Help solve the mystery of the T-door

Here in the southwestern US and northern Mexico, ancient civilizations created entry ways shaped like a "T". Archeologists, such as the expert in the video below, call these doors an “enigma.” Knowing that many natural builders using stone, adobe, cob, wattle and daub have come up with ingenious approaches to keeping subterranean spaces warm in winter and cool in summer, it seems that our hands-on experts could help solve the T-door mystery.
As you can see from the photos in the slide show, the T-door has a narrow entry at the bottom, a wide opening on top, and the threshold to the T-door is slightly raised (like a submarine door). Thinking about laminar flow and cold heavy ground air rushing into a space to feed a fire, blocking that small low opening with something like a rolled up blanket seems like a good way to keep warm air in. Deflectors inside the buildings were used to keep the heavy cold air off occupants. Let’s put our heads together regarding this mystery: how cold the T-door keep occupants warmer in winter and cooler in summer?

Seems to me the least amount of cold air can come in low, and the most amount of hot air can flow out in summer and it provides great ventilation. Put a split door so you can open either half, you have a very versatile opening.
Think double hung windows and dutch doors.

Evidently, one person's theory was that the door would allow only one person to go in.

The doors are shaped like a tau so as to allow only one person to go through (Lúxan 1602, 73-74). The pueblo with T-shaped doors that Lúxan described

https://www.academia.edu/44957771/Ik_WAY_The_Mayan_Origin_of_T_Shaped_Doors_in_the_North_American_Southwest

Sounds good to me.

I also like the idea that cold air came in at the bottom and hot air went out at the top.

It could just be the most minimal opening practical. Any door\covering would have been made by hand, and such materials were more precious back then.

It could prevent many larger animals from entering.

It could force a person to enter slowly, giving a disadvantage to any enemy attacker.

Defense was my first thought.

I was reading a book which suggested that the many "tribes" in North America often had cultural differences that seemed to specifically set them apart from their neighbors, "we're us, and they're them" concept. It's how I always felt about religious dietary restrictions - some of them had at least a vague basis in food safety, but mostly it seemed like one way to define them. I realize that when working with adobe - even adobe bricks - the "T" wouldn't be that much more difficult to make, but the  idea that it was more a symbol than something practical fits what the images in the video. That said, it's possible he only showed images that supported his opinion rather than a full spectrum of variations.

Reminds me of the gateless fences where a person can step through, but animals will not because off the odd arrangement for their hooves/paws/etc.

As others have said, pretty hard to enter that door with a weapon in your hand on a deadly charge too.

Speaking as a father though, what a great way to have your twelve children living in the house and not have to yell at them for slamming the door!

Wonderful brainstorming so far!
By imagining living back in time a thousand or more years, some archeologists have theorized that the door shape is like the silhouette of a person carrying an oversized basket on their back: skinny legs and a large bundle. Imagining “the other” leads to all kinds of research papers about “them.”  
Yet, there is another approach to research that is a permies specialty: actually making something and studying it. Would anyone consider making a T-door to address a current, real-life, off-grid (or non-powered) problem? How could a raised T-door be an advantage to a room heated only by wood stove, fireplace, or rocket stove? In addition to the heat-ventilation-cooling example, someone here might be struggling with pests or would like to funnel certain animals into a trap for food or pelts. Does the T-door style offer solution to an actual challenge that anyone is experiencing now? How could the T-door be useful to you?

I don't know.  I like the cold air/hot air hypothesis.  But I'm seeing that it also allows the legs in at the bottom, but enough room for the torso to also carry objects in and out.  Kind of a human Tetris thing.

:)

Nissa Gadbois wrote:I don't know.  I like the cold air/hot air hypothesis.  But I'm seeing that it also allows the legs in at the bottom, but enough room for the torso to also carry objects in and out.  Kind of a human Tetris thing.

:)

That was my thinking.  It would be very hard to carry an armload of fire wood through a slot that size, but open it into a T and it would be much easier.

