I built a new house last year and moved in this January. This is my first time living in a house that’s air tight enough to have an air exchanger. Through the winter it was fine - I just left it run its own Eco mode and everything seemed good. I’m finding spring really frustrating though - most days are nice and warm and we open windows, most nights are cool and we close the windows. I don’t like wasting electricity by running the air exchanger all day when the windows are open.
I’ve considered window sensors and a smart plug on the air exchanger, but I don’t really want to install 13 window sensors.
Are there air quality sensors that are accurate, and reliable, enough for me to turn the air exchanger on whenever the CO2, or whatever it is that make a house feel stuffy, level gets high enough?
My air exchanger is a very basic “builder” model and won’t do this itself. It has an air quality sensor and changes the fan level to what it thinks we need, but it won’t turn off when we don’t need it.
This is absolutely doable. I have ours setup to turn on when co2 roses above 800ppm and then turns off when it goes under 650ppm. I choose those numbers somewhat arbitrarily but they seem to be good enough.
There are plenty of sensors out there you can use. My sensor is an iqair visual, but that is just what I had on hand when I went down this path – if starting from scratch I would probably look for a cheaper CO2 only sensor.
Not exactly the same, but I have an air quality sensor I use to turn the HVAC fan mode on/off to filter. Also a CO2 sensor. Both wired to the RPi I run homeassistant on. The HVAC is controlled via T6 pro Z-wave now, but I started out with a Zooz Zen15 switch to just turn the whole thing on/off.
The CO2 sensor has been pretty stable for 4(?) years - it has an internal recalibration routine that resets its baseline based on the past week’s data. My readings range from 400-ish with the windows open & fans to 1200+ cooking with gas in the sealed house. Averages around 800 with the AC or 500 with the furnace (which exhausts combustion gasses). The aq sensor has been replaced once after 3-4(?) years. It reads exactly what purpleair says is outside with the windows open, drops to 0-2 µg/m3 with the filters running, spikes to 300+ cooking.
IKEA window sensors are pretty cheap, and that’s what I’ve used. You’d need to have a lot of sensors or a lot of faith in the rapidity of air movement to avoid window sensors.
If you have a couple of favorite go-to windows, you could just put sensors on them and eat the delta cost in efficiency.
Zigbee door/window sensors are like €3 on AliExpress. They are easy to install and work fine imho.
I use a Shelly to control the fresh air intake based on indoor air quality and outside air humidity.
