years. According to the Korea Medical Association, "518,280 persons throughout the country have suffered yeontan gas poisoning since 1959. Among them, 24,990 persons have died."

Various factors were blamed including poor upkeep of the floors, low education etc that lead to tiny cracks in the floors leaking carbon monoxide.
Maybe this wasn't a problem when they used wood??

I want to incorporate a traditional ondol/gudeul system in a new tiny house. Are there any guides to designing ondols available preferably in english, or in spanish or chinese?

Hello there,
There is a contractor from Brittany (western part of France) who has upcycled the Roman hypocaust. Look for "Hypocauste XXI" on a search engine.
His idea is to use warm air (from pannels on the house's roof for instance) circulating thanks to a ventilator and not smoke through  the floor.
In this way there no risk of ending up poisonned up by C02.
Take care,

Here's a long video booster on ondol-writ-large; including hydronic underfloor heating as ondol. It does have good footage of traditional direct-wood-fired ondols in operation and in parts.

https://youtu.be/KggzIiVt3dU

Brian
-

This is amaqzing

i searched "ondol" on Youtube and this didn't come up.  Amazing find!

Hi Brian,

Welcome to Permies.