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).
By far the simplest solution is to just crack a window. Even a modest amount of fresh air exchange is enough to offset most of the CO2 generated by the people inside.
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.
From some (personal) research I did several years ago, I think good ventilation is by far the biggest concern.
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.
My issue with that is that in the summer, ventilation is ~impossible. It's 110 degrees out there, reasonable ventilation would mean either burning out my A/C or living with temps that are far too high.
Simplest solution is a high efficiency air to air heat exchanger to let you circulate a lot of outside air. They are less efficient when dealing with high humidity, but you can have this as part of your HVAC system and never really think about it.
If you do this (install an HRV), expect it to cost many thousands, and make sure all your duct-work is running through very well insulated spaces, or you will obviate the heat recovery part, and you will just have a very expensive ventilator.
Yeah, I'd assume it'd have to wait until I'm going to replace an hvac system anyway. But in my price-range of homes, that's fairly likely to be ~required anyway.
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.
> Is there any kind of CO2 scrubbing that's at all practical for home?
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.
You wouldn’t scrub the CO2. You would use an Energy Recovery Ventilator or Heat Recovery Ventilator to supply fresh air without impacting air conditioning too much.
Or if the temperature is right, just open a window.
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.