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On the topic of 3d printed houses: In my home country of soviet canukistan, concrete walls with lots of little gaps would be destroyed by freeze-melt cycles.

Another major issue with concrete in climates like mine is that the concrete will shrink and expand with weather -- going from +40 to -40 and back a bunch of times has a real chance of just cracking because there's nowhere else for the material to go but apart.

I've seen videos talking about how strong concrete is, and one video even showed someone trying to break the concrete wall with a sledgehammer. Thing is, the same strength becomes a weakness when it's brittle strength. Same reason we temper metal.

Someone who has been to Canada might go "But I've seen concrete used in building!" and you'd be right -- but that's because of building techniques that aren't available when 3d printing, such as pre-stressed concrete, bubble entrainment, or specially designed spots that are designed to break to protect the rest of the structure.

You're generally correct which is why one technique for making cement last longer in winter conditions is to add air bubbles to the mixture which gives the ice somewhere to go, but another problem is that the Ice can freeze from the outside in, so it creates its own pipe. The ice covering the thing doesn't want to go anywhere so the water turns to ice in the cracks of the cement, and boom! Like a beer left in the freezer.

I saw a video a year or two ago that actually changed my view of the problem entirely.

The thing that's actually difficult about building a house isn't making walls. People built houses out of wood in the forest with nothing but the clothing on their backs and some hand tools, and some of those houses have lasted for centuries. Compare that to a million dollar machine, and a bunch of material that was industrially mined and processed in another million dollar machine.

Meanwhile, the real issue being the engineering, permitting, basement, stuff like insulation, electric, hvac, plumbing, windows, and so on. At the end of the day, creating the walls really isn't a big deal.

Given that, a 3d printed shell doesn't actually fix anything -- and in fact, when people want to live in a storage container, they quickly realize that just because they have four walls and a roof doesn't mean they have a place to live by any stretch of the imagination.

But, I think an angle relating to where you're coming from makes sense -- these are cool technologies with a lot of potential applications, as long as we stop pretending the reason to make cool new building technologies is to magically build cheap houses.