This is the great part of the Green New Deal that was shouted down when much of the political establishment mocked it - it would put scores of people to work in jobs in the trades.
The reason for this is that buildings not designed for insulation and air sealing can suffer from dramatically worse durability (mold etc) when just adding insulation. It is not necessarily wise to just add fiberglass batts to wall cavities.
The addition of insulation to our homes is a modern thing, and there have been significant issues even currently (the mold crisis).
The issue is that to build a building properly, it is necessary to address heat flow, vapor flow, air flow, condensation, drying, and water barriers. This means you often have to address the entire envelope of the building, which is very expensive, difficult, and means replacing a lot of material. Basically remove all cladding and sheathing and upgrade it.
Realistically most of these concepts are not well understood in the construction industry, and the expense is high so most corners would be cut leading to huge issues with mold and wood destroying pests down the road.
This is not extremely difficult nor expensive on every building. It's certainly more of a job than cutting holes in the wall on the inside and blowing in insulation. By insulating from the exterior you can address vapor issues. There are benefits: you can avoid having to patch holes (2 per stud bay... ie a lot) and repaint the inside. There's opportunity to upgrade electrical or fix any issues. Siding also has a limited lifetime. Wood siding can be reused.
With some/many buildings it is certainly too hard and expensive, but for many this is not. We shouldn't write off the whole idea because it doesn't apply to all buildings.
But, I don't know how well current codes ensure that all aspects of IAQ are reasonably safe, particularly in residences. I'd need to check, but not sure they seriously address prolonged, elevated exposure to VOCs. I fear that decades from now, we'll learn we harmed a lot of people via prolonged exposure.
US luxuries. I don't think any person I know in Europe lives in a house/apartment with more than 4 bathrooms. I imagine 90% live in one with at most 2 bathrooms.
Did you know that the Romans had under-floor heating.
Conversely, some impoverished people in the US today have very inadequate heating systems in their houses, and resort to things like propane heaters, or running their stoves and ovens to heat the house, which can cause carbon monoxide poisoning indoors.
It’s something which is a luxury in the absence of fossil fuels, or the rollout of new technologies they mention.
The constellation of technologies needed to achieve this efficiently (with far less fossil fuels) and healthily (with healthy internal air quality) exists: heat pumps, heat-recovery-ventilators, airtight but vapor permeable house sealing materials - the standard equipment of passive houses. However, as the article mentions, today it is not available at low cost.
None of this technology is exotic (as in requiring exotic materials or manufacturing processes). It doesn't need to be expensive. Even the labor for installing it in isn't uncommon - air sealing is a DIY project if one is OK with a bit of hard work.
In the US at least, many industries providing these building measures have however reached a kind of equilibrium where they mostly sell it to people of higher means, which makes the global impact of home energy efficiency minimal. Other developed countries - mostly in N Europe - have started putting these into their building codes.
To have any impact, home energy efficiency needs to reach critical mass in the public consciousness, and for that, the public need to start looking at their homes the way that many have started to look at their low MPG ICE vehicles, and demanding higher efficiency both from the private home building market and from regulatory institutions.