ᐅ Bathroom extractor fans – What capacity is needed?

I have read that a bathroom exhaust fan should replace the room air 6 to 8 times per hour.
To be on the safe side, I calculated for my bathroom:
3.5 x 3 x 2.5 = 26.25 cubic meters (m³) = 25m³ x 8 = 200m³ fan capacity.

Now... a fan with that capacity doesn’t seem to be very common. At least, most are apparently smaller.
Also, showering typically takes about 10 to 20 minutes, maybe a bit more, and bathing about 30 minutes.
Do I really need a 200m³ fan then? Probably not?

The larger fans I’ve found have a capacity of 150m³. Wouldn’t that be enough?

I’m not sure if I’m overthinking this... I have an exposed roof truss that should remain untreated, so I don’t want to take any risks there. But maybe that’s an advantage because the wood can absorb some moisture and slowly release it again?

How well do these humidity sensors actually work? I would probably set mine to 60 or 65% to prevent mold and damp spots on the wall and wood.

I would rather avoid connecting the fan to the light switch. It’s better to have a separate switch that starts the overrun timer or keeps the fan running until you switch it off manually.
Basically, I would fully rely on the sensor anyway, since that’s the most convenient option.

What kind of fans do you have in your bathrooms? I’m surely not the only one with a 10m² (107.6 sq ft) floor area and about 2.5m (8.2 ft) ceiling height.

Edit: Many fans also only have an overrun time of about 20 minutes. That would mean a 150m³ fan exchanges 50m³ of air in 20 minutes, which is just twice the room volume—far from 6 or even 8 times air exchange.

So somehow none of this seems to add up...
If the fan runs for 20 minutes and is supposed to exchange 8 times the air during that time (while the remaining 40 minutes of the hour have “no” exchange), then I would actually need a 750m³ fan...
Off the top of my head, I don’t think even a kitchen range hood exhaust has that capacity.

I can't imagine where you read that – which is probably why you can't find any fans like that.

Such air exchange rates are typical for entire houses...

In our 12m² (130 square feet) bathroom, the air exchange rate at nominal ventilation is about 40m³ (1413 cubic feet) – and this is a calculated value from the planning phase related to moisture protection.

I have no idea how much air exchange my fan provides; I should check that sometime. The fan itself turns on automatically at a certain humidity level, and I also have a manual control (a rotary switch that can be set anywhere from 0 to 15 minutes and then counts down, like a kitchen timer).

My range hood has an airflow of 600m³ (21,190 ft³) on the highest setting. Maybe something like that above the toilet could be an option.

I find that idea interesting. I would also consider combining it with the toilet lid as a switch.

Even Punkt de writes it

ventilation experts also write it

you really see it quite often.

I still stand by it... range hood.