My own "redesign" is just to look at how homes used to work. Wattle and daub, hogan, pueblo, timber frame, log cabin, long house, clochán, crannog, igloo, walpini, adobe, brick. They each have pros and cons, but they work best for where they were built and the needs of the people that lived there. They adapted solutions for heating/cooling, pest control, weather resistance, cooking, storage, etc that fit their purpose. As far as I know, none of these homes ever had to deal with annoyances like mold or carbon monoxide. But then again the downsides could be severe in densely-populated urban areas; entire cities could be razed overnight by fire and strong winds!

Before modern homes were redesigned to take advantage of supply chain efficiencies, timber frame and stone foundation were common in the US. Before air conditioning, homes were designed for where they sat to take the seasons into account. A central corridor of air could be funneled by opening doors or windows on either side of the house, rapidly cooling or heating it, and windows and shutters could lock in whatever the temperature was - but this would be a bad idea on a humid day! A stone foundation acted as a mini thermal battery, and some building materials were incredibly good insulators. Also common were fireplaces and living quarters in the center of the home; shut all the doors to keep your room toasty warm, or open them up to warm the house for company. There was no vapor barrier, no sheeting; just nail some shingles to the frame and stuff whatever you can into the walls for insulation, or build walls out of a composite like mud and stick. In wet, hot areas, you had lots of porches and big awnings so you could stay outside with a fan in the shade.

There's many other old-school techniques we could be using, but then homes become more expensive as no contractor knows how to build them, or we've literally done away with all the natural resources and now they have to be acquired at great expense. Not to mention of course, zoning might have made it all illegal anyway. In many ways we've engineered ourselves into a corner.