Hi, folks! I've been lurking on this forum for some time without a membership because my Efficiency Kansas certification ran out years ago and I never pursued other certification. I haven't done a full energy audit myself in years, but I try to stay current with the field, so thank you for letting me lurk.
After doing a bunch of air sealing and insulation in my previous house in Kansas, I was concerned the house might be too tight, so I bought a uHoo air quality monitor (uhooair.com) which monitors temperature, humidity, air pressure, CO, CO2, TVOCs, particulates, NO2, and ozone. It found nothing interesting in that house (aside from raising a red alert when I once brought home a ripe cantaloupe!), so I had it in my in-laws' house for a year or so, but without any control over the situation there, I learned to ignore it.
When we moved to Omaha last year, I put the uHoo in the bedroom of our drafty 100-year-old apartment, and immediately it started freaking out about TVOCs and CO2 spiking each night when my wife and I and our two dogs would come into the bedroom. Whenever we would leave the room in the morning, these two factors would go back to baseline levels (below 400 ppb for TVOC and around 400 ppm for CO2). So we had met the enemy and it was us, but we figured when we moved to a house and had more space, that would resolve.
So we moved to our 95 year old house in June, and initially I put the uHoo in the finished attic because it smelled like dust and varnish to me up there, and I was curious about the particulates and VOCs. But it was unimpressed by the particulates; it continued to detect spikes in TVOC (as high as 1200 ppb) and CO2 (regularly 1000 but as high as 1800 ppm) every evening around the time my wife got home from work (I work from home) and every morning when we wake up, in spite of being sealed upstairs with no ductwork connecting it to downstairs.
I had a local energy auditor come and check the place over; he found plenty of air leakage and suggested that maybe the water heater was venting into the attic (brilliant!), so I had that checked out, but no, it is not. A friend suggested nocturnal animals might be living in the attic, but there's been no evidence to back that up. After a few more weeks of puzzling over the data from upstairs, I moved the uHoo to the living room, where I work during the day. Now it's showing high CO2 and sometimes TVOC all day long, as long as I'm in the house. As soon as all people leave the house, even if the dogs and cat are still here, the CO2 goes back toward baseline. If we go away for a weekend, the CO2 stays low until we return. The presence and absence of people in the house seems to be the one consistent factor in these readings.
Now, the alerts that I get from the monitor say I should open windows or add ventilation, but the energy auditor says the house is too leaky to benefit from ventilation and I should seal existing leaks first. I'm hesitant to seal any leaks when I'm already swimming in CO2. I've experimented with opening windows when it's not too hot out, but while that gets the CO2 under control, it lets in a ton of humidity that the AC won't remove unless I turn the thermostat way down.
I'm curious to know what you think about this situation. What am I missing?