Cost of Low-E Glass (ie: per square foot)

stevekatFebruary 27, 2009

I am getting quotes for glass walls for my home. I have five openings, ie: 12 x 7.5, 12 x 7.5, 12 x 7.5, 13 x 7.5 and 6 x 7.5. The plan is to used extruded aluminum u-channel typical for commercial store fronts and install either laminated 1/4 (2 x 1/4 panes,) or IGU's with 1/4 panes on each side. At least one pane would likely be tempered. The 1/4 glass is being used for strength/safety as the glass wall is elevated.

The low-e glass being considered is PPG Solarban 60 with Atlantica Tint. This is low solar emissivity soft coat. The tint and low-e panes can be separated, but PPG offers a product with the tint and low-e coating on the same pane, and this seems better for the IGU, if we go that route.

The glass company say the IGU and laminated lites shall not be much different in price. While I haven't received all quotes yet, I am being tenderized that I should expect the cost of the glass only (either laminated or IGU unit) to come in around $30 to $35 a square foot, before installation or frames. The project is in SoCal.

This cost for glass only is astonishing to me - close to $300 a square meter. Is this typical for this type of product? Anyone have any cost reference point for this or a similar product. Also curious if anyone was aware of the likely cost to the dealer from the distributor for the glass unit, so I can evaluate a fair margin when negotiating. I had thought the per square foot cost might come in around $20 - the higher potential $30 - $35 price is a surprise. I have had generic low e suggested by one glazers supplier, at around $15 psf, but it appears to be hard coat and high solar emisivity, not really meeting our requirements.

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I am not sure from your original post, but are you saying that you are looking at IG's with two 1/4" tempered lites or IG's with 1/4" laminated as both lites of the IG? Why laminated? is there a particular reason?

Solarban 60 is a dual-silver softcoat. Dual-silver is considered to be a moderate solar gain coating. Adding the tint will lower the SHGC but unless you are looking specifically to block solar glare, then I would recommend that you look into triple-silver coatings such as PPG's Solarban 70XL or Cardinal's LoE3-366. Either of those coatings will block a significant portion of solar gain thru your windows, possibly eliminating the need for the tint, unless you you have a specific reason for wanting the tint.

You mention that the laminated glass and IG have roughly the same cost, but are you comparing monolithic laminated with a dual pane IG?.

    Bookmark   February 27, 2009 at 8:16PM
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Actually, I am considering one of two options:

1) Solarban 60 w/Atlantica tint in a 1/4" - 1/4" laminate (clear on the other side of the laminate. Not an IGU.


2) Solarban 60 w/Atlantica tint for a 1/4" outside pane of an IGU, with a clear 1/4" inside pane of an IGU.

In 1 and 2 above, one piece of glass of each would be tempered if possible.

My home is in SoCal and not very well insulated. It was built in 1969. The sun set across the back of my home over a ridge, shining directly into the house, through walls of windows, heating it up to such a degree that the air conditioning cannot even come close to keeping up with the heat. Also, glare is a big problem at the end of the day, hence the Atlantica tint. So the goal is to reduce the solar heat gain, and knock down some glare. I was less concerned with the insulation quality, because the house is poorly insulated. Though I would indeed prefer a good U factor. However, I was thinking about using only laminated (not IGU) because IGU's have a limited lifespan - didn't want to have to replace them down the road when the seals blow - so thought giving up the U factor benefit of an IGU for longer lasting laminated lites might make sense.

I am proposing using two 1/4" panes in the laminate option, and 1/4" for inside and outside in the IGU option for strength (with at least one pane of each unit being tempered.) The reason for wanting the extra strength is that the house is on a hillside and the windows are very high off the ground - they are floor to ceiling. Want the strength over concern about some accident resulting in someone going through lite.

I also thought that since I wanted to knock down the glare, and since the Atlantica tint would also further reduce solar gain, in addition to the soft coat of the Solarban 60, that the SolarBan 60 might be adequate. Also no one I've talked to even mentions the 70XL even though I am aware of it. I am surprised about how few Low-E options are presented by window/glass companies. Either they don't know about them, don't understand them, or believe their customers are incapable of understanding the differencea. I am interested however, in minimum solar heat gain.

I think the visible transmission using SolarBan 60 Atlantica is about 54% (with the laminated and IGU solutions being slightly different.) And that the SHGC comes in about 0.27 (combined Solarban 60 and Atlantica.) Regular SolarBan 60 without Atlantica tint comes in around 0.38 SHGC. I like the idea PPG makes SolarBan 60 with the Atlantica tint (in one piece of glass.)

If there was a way to cut down the glare, without having the outside being reflective, I'd consider losing the tint and having a clearer glass like the Cardinal 366 or the SolarBan 70XL, but the tint is to deal with the sun glare. I guess I could order the SolarBan 70XL in Atlantica tint to get even better SHGC, if PPG makes the 70XL in tint (on one piece of glass.)

I also was interested in the self-cleaning coating, but upon hearing of the potential cost even without it, was a bit scared off. So I am trying to get a sense of what to expect for the per square foot cost, so I can both negotiate from a position of knowledge, and also get a sense of what I should be able to afford, ie: adding self-cleaning, etc. for the scope of my job. I am going to need about 400 square feet over the sizes indicated in the prior post.

    Bookmark   February 28, 2009 at 2:52AM
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You have definitely done your homework, hopefully I can offer a few suggestions...

As I think that you already know, using coated laminated glass will give you the same SHGC performance as you would get from an IG, but at the loss of the IG U-factor improvement.

