Is there any kind of CO2 scrubbing that's at all practical for home? I'm curious what the effects would be of going below ambient/outdoor levels, especially since those are rising (if slowly).
I use a relatively small 10x11ft spare bedroom as my home office. If I close the door and window, it'll quickly climb above 1200ppm after 15-30 minutes (and set off an alarm on my sensor). It'll cross 1500ppm easily if left unchecked. HVAC helps but gets outpaced quickly if my apartment windows are all closed.
That said, keeping doors open, running HVAC normally, and cracking a small window open, even 1-2 inches and on the opposite side of my apartment, is enough to keep CO2 levels around 550ppm while sleeping and 700ppm (in occupied rooms) while awake.
A well-sealed, occupied room can build up significant CO2 levels pretty quickly. In my particular case, one person, not exercising, could bring CO2 above 800ppm (reported) in just a few hours.
So I think lack of ventilation causes way, way more excess CO2 than is caused by recent increases in atmospheric CO2. At least in my suburban neighborhood; maybe it's a lot worse in a dense city.
I also couldn't spend thousands on an energy recovery ventilator (ERV) installation because I've been living in rental properties.
My solution was to buy an ERV for ~$500 and rig it up to an open window: https://gen.co/air
I've since moved into a condo with a bedroom with no windows and french glass doors so I installed a cat door and mounted the ERV vents to that.
I think there's a lot of money here for someone to build an ERV designed to be window mounted.
I rent right now, which means I doubt I can, but hoping to buy soonish.
Sounds like something that would be worth it, I spend almost all of my time indoors and we have pets pumping out co2 as well.
TTBOMK, there is nowhere in the US that an HRV or ERV is required by code [1], regardless of the price range. There are a lot of very expensive homes built with no thought to indoor air quality.
In many places in the US, due to higher air-tightness requirements, mechanical ventilation is required, but that can be as minimal as having bath fans and a kitchen extractor fan.
1. Ontario CA requires them on new builds https://www.huskyair.com/blog/newsflash-ontario-is-making-hr.... Maybe Germany also?
https://www.metoffice.gov.uk/about-us/press-office/news/weat...
In the winter the situation is _much_ better, but probably 4 months out of the year, the outdoors are unlivable.
Not scrubbing in the way that a power plant does, but you can improve ventilation, but you probably need to do more than crack a window.
Options from cheapest to most expensive (in upfront cost):
1. Run your stove extractor fan (assuming it is externally vented), and open the window that is furthest from it in the house.
2. Open 2 windows and put a fan in 1 facing out, and if it's winter, wear a sweater.
3. Install a whole house ventilation fan (i.e. Panasonic Whisper Green fan) and keep the furthest away window slightly cracked.
All of the above will cost less upfront but will result in a significant increase in your heating/cooling energy use during hot/cold seasons. If you want to minimize the increase to your heating/cooling energy use, then you need to spend more upfront and:
4. Install a whole house <heat|energy>-recovery-ventilation system. This system brings in fresh air 24/7 while transferring much of the heat/"cold" from the conditioned space to the fresh air from outdoors.
What all of these solutions share is that they don't rely on wind/convection to ventilate the house, they are all mechanical.
The most effective is cross ventilation. I no longer live in places without cross ventilation, it's too hard to air out quickly unless the windows are huge.
It's also good to have windows facing the direction of typical wind direction in whatever geography you're living in.
Or if the temperature is right, just open a window.