For instance are there any neat filtration systems I can install in wall cavities? I'm also trying to be mindful of soundproofing but am willing to make tradeoffs.
For instance are there any neat filtration systems I can install in wall cavities? I'm also trying to be mindful of soundproofing but am willing to make tradeoffs.
Some things to consider:
This is also a good time to make your house well-insulated, like a "passive house". To ensue good air quality when all the windows are closed, you'll want an air filtration and ventilation system, ideally ductwork that cycles air through the house. Even if you weren't planning on the insulation part of things, the ventilation strategy required for that kind of design promotes the highest air quality because it tackles the problem of, "how do we keep the air filtered, circulated, and dehumididied?"
If this is too expensive, you can implement the basic parts of the strategy on a per-room basis. Ventilate to/from the outdoors with fan systems with replaceable filters. Use a dehumidifier system. Keep your heating system clean or filtered so that heat isn't burning dust.
Don't use natural gas for anything. It doesn't burn completely and the byproducts are bad for air quality.
The worst air quality rooms are bathrooms if humidity isn't controlled (leading to mold) and kitchens because there is inevitably combustion there even without gas. It's good to have windows and a very powerful fan system by your stove. Something much more powerful than the usual hoods. Like the kind people use for home cooking in woks. Ideally cook outside as much as you can. If you can add a semi-outdoor kitchen that's the best.
Get the best wall siding (e.g. sheetrock) for your climate. Certain kinds are better against mold than others.
If you have any existing ventilation systems that you plan on keeping use this opportunity to clean them and put filters on them so you don't need to clean them again.