People are forgetting an important lesson

I've seen hay bales catch fire from being too wet, no way I'm building a house out of that.

Yeah, same as wood, who would build houses out of that? /s
Hay is great insulation and it's sealed with protective material anyway in modern houses. Also, even if not: Some tribes make houses out of hay or straw and those houses are quite great in their particular circumstances. There are experiments to use hay bales for structural support as well and it holds up surprisingly well.
Also, fun fact: wooden houses are less dangerous in case of fire than houses made of steel and concrete because the steel rod reinforcements start becoming soft at low temperatures (~200°C) and crash. Wooden houses announce crashing when burning, concrete buildings don't.
- Something something jet fuel...
  
  I knew it!
How does that work? Too wet with kerosene?
- The moisture and organic material causes mold and bacteria to form and create heat. Because hay is a good insulator, heat will build up more and more. Once the hay gets to a certain temperature flammable gases are formed and can combust from the heat.
  
  And as the heat raises, it becomes perfect for other bacterias, which start to multiply too, increasing more the heat
- Sun goes through droplet of water. Focuses beam. Burns the highly flammable straw.
Straw is compressed in the walls, so not to let oxygen go through, and it doesn't get wet as the wall is covered with clay inside and outside.
- But the moisture content of the straw matters BEFORE it gets sealed. A stack of a thousand damp bales can heat and combust. And it's the interior damp bales that heat and start the fire.
  They can get wet waiting for transport to the jobsite, they can get wet during transportation, and they can get wet during building.
  I'm not saying a strawbale house can't be well built, but it's not a "one size fits all" solution for every location.
  
  Yes, of course it has to be dry.
  
  And that is the trick isn't it. A piece of wood gets rained on, it isn't effected much if at all. When the sun comes out, it dries in less than an hour. But bales are much like sponges, they soak up water easily and dry out very, very, very slowly.
  Just how much do you try the average construction crew to keep those bales dry on a job site?
  
  Building clay-and-straw houses is not suitable for mass construction, I guess.
  You could say you need to live on the site :)
  
  It is on par with building a ground up stick house. Sure it doesn't beat any kind of prefab or cook cutter houses. But neither does any other method.
  
  No they probably aren't suitable for mass use. But, for one-offs they can be viable choices if you get a high quality contractor and construction crew that knows what is needed to build the structure correctly.
  
  The ones I saw were built by volunteers :D
  
  Were they volunteers from the local pub?
  
  No, from international civic service.

Better than wooden houses. source

So flammable mater + low airflow is somehow more fire resistant than flame resistant mater + low airflow? Looks like the source is pure marketing unless their comparable insulation is perforated cardboard coated in fuel gel.
- Roof/attic often uses rockwool or glasswool. Wall insulation is often something like XPS, PIR or PUR.
  Although it sounds counterintuitive, I can see straw doused in flame retardant being better than supposedly flame retardant polystyrene foam made from hydrocarbons. I mean, just look at what happened with Grenfell Tower.
  
  "doused in flame retardant" isn't mentioned in the source as far as I saw, plus it would affect the eco-friendly, workability, cost effectiveness, and biodegradability benefits mentioned (though the last one is worthy of debate as a pro or con in the first place). Everything has its tradeoffs unfortunately. This could be the better side for some surely.
  
  From what I have read they are using a loam layer on both sides of the wall, I doubt that this affects eco-friendliness and biodegradability. And they are F90 certificated. source
  
  flame removedant
  lemmy.ml is replacing some of your word with another one. Good ol' Scunthorpe problem!

From the article…

Since straw bales are tightly packed, they do not burn as easily as certain other materials. The tight packing reduces airflow, something that is critical to sustain a fire. While there is some fire risk during the construction phase (as is the case with many building materials), once the home is finished, it’s flame retardant nature decreases the risk, usually resulting in a home that better resists burning than a traditional stick built house.

"...better than a traditional stick built house"
I'm thinking of brick, what do we think folks? Seems like we have three possible building materials with one clear winner amirite?
- Only the big bad wolf can help us decide
- I don't see how brick is the "one clear winner".
  A straw and clay house is better insulated and you need no cement. It has pros and cons.
  
  Try taking out Big Bad Wolf insurance in a stick house bud
  
  I live in center Europe, here people don't insure houses.

Well hemp bricks hold up well so I am guessing they improved upon this too to be more fire retardant

Man I'd love a hemp brick house.

If it's treated with a fire retardant like sodium borate, pretty well. They use the same chemical for cellulose (shredded newspaper) insulation.