Durability of surface 4 low-e coatings?

OaktownJuly 3, 2013

Hi, I'm very impressed by the knowledge here and hoping someone can help me out.

We are considering a window option that would have two low-e coatings and I have not been able to find information on the durability of the coating on surface 4. Specifically it is the Cardinal LoE-180/LoE-i89.

Condensation is not much of an issue in our climate (California) but what I'm worried about is how this kind of coating would stand up to cleaning and, for example -- young kids taping things on the windows.

Any input would be really appreciated.

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I don't see them too much around here as the condensation IS an issue being in WI, however as Energy Star guidelines for u-value tighten next year I'm sure that we'll all be getting a little bit more familiar with them. Durability has not been an issue in my understanding. If Oberon happens to see this thread I'm sure that he'll be able to add some additional insight .

    Bookmark   July 3, 2013 at 6:04PM
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Thanks HomeSealed! I do hope Oberon will see this, I found an old thread where Oberon wrote that:

"However, both i81 and LoE-180 are sputter coats, neither is a pyrolytic. While LoE-180 can only be used inside of an IG, i81 can be used on an exposed surface because it doesn't use silver as part of the interlayer (no corrosion issues) and because it is physically much more durable than a standard LoE softcoat."

Since the i89 is the replacement for the i81 I would love to hear more!

    Bookmark   July 3, 2013 at 6:29PM
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Yes, it can pose a durability issue. Surface 4 would be on the outside of the glass and it would be a " hard coat" lowE; you CANNOT put soft coat on the outer pane.
What happens to hard coat on surface 4? You can get glares, scratches, dust, dirt, and as HomeSealed alluded to,alot of condensation. This is the reason why many companies refuse to embrace hardcoat on surface 4.

    Bookmark   July 3, 2013 at 8:15PM
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Actually mmarse surface 4 is the very inside surface, 1 is the outer most surface. And double Low E coatings are generally done surfaces 2 & 4 per Pilkington but I cannot link the pdf here.

    Bookmark   July 3, 2013 at 8:46PM
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Sorry if I was not clear, all of this terminology is new to me! Yes, I meant that the coating in question is on the room side of the window.

I hear that LoE-i89 is a soft coat (MSVD and not pyrolytic) but somehow it is supposed to be more durable than most other soft coats, I just don't have an understanding of what "more durable" means. Cardinal's website says you can clean with Windex but not abrasive cleaners or a razor --not much of a surprise. What I'd like to know is, if, just for example, my kids tape a picture to the window, and I use my fingernail to get the tape off, will that damage the coating? If I paint the interior and accidentally get some paint on the glass, when I take it off will the coating be ruined?

Our contractor is going to try to get more information from Cardinal, which I am happy to pass along if it sheds more light, but I would love to get opinions or hear from folks who are more impartial :-)


    Bookmark   July 3, 2013 at 11:04PM
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Putting a low e coating on the exposed inside is overkill and foolish, especially if it is soft coat. It will not last, or help your condensation in a short period of time.

    Bookmark   July 4, 2013 at 10:29PM
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****never mind****

    Bookmark   July 5, 2013 at 8:04AM
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Windows on Washington Ltd

Ha ha!!!

Herb is on board with the Grumpster.


The above statement about surface 4 coat Low-e is incorrect.

Nobody specifies soft-coat (like that on the interior of the IGU) on surface 4.

I have not seen any observable data that shows that these coatings will break down over time or get damaged by normal usage. I am pretty certain that Cardinal and Guardian would have vetted these coatings prior to offering them to the consumer.

The surface 4 coatings will have a slightly lower CR number but this is to be expected as a result of the lower surface temperature.

    Bookmark   July 7, 2013 at 8:52AM
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Sorry folks are grumpy!

Just wanted to let you all know that I appreciated the input/clarification. In the end, cost is driving our decision, as the price difference in our window quotes for including the i89 was considerable (almost as much as triple pane).

    Bookmark   July 19, 2013 at 12:05AM
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Windows on Washington Ltd


That Grumpy cat post that Millworkman put up was not for you or any of your posts.

