I like the 1/4 - 1/2 - 1/4 arrangement myself. Makes the room feel bigger. I would go without grids if this were my home and that will open up the space and make you feel more connected to the exterior which is beautiful in this case.

A 3-Lite slider would work here as well as a Double Hung - Picture - Double Hung combo.

If you have vinyl now, I would suggest you look at some of the nice vinyl lines that are out there (Soft-Lite, Okna, Sunrise) and see what you can find. They are all going to be better performers than what you have there or any of the wood products you quoted. They are available with split finishes so you can get them painted on the exterior.

Great advice above. A premium vinyl product is going to be your best bet to blend with the other existing windows and deliver on great performance as well. I'd also agree on the brands recommended above... Seems weird that Okna would not service your area given that they are based in PA. Did you contact them directly for a referral?

I'd also concur on the dh/pw/dh arrangement offering the superior performance in that size, and that this really is NOT a DIY job. Large and/or mulled units can be tricky, and you also want a thorough understanding of general construction and flashing/water management to ensure a proper install... Perhaps you have some experience, but if not, this would not be the best place to "give 'er a shot" IMO.

Thank you for the comments Ultra Windows! I haven't had any dealers tell me to be wary of the slider option, so I need to start asking that question. Do you think I'd be asking for trouble with this configuration even with a manufacturer like Sunrise or Soft-lite? I can't do casements, as the window overlooks our deck and they'd be too easy to run into when opened. I have nothing against the double-hung option stylewise, but in addition to being more expensive since it would have to be built as three separate pieces the stiles have to be thicker. I thought the slider would maximize my viewing area.

I'm still struggling to understand what standards I should be most interested in with my setup, but I will continue my research in that area. Thanks for checking the Vinylmax website for me! I'm really hoping the Soft-lite dealer I meet on Thursday will wow me. I am uncomfortable with the Sunrise dealer, as he really didn't want me to buy their window. I wonder if they get a better margin on the less expensive product?

I was definitely not thinking DIY, but I was surprised the dealer would indicate install was such a breeze. This dealer could get additional business by helping me contract out the install to one of their people...he indicated the cost would be $350. So these dealers are confusing me, as their information and feedback seems to be at odds with what I'm learning here.

And thank you too HomeSealed Exteriors! I'm glad to have another professional opinion. I did call Okna directly, and they told me no go. I was surprised as well, but they are on the other side of the state.

Couple things:

I think that a slider is viable, although just not ideal, and for the reasons that you mentioned (lower cost, more glass, etc). It would be ESSENTIAL, however, to get an excellent product and installation for that option. Even at that, it would not structurally be as strong as a mulled triple unit.

Regarding the different information being given, the advice that you receive here is as objective as possible. None of us have anything to gain by providing it, while that may not be the case for the others. In addition, you are talking to 3 guys here in myself, Ultra, and WOW that are true window geeks with extensive experience in product, installation, etc . Wouldn't be posting to help random strangers if we weren't... A guy at a supply house? Who knows. Take it for what it's worth ;)

I agree with everything HomeSealed has said. A 3 lite slider is doable, it's just not ideal for me. I understand that it is a cheaper option, but I just doubt you'd be happy with it over the long term.

I met with the Soft-lite dealer today in my house, and was
overall left with a positive impression.
Like the pros on this board, he thought that the DH-P-DH option was
preferable to the slider from a structural perspective, but that a slider was a
viable choice too. His firm handles the
labor too, which assuming his references check out is a plus for me. A few questions/concerns…he quoted me on the
Soft-lite Element series, but he said that Soft-lite private labels these
windows for him with another brand name (Timeless). He
said the only difference between his privately labeled Timeless windows &
Soft-lite Elements was the tilt mechanism, as he does not like to have the tilt
latches built inside the frame like on the Elements. On his Soft-lite Timeless windows the tilt
latches are flanking the locking mechanism.
He quoted me a U-factor of 0.27 and and S-factor of 0.27 for the Timeless
product. He did not feel triple
insulating glass was worth the upcharge.

Any additional opinions on the Element series in general, his
private labelling, and the numbers on the product he quoted? Thanks so much for all your time, as I move
close to a decision. Price-wise, the Soft-lite quotes came in a little less than the Sunrise dealer when I include labor costs.

Can't go wrong with the Element window. Solid performer and very well structured.

That's a weird response. That window is a new construction, vinyl, mulled unit. No reason that you can't use a replacement option there. If he/she can't recognize that, I suggest that you look for another contractor.

i am following this thread because it is very informative and interest to see the choice price and out come of your project..all my windows are bad, old home. Time for me to start learning and saving $ to replace.