Mini split + ductless ERV [1] would probably be cost efficient and effective for this home office. No need to get a full ducted hvac setup.
reply[1] e.g. https://www.pioneerminisplit.com/products/pioneer-ecoasis-50...
There isn't really any clinical evidence for CO2 levels impacting stuff beyond so called "sleep efficiency," where the effect is small (above 1000 ppm is 5% reduction in sleep efficiency) and it has the counterintuitive effect that less efficient sleep is sleeping longer, which is usually what people want. That said, placebo effects are still real.
replyhttps://newscenter.lbl.gov/2012/10/17/elevated-indoor-carbon...
replyYou are wrong about the impact of moderately high CO2 levels.
i'm aware of this one. clinical evidence - do moderately high CO2 levels CAUSE a disease? afaik no. the test in this study: they measure something real, but it is not used to diagnose someone routinely (despite what they say). they had a surprising result where performance on one of the subtests increased, and some were not affected (see https://pubmed.ncbi.nlm.nih.gov/23008272/#&gid=article-figur...). i am basically saying that, CO2 levels - do they cause headaches like the user is saying? I don't know, nobody has investigated that. 2500 ppm is very high concentration. it merits more study but not a panic.
replyIt might be that poor ventilation gives me headaches for other reasons, and CO2 concentration is just a useful proxy that's easy to measure. The evidence seems to support this idea, whereas like you said the evidence for CO2 in isolation is pretty questionable.
replyIf nothing else, at least a well-ventilated room expels my farts and other airborne waste products.
And people don't want to sleep longer, they want to feel well-rested. So I think higher sleep efficiency is better.