Well said. Usually, in bows, glass is plentiful but I would always prefer to have more of it wherever possible. The energy numbers are not quite comparable though. The Okna will have the better thermal and air tightness number to go with the cleaner frame sizes.

Agree with washington. The Okna will have much better performance numbers than the simonton; that includes uFactor and air infiltration. The okna is also designed better and much nicer looking.

Air tight numbers (air infiltration rates) will depend on flanker styles. Casement flankers such as the Okna 700 series make both a wash. There is still some question with regards to testing for air infiltration rates that can make that number very deceiving as well. Whichever you choose make sure that the unit is properly supported and the head and seat boards are insulated. If its maximum glass space you wish to achieve perhaps looking at the Marvin fiberglass line would be a better option?

Again, marvin fiberglass have very high air infiltration numbers and the Ufactor is rather high which means less efficient. The marvin infinity is nice looking, better looking than the integrity which i think is cheap looking.

@branlance I think it needs to be clarified that if casement flankers are the choice then air numbers are not in play. What is the air infiltration numbers on the casement series? Everyone keeps bringing up air numbers when that is irrelevant if casements are the choice. Go with casements on either brand and air numbers are not in play. U ratings are completely different but a quality bay or a bow do not take up enough square footage to substantially effect your energy bills. Let's not also forget that air numbers are based off of a 35 mph wind load. Can anybody enlighten the group as to how many days in a year we had substained 35 mph winds. It's completly overblown when look Iooking at total energy usage.

Does anyone giving there opinions and views about this topic have direct relationships with any of the manufacturers being discussed? I surly wouldn't ask a Ford dealer if Chevrolet was equal. Lol. I'm pretty sure his opinion would lean to be a little biased towards his product.

jayandrita, while I agree with you that AI ratings are generally closer (all pretty good) among casements as opposed to double hungs and other config's, air infiltration testing is at a 25mph wind load, not 35. Furthermore, while 25 (or 35 ;) mph) winds are not the norm, these ratings most certainly speak to the manufacturing tolerances and overall structural integrity of a given product, which in turn beget a product that will perform better for longer, therefore offering an measurably better ROI. A small gain per year adds up rather quickly over the service life of a 30+ year investment. On square footage of the wall area, this is one of the largest openings in the exterior walls of your home. To discount this in calculating efficiency would be a grave mistake.

In summation, the Okna is the clear performance champ here, both thermally and structurally ( u values are tested at a 5 mph wind load). That said, I'll reiterate my own previous advice that both the Okna and Simonton will perform in a range from superb, to pretty darn well.

On Marvin FG options, I would rank them as follows:

1) Integrity Wood/Ultrex: Lacks somewhat in performance, but it is an attractive product with a real wood interior at a fair price. Performance is still respectable if not good in comparison to other wood windows.

2) Infinity Ultrex : Similarly lacking performance with a fake wood veneer interior and a price tag that is generally astronomical. In white (int), it is admittedly better looking than the all-ultrex Integrity

3)All Ultrex Integrity: Looks like a mechanically fastened vinyl window from 30 years ago and lacks in performance to boot. This product has to fit one's very narrow set of appearance requirements (painted off-color interior) to be worthy of any consideration. If not, it has ZERO appeal for me.

For the record, I sell and install products from all three manufacturers (Simonton, Okna, and Marvin) among others, so take that for what its worth... Not sure if it would be more appropriate to say that I have no horse in this race or ALL horses, lol.... Can't speak for the other contributors.

@HomeSealed Exteriors Good points and I really like Okna. My main point is that with casement flankers air is not a topic. The consumer seemed to be open to casements as an option since she mentioned the Okna 700 series so casements take away that concern.