It was for Jumppilotdm.

Thanks for the update and be sure to post up some before and after pictures.

    Bookmark   July 19, 2013 at 1:13AM
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Does ANYBODY do a surface 4 soft coat? That sounds ridiculous to me... Every one that I've ever seen is a hard coat and their durability s just fine. There are pros and cons of course( condensation) , but durability is not an issue that I've seen.

    Bookmark   July 19, 2013 at 8:08AM
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From what I understand and I am no glass expert but they now have a sort of "sputtered hard coat" Low E adding Iridium to give it durability (Cardinal LoE-i89 for one). It also does not contain the blueish tine that typical pyrolitic or hardcoat Low E has.

    Bookmark   July 19, 2013 at 9:50AM
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Windows on Washington Ltd

Paging Oberon.....

    Bookmark   July 19, 2013 at 11:03AM
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Good morning,

When people think of LowE sputter coatings they typically think silver since the vast majority of sputter coatings available use silver as the operative layer in the coating stack.

But because silver tarnishes when exposed to oxygen, LowE coatings made with silver need to be protected from oxygen exposure.

This is accomplished first, by sandwiching the silver layer between protective layers when the coating is being manufactured. But since the protective layers can be damaged in normal usage, potentially exposing the silver, sputter coats are further protected by encapsulation inside the IG airspace.

Two changes would be needed in order to produce an exposed sputter coat. First, use a metal that doesn't corrode when exposed to the natural environment, and second devise a protective layer that can withstand normal wear and tear.

Although silver is by far the most commonly used metal for sputter coatings, it isn't the only one. Gold is used in some very specialized applications. AGC uses titanium rather than silver in their Ti series of sputter coats. Tin can be used, and even stainless steel has been used in some applications. Pyrolytic coatings use fluorinated tin oxide as the base coating, often with other metals or oxides added for specific applications.

In I81 and now I89, Indium tin oxide replaces silver as the operative layer (avoiding corrosion), and the stack is protected by using a tough outer layer that resists scratching and abrasions - which does not mean you should take steel wool to the coating to clean it.

Millworkman hit the nail squarely on the head, I89 is a "sputtered hard coat" and as such it should be able to withstand the same sort of day-to-day activities of any of the pyrolytics. You can damage it, but you can damage uncoated glass as well if you abuse it.

I can't imagine that sticking and removing tape should harm the coating in any way. In fact, the protective layer has an added benefit of making the glass "smoother" and possibly even a bit easier to clean (not a manufacturer claim - just my opinion).

    Bookmark   July 20, 2013 at 10:09AM
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Awesome explanation, thank you! Now I know what I'll be missing;-) Hopefully the price will have gone down if I ever have to buy windows again.

    Bookmark   July 21, 2013 at 12:26AM
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Windows on Washington Ltd

As always...great information Oberon.

Sputtered "hard" coat it is.

    Bookmark   July 21, 2013 at 11:17AM
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You are welcome Oaktown and thanks WoW.

One other little piece of trivia concerning surface 4 coatings.

I81 and I89 are a good bit thicker than a "regular" sputter coat, but much thinner than a pyrolytic.

By comparison, if I89 was the width of a nickel, a basic pyrolytic would be about six feet thick.

    Bookmark   July 21, 2013 at 8:56PM
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Oberon is quite correct correct above. The ITO coating is, I suspect, no more susceptable to scratches than the glass itself (it is harder than glass). Unlike, pyrolytic hardcoats, it is also very smooth and as a result isn't susceptable to metal marking and haze and cleanability issues.

All side 4 low-coatings (necessarily) reduce the glass temperature by a few degrees and as a result are a bit more susceptable to condensation. Whether this is a practical issue, remains a bit of an open question. I have some i81 units installed in my home in the upper midwest and have never had an issue with condensation (I keep my humidifier on a pretty moderate setting, however).

The only difference beween i89 and i81 that I'm aware of is a much lower reflectivity on the former,

    Bookmark   July 26, 2013 at 1:02PM
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