Insulating wooden floor panel with straw

Thank you for the answer!
The patience is there, the construction horizon is within the next 5 years.

To maybe bring some clarity to your surprise:
I want to build sustainably, but that does not mean I want to accept things like insects in my house.
To make sustainable building accessible to the broad masses, solutions are needed that are a bit less off-putting (insects in the house).
And I am convinced, there are solutions! And natural raw materials can also contribute their part through appropriate constructive measures.

The mentioned statics is a good point.
I estimate a single-family house with 1.5 full floors and a gable roof is basically not excluded there.

Best regards

Thank you for the answer! The patience is there, the building horizon lies within the next 5 years. To perhaps give some clarity to your surprise: I want to build sustainably, but that does not mean that I want to accept things like insects in my house. To make sustainable building accessible to the wider public, it needs solutions that are somewhat less off-putting (insects in the house). And I am convinced there are solutions! And natural raw materials can also contribute their part through corresponding constructive measures. The mentioned statics is a good point. I suppose a single-family house with 1.5 full stories and a gable roof is basically not excluded there. Best regards

I understand you already, I am just aware of the frequently used term "sustainability." Of course, nobody wants many insects in the house, but proximity to nature, natural building materials, and fewer interventions in nature sometimes inevitably bring such things along. Furthermore, the question arises whether one should build new at all from the perspective of sustainability. A friend lives in Scandinavia in a dream location by the lake with lots of glass, views, nature, etc., yet he constantly struggles with the animals on and under the house (he has a construction style like you described). Since he initially leaves the plot as is, quite a bit of wildlife lives there, which in itself is sustainable and nice. He wants direct nature... but the way he would like it... and then it is no longer THE nature. I believe the "mass building sustainability" you mentioned will be difficult because they partly exclude each other. When you build, you should be aware that it will inherently be a massive intervention in the local nature, no matter what you put there. Once the excavator rolls in, sustainability is over. It is somewhat like Gerhard Polt described when the paint factory was allowed to build in the nature reserve and as an ecological measure had to plant wild vines on the fence. In general, I do not like the distinction (not by you!) that some build ecologically sustainably and others are the pigs with it. I am aware that with my planned building I cause damage to nature and that it is also ecologically nonsense to live on 150 sqm and more; nevertheless, I do it. But basically, I understand you that new solutions are always needed and we must try to leave as little dirt as possible if we absolutely want to build. But in my opinion, this is especially done through restraint, minimalism, and discipline.

Sustainable means building as small as possible, it doesn't have to be a tiny house, but also not 150 sqm+. Renovation or building gap.

With solid wood, pay attention to where it comes from. Ordering locally doesn’t mean it actually comes from nearby. Our walls partly came from Lithuania, partly from Austria, only the ridge beam came from the Spessart. Whether it actually grew there, no idea.
Similar with construction straw. Not that it is cut and pressed differently than normal straw and therefore only produced on large fields, which we partly don’t even have in Germany.

You will probably get the furthest with information if you try to find straw builders and contact them directly. It is not a run-of-the-mill building material.

I am "also" not an expert, but I have repeatedly faced such questions throughout my life and can well understand the conflict.
I consider "as little poison as possible" in the house to be a wise attitude.
A sticking point can be: "What is actually poisonous and what is harmless?" There are quite significant differences in the assessment.
And:
Not fearing mice and insects does not have to mean inviting them into the house.
I also do not find it stupid to research the possible disadvantages of natural materials.

The straw is surely not simply "laid under the floor," but somehow processed. Pressed, mixed with a binder, or something like that?

What I have found out is that wood fiber boards are currently very popular because they have so many good properties and are available for the most diverse purposes.

They will be used by me soon. (for the attic, not under the floor, but under the ceiling)

A "straw house" stands not far from here. I sometimes observed the construction and found it quite "sympathetic."
Straw "works" in any case (however, the walls were at least half a meter thick).

Thank you for the thoughts! A real straw house (for which there are already examples) would not be for me, I really can’t warm up to the idea. Also because solid wood walls convince me in every point (well, maybe not in terms of costs). Wood fiber is certainly interesting! But also clearly more expensive compared to straw bales. And for the floor slab (no basement) and the roof, very thick insulation layers simply don’t bother me..

What would the plan be?
Is the straw simply "filled in," or are there any preparatory processes it goes through?

Filling it untreated would be too risky for me (based on gut feeling).
I think it needs some kind of flame retardant and compaction.