I like 3, have you checked the size limitations from the manufacturer? It would help to see what it looks like on the exterior with that opening and the rest of the house.

Thanks for the feedback Todd. Yes, we did check the window sizes - those are both custom options from Marvin (30 vs. 40). Regarding your question from the outside, that part of the house faces the backyard so won't impact the curb appeal too much either way, but FWIW there is an adjacent room that also has 3 windows (very similar to the one currently in the picture) so we did also think maybe 3 would work better from a symmetry perspective as well...

i think that unless this is the rear of the house, the outside is more important than the inside.

Thanks Ron - we will be putting support studs in between the windows, wouldn't that help prevent issues of sagging?

Good question. The sagging that I'm referring to would be the sash sagging against the frame of the window because its so wide and heavy. That puts a lot of stress on the hardware. If you never open the window maybe not a big deal, but if you like to keep them open a lot, you could run into difficulty cranking them closed after a while.

As far as center supports and the need (or lack thereof) for them, that should really be determined by the header. If its sized right for the span of that width theres no need for any support studs. If not, then yes, I could see why. They should be framed the right way though, extending to the bottom of the wall plate, not just stopping at the rough sill.

Yung kwon

that makes much more sense.

So why not just replace what you have and not interfere with the exterior at all, do you really yhink it is worth the money to have to fix the exterior for a bit more glass. This looks like a DR I would replace the side ones with casements leave the middle . hang some beautiful drapes and be done. Or if it was my space I would do french doors for probably the same cost.

Kwon, I’d probably go to 32 or 30 on the casements. You want the pw to look discernibly bigger. 40 and 36 are too close for my taste. Either go for symmetry or contrasting sizes. Too close but not the same can just look weird

Some manufactures will only make a casement to a maximum of 36". I would advise against going any larger, there is alot of weight pulling on the hardware when its opened.