Using the Apollo Automation MSR-1 mmWave CO2 Multisensor to control HVAC fresh air with an Heat z recovery Ventilator (HRV)

I have a brand new home that’s super airtight. After putting in the MSR1 in our main bedroom, I could see that CO2 levels were rising to 1200 ppm and beyond. I had already implemented a simple relay based ESPHome device that closes a set of dry contacts to turn in our fresh air system HRV. By default the builder has the HRV running all the time, but that’s sucking down 100W all the time. I wanted to modify the behavior to run every 20 minutes regardless and the. Shut off. But I wanted to make sure if the outside air is really bad quality over 150 AQI to not bring in that smoky air. I have another ESPHome project for that which has a PM25 and temp sensor outdoors. Now with the MSR-1 I know the CO2 levels, so the automation needs to not shut off the HRV if the CO2 is over 800ppm.

Here’s where my automation lives:

https://github.com/aaronsmorris/HomeAssistant/tree/main/Automations

Here’s the outdoor Pm25 sensor:

https://github.com/aaronsmorris/OutdoorPM25WeatherStation

I’ll add another repo shortly for my HRV controller which is controlling a Broan. You can essentially do something similar in a normal home but instead just firing up fan only on your furnace/hvac system if you have a fresh air intake that is open. Some homes always being in fresh air when the furnace runs with a duct and a simple damper, others have a fancy electric damper that turns on and off with a timer. If you home is built in the last 20 years or so you probably have something. Another option if you can install a simple HRV/ERV in rooms to bring in fresh air and use this kind of automation.

In addition to using the MSR-1 for this automation, I've also used the mmWave radar in it to turn off the lights and ceiling fan in the bedroom if it's daytime and nobody's in the room. This is because the wife likes the fan on while asleep and the mmwave doesn't always think we're there.

Thanks to Cowdog360/Aaron Morris for this post.