Reddit mentions: The best interior & closet doors

Ah, that makes more sense.

So, you could install a small fan in the window to help minimize the sound in the bathroom. Obviously, that won't help with smells, which you probably don't want being blown into the kitchen. Best option that I can think of for the smells is Poopouri spray . It coats the surface of the toilet water with oil, so it traps any smells.

Alternatively, you could install a super-cheap accordion style door on the laundry room, for under $100

Yeah, unfortunately (based on recent experience) that "extra tall" baby gate is still not tall enough.

However, your accordion door comment led me to this which looks like it might be pretty close to what I need. I'll have to measure and do some research, if I don't need to cut the door I think installing it would be within my skill set and from the comments/reviews, I could just add a low bumper on the far side at the bottom to stop the cats from pushing through. Definitely a likely option!

If you have the budget for it, frame out a set of nice interior french doors:

https://www.amazon.com/Pinecroft-830726-Burgundy-Interior-Unfinished/dp/B000ON5WOW

>Career officials ordered the door as “part of the decade-long modernization” of a building that dates to the presidency of Franklin Delano Roosevelt, according to a spokeswoman.

How much has door technology progressed in the past 100 years? It does not need to do much; Twist knob and pull...door opens. Here is the most expensive door I could find on Amazon. Pricey and over the top tackiness at $47,000. I can't imagine what 3 times that would buy you? I can only imagine it is some ultrahigh security door to match his cone of silence room. It's freaking Interior Secretary's office, not a SCIF.

Depending on money, concertina doors?

something like https://www.amazon.com/Closet-Bi-fold-Louver-Plantation-36x80/dp/B00AQ0AI1K

A full louvered door would probably look better than cutting vents into the existing door. You might try that, and see how the temperatures are before adding any fans.

Would the frame take a folding door like this one? We had one on a room in our cabin where a door wasn't possible because the kitchen counter was in the way. Might provide a little more privacy than just a curtain. It may even be possible to "lock" it by rigging something akin to a flip lock, like on hotel room doors, to keep it closed from the inside. Then implement a "no yelling, if you want something you need to come up the stairs and knock" rule that would discourage her running up and down the stairs every 5-10 minutes in the morning.

It's not the most common size, but 26" doors are out there.

https://www.amazon.com/Bifold-6-panel-Hollow-Primed-Textured/dp/B01LX0B360