I have read the posts on this subject but still don't have an answer.

Can you turn up the fan speed without turning on the air conditioning at all? Sometimes I just want more outside air volume but no AC.

Thanks in advance.

go into the touch screen in climate and turn off the a/c then adjust the fan speed.

jimbosr1 is correct, if you have Navigation just swipe over to the right side of the screen to the
climate icon and tap. You will see A/C in green, tap it off. While you can also change the mode
and fan speed here it is easier to just use the actual hard keys on the dash for them.

Note: when you press the hard key "Auto" you will reengage the A/C. Safety consideration if
when the windows start to fog up you do not have time to open menus and find on screen icons,
punch the Auto button and the A/C comes back on.

thanks for your response however when i shut the ac and then press the fan speed button the ac goes on again. increasing the fan speed turns on the ac, at least in my RX

If you have the AC toggled off (and the Auto hard button is on) and just need to clear some fog off the windows, just press the front defrost hard button on the console which will then illuminate while the Auto button turns off. That should temporarily ramp up the fan and engage the AC - when you don't need to defog just press the front defrost hard button a second time and it should go back to the previous setting (and the Auto button light is back on). This is what I experience on my 2019 RX450h.

Once back to the non-AC operation, adjust the fan speed via the hard buttons (I rarely use the Nav system for climate control ops), though the Auto button should turn back off since you should now be operating in manual mode.