Viewpoint is Norandex's private label window made by Atrium. I a not familiar with Moss.

U4 is probably a made up name for triple coated LoE, based on the SHGC you posted. I don't recall whether Atium uses Cardinal or PPG but they would be the equivilent of 366/SB70XL respectively.

I think you are confused about U4 coatings vs argon filled. What you want is LoE glass with argon gas.

Viewpoint is a lower end window made for house flippers or poor newlyweds.

I would look for some other brands. Norandex carries Simonton Prism Platinum and Softlite Classic, so you should be able to get either of them and they are both better windows than Viewpoint.

+1

Windows can make or break the home in terms of performance and unless the home is sticked out, you have time.

Get a better window and some of the brands that Eco mentioned are really solid performers.

Thanks for the info. We have looked into a few other window brands but they are WAY out of budget for our home. We have to install 44 windows - and Yes - the house is already sticked out, and wrapped and waiting on windows. Here is the link to the U4 info, and yes I believe it is just another Low E coating on the inside pane of glass.
http://www.mosssupply.com/U4CoOpBrochure.pdf

BTW two of the three of the local window salesmen we're dealing with are saying that argon is not recommended in our area, and will leak out anyway within a few years. I was just hoping someone had experience with the u4 coating.

Here is a link that might be useful: U4 brochure for Moss windows

Two of the three salesmen should stop selling windows that leak then.

A well prepped glass spacer will not leak the argon out and certainly not a rate that makes it foolish to get in the first place.

The air leakage rate is higher than recommended and the thermal number (U-Factor of 0.29) with an interior low-e is not very good either. Most window with the interior Low-e are getting U-Factors of 0.24 and below (the one I can think of off the top of my head is a U-Factor of 0.22 which is +30% better than the unit they have listed).

Why did you builder leave it to this stage to make a material decision?

I would be very leery of using any supplier who told me he had issues with all of the name brand window manufacturers he is naming. Sounds to me like the issue is in his company or office and he is passing the buck.

It's not that Atrium is that bad of a brand, it's just that there are better windows available in the same general price range. Anyone who tells you Atrium is a better window than a Simonton Prism Platinum/Reflections 5500 is not telling you the truth. It's likely they make more profit on the Atrium and that's the reason for the deception.

In NC, I would be looking at a combination of dual coated and triple coated LoE. I would not buy any window from a salesman who claims their windows will leak out all the argon gas. It is a further indication they are selling junk.

If you can get Simonton, get that window before the Atrium.

+1 to both Eco on Millworkman's comments.

You need to get some prices on the windows to compare.
My local Norandex dealer does not like Soft-Lite and will not mention them unless asked. They like to push the ViewPoint, Simonton and Walsh. They don't even display the Soft-Lite. That being said the the Soft-Lite Classic has a good price for what it is and is good at what it does.The Simonton's are a little overpriced and the Atrium's are priced for what they are.