First of all, I broadly agree with you, but I'm rolling up to correct a few bits of misinformation and assumption about the US house and town here, because there are a couple.
The Unnatural Key To Better Living I:
While the grid system of urban planning has been around a while, it's also not uniformly enforced at all. Master-planned cities are a new idea, and there are comical failures (Irvine, CA; Celebration, FL), true, but those failures can be learned from and improved. Boston had no plan. Most cities only have spotty implementation of the grid, and many people in urban planning are against grids because allegedly they're "more dangerous to pedestrians" when that assumes a car-dependent culture, and those planners say windy little hard-to-navigate networks of cul-de-sacs are the best way, because they force cars to slow down. But that misses that the problem is the cars, not the grid! The grid makes everything easier for everyone, but it's not the grid alone--you need to consider zoning and let's talk about how suburbs are the worst most unnatural idea ever. Suburbs literally leech off of cities, draining them of resources that should be going back to the city residents. Zoning laws are also to blame for poor results, as they often restrict the wrong things and have loopholes that allow pollution through. I live in a single-residence zoned lot that is right next to a heavy industrial lot and the pollution does not care about the line on the map between our zones!!! I'm also not allowed to work from home as a small business because of my zone. My house is older than the industrial zone, but that doesn't matter. It should but it doesn't, because no planning was done of my exurb at all. Because it's too old and Traditional.
Homes were also not planned until the 1920s unless they were the big aristocratic kind (and sometimes not even then). If you have ever been to Boston, or another old city not built on a grid system like NYC, you will see what a non-planned town is like. It's shit. It's SHIT. There's a reason our ancestors turned toward city-planning and using grids. There's a reason grids exist. The modern city planning you hate is cul-de-sacs and suburbs.
If you walked into my 1903 home you would not comment that it was well-planned, because nothing about this house was planned at all, the working class carpenter who built it just started building. There's not even anywhere to put a kitchen and there is certainly not enough storage, and too much space where space isn't needed. Private homes weren't planned they were just built, often by men, who didn't use the house and therefore didn't usually think to design the house's rooms for ease of cleaning and using--which is why the USDA poured money into their Home Economics Dept researching better and more functional homes--particularly kitchens--in order to ease maintenance and workflow for the people living there, and ease the work burden on the housewife, and then poured money into public education and incentives for people to redesign their shitty old homes to work better.
Planning doesn't happen naturally, people have to learn to do that. Planning a home or a city isn't how things are "traditionally" done at all, and traditional homes are not planned to be easier to maintain. It's a LOT of work to maintain a traditional home; just look up housekeeping manuals and you'll see the long lists of daily, weekly, monthly, and seasonal maintenance. I can tell you my 1903 house expects daily cleaning and dusting, seasonal re-sealing of all wood surfaces, curtains being drawn to keep the sun from shining directly on all the exposed wood, replastering (which is a LOT more work than repairing drywall), re-grouting the tile every 2-5 years, changing out the storm windows for screens and the screens for storms twice a year, repainting, laundering, mopping and waxing floors every week, and on and on and on. Maintaining a house is a full-time fucking job, even and especially in wet snowy Europe.
The Unnatural Key To Better Living II: Easy By Design
You know what kind of house is designed to be easier to maintain and clean? The single-family homes that were designed in the Modern architectural era (1920s-1980s), following the USDA Step-Saving Kitchen research and thinking about homes as homes, where a family lived, worked, and played. Houses before this critical research and attention paid to women and children were built mostly to show off to guests and to follow things that had always been done without thinking about why or whether it was a good idea--the definition of tradition. But the turn of the 20th century and particularly the middle of it saw an attitude of Let's Do Some Research! and Changing Society Into Something New Is Good Actually, and that we should inquire and research into the efficiency of everything, question tradition and make everyone's lives better--and this went all over the place. This overall attitude went toward how people argued, how they became active for the betterment of their communities whether that meant treating housework as work and subjecting it to efficiency and ergonomic research, or pooling resources and becoming politically active to defend the human rights of all people in the community, not just the whites, straights, and/or men.
Thatch roofs and one-room cottages with tiny windows and huge but undesigned kitchens where appliances and counters are shoved willy-nilly that are full of bug-covered plants are not efficient, sanitary, or pleasant to live in. Just ask any given European who is stuck living in one of them, you'll hear complaints. Cottagecore is an aesthetic that only works in daydreams and staged photographs. It isn't real. Solarpunk is meant to be real and functional. If you want an aesthetic for that, you'll have to--as you, Chumb, have said--put more research and thought into the climate and local materials.
False Solarpunk: Green May Not Be
Here's a smial-like home that might be good in some climates but not others:
This is a Modern home plan, probably from the 1970s, and looks awfully Solarpunk from the first, but... this home would be a Bad Idea in the summer, because the windows are all in the same side of the house and therefore the house would get stuffy quickly, and there would be no breeze coming in here, ever. And while some older houses did account for their climate--I've been in a lovely Victorian that is so well-designed that it doesn't need air conditioning even in the middle of Southern California on a hill, because if you open all the windows a breeze spirals from ground floor to roof constantly--they required a planner, an architect, who actually cared and had knowledge of such things.
