Aren’t there heat exchanging ventillation systems that do this (maybe even better) without wasting a ton of energy?

We had a good one like that in our previous apartment. They consist of a large cylindrical metal "heat sink" where cold air coming in goes through the bottom half, warm air going out leaves through the top half, and the entire thing rotates at ~ 5 RPM. Not any more noisy than regular kitchen ventilation. But they need to be big, ours was the size of a small dishwasher and that was adequate for a 75 square meter apartment.

Edit: if you are buying such a thing you should get someting oversized, e.g. for a 180 square meter home you should find a unit that is specified for "200 to 350 square meters", not "75 to 200".

Nowadays it seems that simpler Heat Recovery Ventilators are the go-to solution. They're more straightforward crossflow heat exchangers, with no moving parts (except the fans, of course). Energy Recovery Ventilators are also available, built with a permeable interface to retain humidity as well as heat.

No, buy the right size. Those things are better than an open window, but they are still pretty bad from an energy standpoint. Larger ones either run less often, or run leak more energy out of the house.

The state of Montana runs a data center with three 16' 'heat wheels' for the primary cooling. They are pretty cool, if I ever have a large enough hole into my attic space I might get one more appropriately sized like yours.

Yes, but they may not be effective enough; there was a big stink in the area I live where they had houses with a system like that, but the system either didn't have enough capacity, or it had to be cranked up to a point where the noise would be intolerable to the people living there.

I have a one-way system, an air pump that sucks air in through vents and out through the ceiling in a few points; I have it set to the lowest at all times because it produces a constant noise otherwise. We usually have our bedroom windows open and the back door open a crack, it should be fine even if it's not the most energy efficient.

Call me selfish, but I'd like my country to crank up electricity production, reduce its usage by datacenter and industry, and use it to heat or cool houses instead.

I think this is conflating possible fuckups by the developer - like i stalling undersizer or poor quality system- with inherent disadvantages of the technology

Opening a window is free, and not everyone has the freedom to modify their living arrangements(rented houses etc)

Opening a window in winter in Wisconsin is very much not free... It's a classic OPEX vs. CAPEX tradeoff, plus the climate impact (of course building the ventilation system has a climate impact too, so there is a tradeoff there as well).

The one winter I lived in MN I had to open my windows or else the central heating in my apartment would have baked me alive.

In a weird full-circle sort of way, that was (sometimes) the point: it was to allow fresh air to circulate even on very cold days—-and during a pandemic, even.

https://www.bloomberg.com/news/articles/2020-08-05/the-curio...

opening a window for long enough to get CO2 levels down won't likely impact heating bills that much even in cold climates

Yes, these are energy recovery ventilator (ERV) units. They exchange air while keeping both heat and humidity in. They are absolutely critical to health in tight house construction.

I got one too, and a PM2.5 laser sensor. It's a huge challenge during wildfire season to keep the PM2.5 and CO2 both good. Needs filtered HVAC to actually do it. I prefer high CO₂ over high PM2.5 of course.

I need to get into CO2 monitor sales and then some cloud connected device that changes the CO2 levels somehow (maybe just a fan). After that, sell a subscription to adjust the CO2 ppm through a website. People will fiddle with it and pay the subscription for the rest of their lives.