The issue I have with the cold\hot air hypothesis is that in order for any amount of air to enter, an equal amount must leave. This would be regardless of the shape of the door. I do wonder if the narrow bottom would possible create a narrow beam of cold air when it's cold out and send it straight to the fire instead of creating a cold draft all over the floor of the room. The radiant heat from the fire and the smallest possible door would help keep people warm. The wider top would let smoke out without it pooling up too much at the ceiling, but then it would be necessary anyway for a person to fit through. However, all this could be done by simply incorporating it into a removable door in a standard rectangular or arched doorway. That makes me think there's something else at play.

Judging by the size in the screenshot, I cannot imagine a person walking through the doorway with a large, especially heavy, basket on their back. It looks like a person would have to be doubled over to enter, unless they were a race of pygmies. And we once again arrive back at the point that a person could carry a basket through a full sized door even more easily, and with more options than these T doors. I think it's not about the wide top; it's something about the narrow bottom.

I can however guarantee something they did not do. They definitely did not carry a refrigerator, couch, table, etc. through them!

Jordan Holland wrote:
It could prevent many larger animals from entering.

I think this may be at least a part of the reason for the shape. It reminds me of squeeze stiles in dry stone walls of Northern England:

source
Sometimes these have steps up as well which would help keep smaller animals out as well as larger ones.

Great photo Nancy! That looks like actual usage of the lower part of the T to me.
The doorways to buildings vary in size. For more photos, skim the slide show in the first post. The T-doors can be very large, as in this photo by Russ Bodnar at Casa Rinconada in Chaco Canyon:

This room can accommodate hundreds of people. There is evidence that the space was warmed with fires inside the building and that the structure had some kind of roof.
For more information about Casa Rinconada, this Wikipedia entry with external photo links is helpful:
https://en.wikipedia.org/wiki/Casa_Rinconada

Hmm, Wow! that's definitely a bit big to keep out cows! I'll have to think again.

Amy Gardener wrote:Casa Rinconada in Chaco Canyon:

This room can accommodate hundreds of people. [...]

My first thought was the same as Anne, but the animal idea sounded plausible as well.  This seems to discourage both of those.

Though just going by the pic it may be an "evolution of design" thing.  From that pic it seems like the window to the right is very similar to the top of the T.  Possibly in early days all they had were windows to climb through.  Then somebody noticed, "hey, this would be a lot more comfortable if there was someplace for your legs to go."

In light of the range of scales, it seems highly probable that it acquired some symbolic importance beyond whatever functional benefits it might provide in the one person scale.
Knowing the timeline could help us know whether the small T openings were reflections of the large T openings and also symbolic rather than a primarily functional design.

Without knowing lots more about internal design, actual location details, orientation, it’s not possible for me to offer any possibilities based on anything but blind speculation.

Great point about needing more information, Peter! Check out the Crow Canyon Archeological Center
video lecture noted in the original post for this thread. Location maps, timeline, photographs and extra info is in the 50 minute lecture. Additional details about "internal design, actual location details, orientation" are available by checking out each site on Wikipedia (more info by following the external links provided on Wikipedia). Weather patterns for the specific locations are available by searching The National Weather Service.
However, what makes this inquiry relevant to permies is that someone may consider conducting primary research about the door. By making an actual T-door opening for a real building, we may learn first hand if the doorway actually offers some benefit to a fire-heated living space. We won't arrive at the answer by speculation.

Form follows function.



In the 60's and 70's, there is a travelling hawker selling rice and side dishes.
His wares were carried in two baskets supported by a flexible pole. He used
an unusual gait which allowed him to carry such loads further before tiring.
The bouncing load and some kind of harmonics made this possible. The art
is lost since most have gravitated into permanent premises that have bright
lights and several flat screens showing Qatar 2022 matches.



This picture is posted below. I haven't found out how to fix any picture
at the desired spot within this text.

The next two pictures show what I did to my front door. Most of the time
you don't have your house-keys at hand when you are burden with parcels.
Those hooks allow me to free my hands for this. I believe those ledges
at the doorway serve a similar purpose prior to the invention of S-hooks and
metal brackets, hinges and fold-down trays.

I wasted 59 minutes watching that video. There should be close-ups of
the aperture. I want to see the wear marks, scrapes and bumps.
I want to see a human traversing the door. I want to see what the
inhabitants were wearing what might require such an odd shape for
a doorway. I want to to see the ceiling. Fires will leave soot marks.
I want to see hieroglyphics that might indicate the use of those T-doors.

