I've had a 2 lite Marvin Glider Wood Interior / Aluminum Clad Exterior for 25 years in my kitchen. No leaking. I think it's always nice to be able to get fresh air into a room.

Another option that also seals tightly and which opens without that center stile would be a hopper window (hinge at the top, cranks opens outward at the bottom). It would have the effect of the picture window but will be able to open. I just don't know if they make windows that large in the hopper style. I got this type of window in my bathroom. They are not allowed in bedrooms, but are okay for the bathroom.

Slider would be practical. What window treatment were you considering?

How will it look from the outside? How will you address privacy? If you use film or shutters then I would select a picture window.

do you need to open the window? I have a window (casement) in mine and open it when the shower is running. I do not have a fan.

If you have a fan and will be relying on that for steam venting, then do a picture window.

if you want to open it, I say do a french casement type of window instead of these cheap looking vinyl sliders.

There are lots of slider/glider windows that aren't cheap looking or made of vinyl.

French casements are lovely but if they open out, you have the screen on the inside, which many don't like. And if they open in, you need the clearance on the inside for the sashes to swing in.

Thank you to all who have responded so far! Here are the answers to some of your questions:

1) We do not have any other windows in this room. There was another small, awkwardly placed octagon window near the shower and toilet, but we are actually going to get it bricked up to allow for better flow of the room.

2) We have pretty typical Midwest climate-hot summers and cold winters.

3) We had looked into a hopper window at one point, but as some mentioned, it wasn't going to be economical or easy to find that large of a size in the hopper style.

4) I haven't even though about window treatments yet! I probably should, but there have been so many other details we have been sorting through.

5) This bathroom is in the back of the house on the second story. The rest of our windows are square or rectangular so I think this change will actually make the back of the house appear more symmetrical. We aren't too concerned about privacy as we are on a private lot with no other houses in view from the bathroom.

We appreciate all the questions that have helped us think through what might be the best decision moving forward. I am very excited to see how this project will transform the space.

I would want windows that open but not a sliding glass door...hold on... you mean a sliding WINDOW? Yrs by all means something that opens in EVERY room. Just not a door behind your tub. Casements would be my preference. Or match the other windows in the house.