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Comment by smileysteve | Hacker News Reader

The cheap DIY is to add WiFi switches to your bathroom fans, turn them on when humidity is lower outside or when the outside is cooler than the inside.

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WiFi? Eh. As an ever-so-modest upgrade to the cheap DIY, a Zwave or Zigbee system might be a better choice to integrate with a variety of other things (like thermostats and temperature/humidity sensors.)

Wi-Fi is easier to interface with using any computer, where as those other protocols require a dongle on the computer side.

Sure, but once you have 20 or 30 of those things in your walls, congesting up your network, you’ll wish you went with something that runs at 900 mhz.

>20 or 30.

In my house. 9 X main lights. Kitchen work lights. Extractor fan. Oven Hob (gas) Dishwasher Washing machine Dryer. Fridge. Freezer. Food processor Kettle Toaster. TV. Digi box PlayStation (2 but anyway) Extractor fan Boiler Laptop Printer 5 X lamps.

So I managed to get to 30 things. I'm not entirely sure I'd want to hook up all those things to a network though...

Zigbee also runs on 2.4GHz, but I wouldn't even count WiFi out just yet since those devices are on 2.4GHz where latency and throughput are almost irrelevant (to me) for that application. Plus it's usually cheaper.

The problem is that lots of little wifi devices on your network will slow down everything where latency and throughput is relevant. I guess WiFi 6 will "fix" this, so maybe I'll be wrong when light switches are all WiFi 6, but I'm right for now.

Also, latency is very relevant for IoT stuff. Lights turning off 2 seconds after you push a button is a crappy experience.

Most WiFi switches are based on ESP chips. Meaning they are trivial to install custom firmware on to extend the functionality. I haven’t found any affordable Zigbee or Zwave switches of this kind. Meaning that all the smarts need to be programmed centrally instead of putting them locally on the switch itself.

Or use a cheap zigbee or zwave power plug to switch the fan, then run the logic somewhere else. (I do this)

Presumably you're doing this to pull in air from the outside using negative pressure? I heard this approach isn't optimal because negative pressure means that you'll be pulling in air through the various gaps/crevices in the walls, which is dirty and might have contaminants like mold.

This should not be done because it will draw outside air through the walls of the home leading to moisture problems.

Doesn't this warning then suggest that bathroom ventilation fans should never be used? And should be removed from houses (and building codes) at all expediency?

Yup but no. Bathroom fans are never on continuously.

A better solution is to open one window on each floor in addition to turning on the exhaust.

The suggestion isn't to turn them on continuously (as this would also wear the motor) but in situations that are similar to that of when showering (high humidity or temperature)

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