i will tell you this.. Okna 's mid line windiw ( 500 series ) has a Total Ufactor of .25 in double pane glass with argon and a .19 with triple pane argon.
right there that makes a rather big statement. further, the okna 500 air leakage rate is only a .02 which is phenominal. so clearly this is not an apples to apples comparison. interstate is an ok window but okna will be on another level of performance.

i just noticed the pricing for Interstate.. that price is WITHOUT INSTALLATION..

mmarse1 is correct, it is a average window at the best and your definitely not getting anything comparable to either Andersen 400's or pretty much and Okna product.

Wow....Thanks for the input.
Are Okna prices competitive? Is there an average rate for installation? Like, can I factor like $200 per window for installation purposes?
Also, is 0.1 of a difference in U factor major?
I appreciate your help.

Tough to say what your contractor will charge for installation because there are several different levels.

I would look at the Okna Insul-Tec (500) new construction. You can order it with extension jambs and it is about as cut and dry as it comes.

Where in PA are you located?

as you stated, the Interstate double hung in double pane has a ufactor of .29 whereas the okna has a .25 . thats a .4 difference. additionally, the okna is made under tighter manufacturing tolerances and is an overall more solidly constructed window.

Im in Northeastern PA, near Scranton. I told my builder to look into Okna and will get a quote myself.
The builder I am leaning towards, that quoted me for Andersen 400 Woodwright, got a quote from Pella for vinyl and he said that it was $10,000 less than the WoodWright.
I havent looked into the Pella vinyl and Im pretty sure thats what we have in our townhouse right now. Are those comparable to Okna?

I appreciate all your help!!

In a word, NO and in my opinion Pella vinyl may be worse than Interstate. There is a very good reason they are $10g's less because there is a ton less quality. Andersen 400's in my opinion are still the best window Andersen makes in spite of their trying to reinvent themselves as a custom window company.

No !!!! pella vinyl windows are bottom of the barrel as is andersen vinyl ( silverline).
some other higher end vinyl brands are soft lite, sunrise, and gorell.
its amazing how so many local contractors dont have a clue when it comes to quality.

+1

Feel free to post up a take off list and I am sure someone can get you some pricing.

How many openings do you have?