You can achieve this with a sensor like this: http://m.co2meter.com/?url=http%3A%2F%2Fwww.co2meter.com%2Fblogs%2Fnews%2F128721927-co2-meter-helps-lower-heating-costs-for-business&utm_referrer=#2428
…combined with a Mimolite using its inputs. We’re doing this old school right now (the Co2 sensor is connected to HRV dry contacts) however I also use the mimolites to operate and monitor status of our building windows.
The sensor needs to be powered by the 24volt output on your furnace. Mimolite is powered by a wall wart…so you can install this in your furnace room. Use the Mimolite input in ST to trigger your HRV. I manage a second HRV with a simple AEON switch which monitors occupancy vs inside (ecobee) and outside (weather underground) temps.
If you read the blog post done by Co2 meter (I have no connection with them) you’ll see that the HRV often does not have to run at all, particularly on windy days.
My staff likes the Tongy unit as the LEDs on the front signal Co2 levels and also allow manual override. It’s been dead reliable too.
I’d be stunned and amazed if ecobee or similar does not integrate a Co2/moisture sensor into their system. It’s a niche that is open right now in the HVAC market. A lot of power and BTUs get wasted running HRVs. On the other side, my older home with four occupants was hitting 1700ppm CO2 regularly. Suggested levels are 600-700ppm. Outside air is about 450 ppm. Adding a self contained Panasonic ERV fixed this. I control this unit via ST and a Zwave switch for power. I use the LFM20 to toggle high/low speed based on our occupancy.
This thread is my review on the small Panasonic ERV controlled with ST: http://www.garagejournal.com/forum/showthread.php?t=322725