So, things that SEEM environmental... sometimes aren't. LEDs are VERY greenwashed while being absolutely not. The only thing LEDs are is less of a fire hazard--but they're a MAJOR health hazard and environmental hazard because of their flicker and narrow-band blue light, which is one step beneath an actual laser! Induction lighting--i.e. neon, sodium, and fluorescent--is actually the choice that is "greenest", because it lasts the longest and we can now make it without using mercury at all. Even Incandescents, absent planned obsolescence, can last for over a century! The problem is, yes, capitalism! The problem is planned obsolescence! The problem is "oh only 1% of people notice health problems from LEDs they don't deserve to be accounted for" the problem is "well brighter is ALWAYS better".
And this is true of solarpunk as well! True solarpunk wouldn't have green roofs, they'd have locale-dependant materials: metal ones in the snowy places--metal lasts the longest of all roofing materials, and is good in all weathers, highly resistant to the freeze-thaw cycle. Clay might be best for drier and hotter climates without a freeze, there's a reason it's everywhere in those areas. You don't want to put plants--which need moisture--on a building, which needs you to protect it from moisture. You just need to plant more plants on the ground, where plants actually belong and are happiest.
Traditional Or Modern? No, A Secret Third Thing: Practicality
And that's really the whole point--the pivotal point is not about Tradition Is Good, Modern Is Bad, it's about Research And Cognizance Of The Site and Residents' Needs Is Good, Thoughtless Cookie-Cutter Cost-Cutting Design Is Bad.
You take historical techniques into account, but you do not prioritize them over what works and what is needed for THIS site, for THIS town, for THESE resources and weather and for THIS family who will be living in it. And that's also something I think a lot of people who have always rented and been transient from year to year have difficulty understanding or thinking about, is the idea of a house being built for a family that will be there for their whole lives.
Building with local materials is something you can find in every modern home with very few exceptions: Stucco is very common in Southern California, as common there as brick is rare, and in homes built anywhere from 3000 BC to 2019 AD, individually or in tracts in suburbs, because stucco is cheap. You know what stucco IS? MUD! People still use the cheapest local material to build things with, that hasn't changed much. But maintenance has gotten cheaper and safer: drywall is much easier to maintain and repair and build with than traditional lath-and-plaster, believe you me, and modern shingles are made of fire-resistant material that is less toxic and messy to the roofers than materials from the past. We no longer use asbestos, lead paint, and aluminum wiring for a reason.
In a warming world we need to fight the warming of course, but we also need to look to the hot places for what materials they use, what styles they use, to keep their homes cool. Soaring high ceilings and clerestory windows are a much-loved feature in atomic midcentury homes all over Palm Desert for a reason. Breezeways are a common feature for a reason. Deep eaves are a feature for a reason. These are not "traditional" features at all, the Indigenous buildings in deserts are mud-daub and have tiny windows, and while they are somewhat subterranean to take advantage of the coolth that provides, there are also modern ways to build cool houses that make use of that mud-daub (stucco is a form of mud!) and subterranean (sunken living rooms and conversation pits!) techniques. You prioritize what WORKS, not favouring anything without questioning and studying it.
A Final Warning: Against Nostalgia
But anyway, my point is, solarpunk isn't just "not about" cottagecore, it's actively supposed to be the opposite of cottagecore. Cottagecore has inherently got ties to fascism by its very nature as a retrogressive nostalgia (I would argue that nostalgia has ties to fascism bc fascism is about "the past was better" but the past is falsified), Solarpunk is meant to be directly about that 20th century attitude that The Future Will Be Better Than The Past Because We Will Make It So Together.
It's rare it is that the future is looked upon with optimism, these days; but it is very, very common to only look backwards and say you long for the past and the future is not going to be at all. However, that's the depression of the zeitgeist talking. Don't listen, depression is a liar.
Do NOT fall into the nostalgia trap. Nostalgia is bad for you, it's a form of pain. You need to study the past, study all things, in order to make the home of tomorrow; but not dwell on the past or hold it above the present. If your home has mud walls, let it be because you researched all materials and possibilities and observed that mud walls are the best choice for that house, in that location, that meets the needs of the residents. Not because it's Tradition. I've seen that video too, and the point she makes is that she knows the reasons mud-daub is a good building choice for her resources and needs and weather, NOT that it's tradition and tradition is better than modernity.
America's Housekeeping Book, 1934
Planning the Efficient Kitchen, Ex. Bulletin 247, 1939, from WSU's agricultural dept.
Archive.org's 1920-2000 home plan catalog archive (many catalogues)
Better Homes and Gardens 1960 catalog of homes
The USDA Step-Saving Kitchen
The LED Debacle from Softlights.org