> I would not want to live in a city where I have to be careful letting in outside air or going outside because there's too much air pollution...

1. Not living in a city (polluted or otherwise) still does not solve the problem of letting out cooled air and letting in hot-humid air in the summer, and letting out warmed air and letting in cold air in the winter. If your CO2 is high are you going to crack open a window when it's -10 outside? Or in the middle of a heat wave (esp. if you have AC and paid to run it to cool your house).

2. Not-city living also has pollen and other allergen leakage. You're also more likely to get wild fire particulates in less urban areas.

Building tight and ventilating right is applicable in all locations and all climates.

And in the extreme case, if you believe the outside is the healthiest environment, live in a tent or under a tarp. :) Buildings were invented to have a separate outside and inside, and leaky houses reduce the effectiveness of that separation.

Even if you live in an air quality paradise, it’s not ideal for your indoor air to be the air that manages to sneak through all the little cracks in your structure. Especially if you have cold outdoor temperatures, indoor humidity such that the outdoor temperatures are below the indoor dew point, and airflow through the walls that can lead to condensation and possibly mold in those walls.

Your indoor air should enter through windows or intentional intakes, not incidental gaps.

Living in the countryside won't save you. I spent my childhood in a rural area and our house had the misfortune of being situated on a steep hill, so at all hours of the day and night you'd have cars and motorcycles and tractor trailers revving their engine to get up that hill. Every year we'd have to powerwash that road-facing side of the house to clean off the accumulated black grime, and sleeping with my window open, which faced that same road, always caused me to wake up raspy and hacking. Cars are a problem no matter where you live.

> Not everywhere is LA.

> How much does implementing all that cost? What degree of benefit does it offer over simple window in situations where those concerns are negligible? What other benefits to human life could be procured with that money?

Everywhere not being LA is actually an argument for ERVs/HRVs. The weather in LA (AIUI) is fairly even and consistent and it is probably fairly easy to just open a window.

But if you're in Texas with high humidity, or Arizona with high heat, or north of the Mason-Dixon line where people get winter, it's kind of hard to open a window when it's 0 or -10 outside. If you have stale air (perhaps as measured by high CO2) what are you supposed to do?

Over the July 4, 2026, weekend it's supposed to get >90F/>32C on the east coast of the US: do you want to open your windows and let all of that heat in? Especially if you already have an AC unit so paid to run it get your home's inside temperature down?

If you have a place with ducts, you can purchase an ERV and tap into that for US$ 1000:

* https://www.hvacquick.com/products/residential/HRVs-and-ERVs...

or even less:

* https://hvacdirect.com/air-cleaning/erv-air-exchangers.html

And even in milder climates (like LA), have the ERV suck in air from the outside through an MERV 13(+) carbon filter, and not only do you deal with things like wild fire smoke, but wild fire smell:

* https://www.greenbuildermedia.com/blog/wildfires-make-indoor...

* https://shop.aprilaire.com/products/aprilaire-513cbn-odor-re...

It is possible to make your indoor air cleaner than the air outside.