Could this be one of those few situations where a pull-down would actually work better for your requirement?
Well, then I am concerned about the power of my MCU The switch is supposed to work as a pin change interrupt to wake it up from sleep.
Of course, to be most effective, after disconnecting the pullup the pin should be switched to a low output so it does not float or the pin should be disabled.
I don't really see what this would change. With a pull-up, the switch connects to ground, with a pull-down the switch connects to VCC. Same current should flow.
Edit: I just realised you could be in either open or closed for an extended period of time so power "wastage" is a factor in either case. Apologies for not reading correctly.
Hi, for a window sensor, I need a pull-up for a reed switch, to detect if the window is opened or closed. I have already gotten SPDT reed switches, so I can set window-closed state to open. Still windows might be open for a longer period of time, so pull-up current matters. What is the highest "safe value" where my pin isn't effectively floating? Ballpark, of course, safe value without looking into the RF characteristics of the involved traces.
...but that takes more pins.
Another approach is to switch the pullup/pulldown on just before reading the switch, and disabling it afterwards,but that takes more pins.
With double throw switch you may simply connect input to the common pin and any pull-up to one contact and pull-down to the other. No current will ever flow except for filling parasitic capacitances and leakage currents.