Keep in mind that laminated glass will generally have a shorter warranty period than will an IG (depending on manufacturer - but shorter warranty for lami versus IG is fairly consistent in the industry).

Depending on the IG manufacturer (and materials), IG seal failure is not likely to be a problem. The better systems in use today have seal failures significantly less than 1%. There is significantly less reason to anticipate "down the road when the seals blow" than you might think.

There is at least one other consideration when dealing with internal softcoat coated laminated glass.

There are several different laminated glass interlayers in use today. It is likely that you will be looking at a PVB interlayer since a significant majority of laminated glass windows use PVB interlayers.

Without going into all the technical details, not all laminated glass manufacturers who deal with coatings are comfortable with the compatibility or longevity of laminating softcoat coatings with PVB interlayers. Cardinal, for example, doesn't even offer an internally coated PVB laminate.

Okay, all that said, I am really not trying to talk you out of using a coated laminate, I am offering a few other considerations...hopefully not making your call more difficult.

In the case of an IG I would agree completely that getting a coated LowE coating or getting the LowE coating on a tinted lite is superior to an IG with separate coated lite and tinted lite.

"I guess I could order the SolarBan 70XL in Atlantica tint to get even better SHGC, if PPG makes the 70XL in tint (on one piece of glass.)" I believe that PPG does offer the 70XL tinted as well, if so I think that it would be worth your while to check it out.

"Also no one I've talked to even mentions the 70XL even though I am aware of it. I am surprised about how few Low-E options are presented by window/glass companies. Either they don't know about them, don't understand them, or believe their customers are incapable of understanding the differencea." --- All of the above?

I am curious why you want to temper the glass in the laminate? While I understand (and agree with) your desire to temper the lites in the IG (I would do both lites at your sizes - I would also consider thinner glass since tempering would allow you to safely go thinner), but since laminated glass is a safety product that meets all the same safety codes as tempered (actually exceeds tempered in some respects), from a strictly safety standpoint there is no reason to temper the glass as well as laminate it.

Although some folks advertise "self-clean" glass, other folks call it "easy-clean" glass just to avoid the controversy of the glass "cleaning" itself. It is a photo-catalytic titanium dioxide coating that does work really well. A few window companies offer it as a standard, others as an option, and others don't offer it at all.

And while I don't deal directly with glass or window pricing, based on what you are asking for, and since you are in SoCal, I don't see that your glass quote is really out of line, which doesn't make it less painful. You are considering some potentially expensive options.

    Bookmark   March 1, 2009 at 10:24AM
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Oberon, thanks for the insights.

I just did some research and it appears a Solarban 70XL with Atlantica tint single pane is available.

I didn't realize that laminated had a shorter warranty than IGU's - but I'd imagine either warranty is far less than the expected lifespan of each unit. If I went with laminated, I think I'd try to use an SGP interlayer - I read some info at the Cardinal site, as you referenced, that PVB could lead to some de-lamination around the edge or some corrosion of the softcoat on laminated units they tested. They suggested Dupont SGP if one had to go with laminated lites.

I'd prefer an IGU if I had confidence they would last - perhaps I am being overy pessimistic. In referring to a 1% failure rate - any idea what time period that might refer? If I could expect that failure rate at 20 years or beyond, I'd feel very comfortable - I don't mind replacing one or two of these very large lites over a very long time span, but replacing all or most of them is something I'd like to avoid.

I've also read about spacers - claims that foam non-metal spacers for IGU's can be more reliable and longlasting - one company is EdgeTech with a product called SuperSpacers. Any idea if this type of system is preferable and adds to longevity? I guess the other issue is if IGU's are repairable. If a unit fails and someone can come in and drill a hole and evacuate the unit of moisture, or mitigate other typical problems, affordably, that would help in the decision.

The reason I was considering tempering on at least one side of the laminated lite was strength - the lamination provides safety - one is unlikely to go through it. But does the lamination make it less likely to break (crack) upon a modest impact? In addition to the safety issue of not going through it, I'd like it to resist breakage. On other hand, in thinking about it, if the project were significantly less expensive by using 1/8 inch, and I had a cracked lite at some point, replacing it would be far less than upgrading the entire project to 1/4 inch.

Also, in considering IGU's, it sounds like going 1/4 and 1/4 maybe be a bit extreme. In a case where the units are maybe 25' above the ground in a glass wall configuration, is and IGU with tempered 1/8 inside and 1/8 outside, something typical from a safety standpoint. If so, this option could be attractive.

So my thinking is potentially changing...if IGU's are available with more longevity than I thought, and I can use glass of more modest dimension (thickness) I can gain the U-Factor I'd prefer, and probably significant cost savings because of the lesser cost of the thinner (tempered) glass.

If you have any experience with the self-cleaning/easy clean glass, I would be interested in hearing an opinion or observation. Most of the windows shall be very difficult to access from outside because they are high off the ground, so having the longest period between manual cleaning is something I am highly in favor of trying to accomplish.

Also, any idea of what glass company margin to the consumer is on these products, from the distributor?

    Bookmark   March 1, 2009 at 3:57PM
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Does anyone know if a laminate with Low-E coating (apparently in the PVB laminate layer) used in hot climates will perform as well or close to that of a Low-E IGU unit?

    Bookmark   April 22, 2009 at 7:00AM
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SHGC will be pretty much identical, but U-factor of the laminated window will be the same as a monolithic single pane of glass at the same thickness - which will be a good bit less than the coated IGU.

    Bookmark   April 24, 2009 at 10:28PM
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