Anyone selling house-size CO2 absorbers to keep CO2 in my house to more like pre-industrial 200ppm rather than the 800ppm that's more common of house air in cities?
An actually physically feasible thing you can do is to whitewash some walls. You need to apply about 7kg of whitewash per person per week, so you are going to need a lot of walls, on the order of 400 square meters of wall per person, because the whitewash is regular lime, not soda lime. (If you're daring enough to dope your whitewash with lye, maybe you can get by with less wall area, but you still need to keep applying the whitewash at 7kg per person per week.) You can make them out of plywood, sheetrock, sheet metal, old sheets, whatever whitewash will stick to. After a few months you will need to start throwing out 14kg of fully cured whitewash per person per week, or calcining it to make fresh whitewash. Try to get whitewash with as little chalk in it as possible.
At this small scale, dozens of kilograms per week, you might be able to calcine the used whitewash in a pottery kiln on your patio. Beware that electric kilns generally do not handle reducing atmospheres well. I'm not sure if carbon dioxide would be too much for them. I think it should be fine, but don't blame me if you ruin your Kanthal.
That said, CO2 can often serve as an easily measurable proxy for stuffy air, which can contain particulates, formaldehyde and other organic exhalations which may actually have some effect (psychological, if nothing else). But this just calls for ventilation and air filtering, not CO2 scrubbing.
Offices have high ventilation but also high CO2, and the effect shows clearly in a meeting room, putting people to sleep.
The logistics would be complicated, average plants aren't going to be accumulating so much mass so quickly. You would need aquariums full of algae. Just isn't worth it.
Rooftops nowadays are best used to mount solar panels. Some system growing circulating algae, be it on the roof or on the sun drenched walls while doable would have way higher at least the operating costs. Clining is one thing. If you live in the area with below zero temperatures either you drain the system or invest even more in some glasshouse, maybe thermal isolation at night or heating.
As mentioned by others, there are chemical solutions.
Efficient Direct Air Capture in Industrial Cooling Towers Mediated by Electrochemical CO2 Release
(I'm sure I could do my own research, but was more curious since it seems like you've already got a setup.)
Do you want to use chemicals and devices that make the climate problem worse just to lower the CO2 concentration in your personal space? Sure it’s a small effect but not something we can all do.
Ive had a CO2 sensor for years, take it with me usually. In the beginning I was quite shocked, but I’m starting to doubt all the bad things said about CO2 over 1000-1500 ppm now…
And interestingly there are studies that show that breathing in air up to 3% co2 (30k ppm) "did not substantially impair either cognitive and motor performance" [0]
[0] https://www.tandfonline.com/doi/epdf/10.1080/10803548.2007.1...