It seeps out over time (20-30 years depending on product) It does make a difference thermally. I opted for.

I would look into some of the newer glass coating such as LowE-4. They are pretty amazing at blocking the solar heat of the sun in the summer.

my options are low-e3 clear with argon or low-e/clear..which would u say is best to go with? thx!

Replacement windows have caused confusion to Homeowners for many years and there is always one question what window should I get?

When dealing with window salesman, each one will have a Cadillac of all the windows with all kinds of fancy names for bells and whistles.

If you want to get a good window and cut through all the BS, look at the windows
U Factor. UFactor measures the amount
of heat transfer and that tells you how well this window insulates. Remember, the lower the number, the better the window.

No matter where you getting your window from or who will sell you the window, ask them for NFRC sticker to verify the windows
U-factor. If you look this up, NFRC
stands for the National Fenestration Rating Council. That is very important. So if you have one window with a U-factor of .23 and the
other is .36, you want the window with a .23 U Factor.

Also very important to keep in mind that some use deceptive practices, some windows will show a low U-factors, so don't fall for that, read the small print at the bottom... some will says that the U-factor is being measured from the center of the
glass which will not do you any good. You need the full unit Ufactor because that the only one that matters, so make sure that the UFactor is for the whole unit and not just the glass.

As Argon gas goes, most definitely and today most manufacturers don't charge for that extra and have that feature in every window. Also some offer triple pane windows with Kryton gas, they cost a bit more and they can really get a
window down under .20 Ufactor, but if you ask me its a waste of extra money spent, not only this windows heavy, they will cause faster wear and tear on everything, but some manufacturers offer some real nice warranty with it.

Now about Low E Glass, this is a layer of
silver oxide particles in the glass which reflect radiant heat back where it came from... so in the summer it will reflect back to the outside, in the winter back to the inside.

With that said, you have to watch windows with Low E Glass. It's been known for this windows to melt siding on the adjoining walls of the house, or cause damage to houses located in close vicinity. I have seen it on a few occasions, and I didn't know what it was or how it happened, but after doing a little research for a customer, sure enough, the reflection from theirs new windows caused siding melt down on the adjoining wall and every one was "dumb founded" at the time trying to figure out what could have caused that.

That is about it, I hope you find this helpful and if you like to see a video about this, take a look at this video it offers some explanation

Good luck

thanks for the detailed info! much appreciated!