I have done many experiments with Co2 to date… And I can tell you it is the hardest perimeter to efficient control… Everything else super easy…
If you want to take full advantage of Co2 you need some powerful lighting… (without this Co2 will not do much for you)
I was pushing 2 630 Watt LED in my tent running temps 85 to 90… I pushed the plants with 1200 Par / ppfd. I found this to be a bit on the strong side 1100 seemed better… I’m not sure how much info you want here but fell free to ask me any questions on Co2.
If I was in your shoes and my house is 1000 to 1100 ppm I would put a control in place when Co2 drops to say 900ppm turn on a intake fan to increase your co2 level back to 1000 to 1100… (take air from house )
You are correct plants don’t Photosynthesize without light so no co2 is absorbed by the plant with the lights are off…
I never had luck with Exhale Bags… You want to play the co2 game only 2 ways (my opinion) get you self a co2 regulator and tank… Or a Co2 generator both ways have there advantages and disadvantages
Generally speaking here are the correct light levels for each stage:
• Seedlings or clones which are newly sprouted or planted: 100 umols/ms PPFD +/- 20
• Rooted clones/young veg plants: 250 umols/ms PPFD +/- 50
• Vigorous veg plants: 350 umols/ms PPFD +/- 50
• Vigorous veg plants:(supplemental CO2 of 1200ppm+) 550 umols/ms PPFD +/- 50
• Reproductive/flowering plants (not using supplemental CO2): 750 umols/ms PPFD +/- 100
• Reproductive/flowering plants (supplemental CO2 of 1200ppm+): 1000 umols/ms +/1 100
One more thing to add alot of people think to only use co2 in Flower but done correctly in Veg you can build a rock star plant