I had some issues with the laziness to open window for fresh air (yep, u can be that lazy). Therefore I sought for motivation and found it, by visualize the current humidtiy in collor code of cyan, green, yellow and red. Cyan and green are the good colors. I wrote a short php code to make a simple table (but effective to monitor) which mirrors also the humidity-hue. And by crappy get request in a also simple python script, it uploads the data from my server-laptop (could be rpi, but currently I have no screen (equipment) etc for that) to the webserver.
As you can see in the picture, when you ventilate your room, the humidity goes down by 8% of relative humidty.
I am pondering adding more sophisticated calculaitons but yeah...currently I'm too lazy for that.
Enjoy this project?