I found nothing helpful in that video. It almost seems like they are
hiding this from further scrutiny.

Thus, based on available evidence and existing contemporary events
like this,



The inhabitants must be some form of long lost bipedal hominid
mentioned in ancient texts as Spongia lascivius quadra braccas.

I wasted 59 minutes watching that video. There should be close-ups of the aperture. I want to see the wear marks, scrapes and bumps. I want to see a human traversing the door. I want to see what the inhabitants were wearing what might require such an odd shape for a doorway. I want to to see the ceiling. Fires will leave soot marks. I want to see hieroglyphics that might indicate the use of those T-doors.
I found nothing helpful in that video. It almost seems like they are hiding this from further scrutiny.

Thank you for wrestling with this “enigma,” Edward! I was similarly underwhelmed with the lecture. If as you keenly note, “form follows function,” how can we figure out what the function actually is?
There are many post-doctoral thesis’s that explore the symbolism of the doorway (function is to  tell people approaching from afar that we’re the T-clan). But I can not find anything about why people made the T-doorway from an improved shelter or comfort perspective. Many of the external signs that you want to see are lost to erosion. What is known is that these doorways are the entryways to multiple once-enclosed-spaces heated with indoor fires. The ruins exist.
While watching lectures and reading academic papers, I kept thinking, “why doesn’t someone just make a model of the door, live in the space for a period of time then submit their practical, hands-on, in-the-field findings?” The apparent absence of real-life experimentation with the T-doorway leaves an opportunity for discovery for anyone who is motivated to actually do a contemporary hands-on exploration by modifying the entryway to a hand-made earthen shelter.
Naturally, I am considering making the T-door unless some other permie has already done so.

Having known virtually nothing about this area and culture, I now know a very little more having spent (rather too much) time online today , and came independently to agree with this paper that concluded that there was a connection between Mayan culture and the T shaped doors. A t shape like this is a Mayan Glyph signifiying a god of wind and rain, which for an agricultural people in a fairly arid region would have been particularly important.

It is important for grasping the significance of the 'Ik’ to understand the wind and rain -- and, by extension, the connection between rain, the god of rain, Chaak (also Romanized “Chac”, and known as Tlaloc to the Aztecs) and wind. For example, in the traditional religion of the modern Yucatec Maya people, which has strong roots in the religion of the ancient Maya, a  prayer intended to summon rain states this inexorable connection explicitly:
"I also commend this food to the winds who come for the first time and for the wind that spies from behind the stones, without forgetting the great winds that emerge from caves. Lord, Chaak [sic], we call on all the rain gods, the lords of these winds. I offer this food to you. I also ask that the lords of the wind move the clouds so that they may water the milpas [i.e., cornfields] of their children" (Cámara and Preuss 1990, 130-144)

source
The Aztec god Tlāloc often seems to have the 'ik'symbol as earings for example:

https://en.wikipedia.org/wiki/Tl%C4%81loc#Representations

The speaker in the above lecture thinks that the reason the t doors were particularly in exterior walls were symbolic rather than practical (there appear to be separate high window vents for smoke outlets for example). It is likely that we will never know without more well researched artifacts after all this time though.

I did wonder whether there may have been a practical function in the doorway - whether for example a lack of door hinges may have made the shape better for a two piece door - solid at the bottom and a curtain at the top, but that is pure speculation. If it worked that way, you'd have thought that the style would be common elsewhere in the world, and I can't find much in drier areas of Africa for example. The only contemporary-rish features I can find are the front doors flanked by windows you sometimes find in 'between the wars' semi=detatched houses in the UK

(source)
Although, as can be seen in the above image, these tend to be archways which are stronger (and subjectively more attractive) than the wide t openings of the true t doors. I think these have their origins in prtacticality since these houses typically would not have had another window in the hallway, being typically very close to the neighbour they are nbot attached to, so having additional windows by the door lets in more light.

Peter Ellis wrote:Knowing the timeline could help us know whether the small T openings were reflections of the large T openings and also symbolic rather than a primarily functional design.

The canyon was occupied between 850 AD and 1250 AD.

The ruins were discovered in 1896.