Might be able to use a flipper zero as the sensor, if the cats are chipped. Then you'll have data to catch any unusual usage, like a urinary blockage, before it becomes a serious problem! At that point you're a smart switch and Home Assistant script away from fan control.

I would recommend to use an TVOC sensor that detects smell very easily and then automatically switch on a fan. Could be a fun project.

Just need: - TVOC sensor like the SGP41

- ESP32 microcontroller

- Electric Relay

I’m highly unimpressed by my couple of SGP41 sensors, but they would probably work for this application.

Interesting idea. Do TVOC respond with enough signal to low level aromatics verses all the particles from cooking or pollution?

Garply had a blockage once and he did a remarkably good job of communicating the problem to us directly!

As a fellow cat person, I feel pretty confident interpreting what’s being implied here. :-)

Beautiful home and contents, btw! It seems expensive but more than a few folks would have spent the same money on “nicer marble” or something.

Heh, I actively dislike "nice marble" or anything that just looks expensive without providing any functional benefit.

I did wonder where the network connections were going into the cat areas!

Constant fans are sucking outside air into your house. Could be part of your Heat/AC efficiency problem mentioned in your post. A timer to run every 10th minute would be a simple improvement.

A lot of newer building codes require fans to be constantly running anyway due to the other part of the building codes requiring high r-value insulation.

Yeah that's a good point, I should turn off the fans for a day and see if it changes the power use...

Heat exchangers can ensure the incoming air is heated up by the air going out, at no cost.

We do have an ERV. But I suppose the cat fans don't actually exhaust through it. Maybe we could have arranged that had we thought harder about it before construction...

Sir, I want to add that it was deeply inspiring. While I’m struggling at 40 just being a CEO of 14 people, which by one measure is excellent but I have put aside so many lives for it and failed at all my social ventures (yes I mean friends and dates); You, you succeed to have time for a wife (a potentially intellectually interesting person at that, according to your brief summary), you succeed to build a house, manage a lot of people at work, have friends with proper deep connections, and still have energy for home renovations. It’s like you’re living 9 lives at once. Oh yeah and kids. Like my uncle, who, beyond children, still had time for home renovations to build a cozy nest everywhere they lived.

In this day of international men’s day, maybe I should still enquire about your internal mental health, because stress can be discreet, but still, the outer appearance you give from your allocation of time and clarity of mind seems absolutely perfect.

Well I certainly do get stressed sometimes (particularly when cat-herding at work) but overall really can't complain!

BTW it's not a renovation, we build the house from scratch on an empty lot. :)

A sensor would be easy enough, there are simple non-smart sensor fan timer that will activate a fan for a programable time.