I feel like a ditz but can someone give me an idea of how to identify whether a window has low e glass or not. Also, is there different qualities of low e glass? I’m struggling with the decision on whether or not to replace some windows before I re-side my house.
thanks,
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Replies
Take a lit match or candle and hold it up to the glass. 4 images of the flame will appear. If Low e, one of the images will be slightly different in color. The location of the different one will be the side of the pane that the coating is on.
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Cangowrongwillgowrong
Wait a minute where are you? the reason I ask is replacing double pane windows for some with low E isn't a perminent solution.. Most Argon will have leaked out within 10 years according to all the stuff I've read.. the argon is what makes a window efficent.. Not just the Low E
The cost of replacing windows is high enough that a long payback can be expected in all but the coldest/ warmest states..
A better test (again using a candle) is on a very windy day does the flame flicker indicating wind leakage. IF it does and you confirm that it's the window itself and not the installation of the window at fault then replacement windows are called for..
if it's the install (air leaking in around the window) then caulking is called for..
Low E glass is not dependent on argon (or some other fill gas) to be effective. Check out this link:
http://www.efficientwindows.org/lowe.cfmFrom what I've read, the technology has increased significantly so gas evacuation is not nearly as much of an issue with new windows as it was 10-20 years ago.You are correct that air infiltration is the first thing to examine. You can lose a lot of BTU's with a leaky thermal envelope.
Jon Blakemore RappahannockINC.com Fredericksburg, VA
Jon,
the Low E works but it's the Argon gas that provides the best thermal protection once the sun goes down..
Remove the argon gas and the windows aren't as thermally efficent..
I've watched Marvin windows, Andersen Windows, and Weathershield windows being made and none of them have what I would call really great air sealing capability. It's sort of like an old tire. Sooner or later the air will leak out and then the tire goes flat.
Argon filled is snake oil. It is sold as slowing a convection current from forming as cold air on one pane falls and warm on the other rises to potentially stopping a tornado from forming inside you IG unit. Bawahahahhahaha....
It adds a fraction to the U-value and will eventually leak out anyway, if it was ever really there.
Argon is a byproduct of manufacturing O2 and nitrogen and someone figured out a market for it... Kinda like the guys in Asia that sell birds so you can let them go and bring you good luck... so they can catch them again and.... well you see where this goes... the guy with the good luck is the one catching and selling.
sledgehammer
Well the three manufacturers I watched use Argon. True it will leak out eventually but it does help.. I'd rather have it than not have it.
There are different types of LowE coatings and there are (arguably) slightly different quality levels within the various types. Quality of the coating is much less of a concern though than is the quality of the IG unit.
LowE coatings improve window performance in two ways. First they block radiant heat and second they improve the overall U-value (conductive heat loss) of the glass system as well. Depending on what you really want from your windows - for example solar heat blocking versus solar gain - can make a difference in which coating might be best for your specific application.
In ALL circumstances, a window with a LowE coating will improve energy performance over a window without a coating. The cost of a LowE upgrade (if it is an upgrade - I would suggest that most upper end windows include LowE as a standard anyway), will payback fairly quickly - particularly if you are in a more harsh environment. Field studies in cooling dominated climates, for example, have clearly demonstrated actual savings as high as 35% (possibly as high as 50% in some instances) in total year-round home energy usage when using a low solar gain LowE on the windows. Real numbers.
Argon gas between the lites of an IGU results in an increase in unit performance of 16% at 100% fill rate. Drop the fill rate to 75% argon and 25% something else (typically nitrogen) and the unit energy performance is 12% better than when using an straight air fill. At 50% argon fill the performance is 8% better (notice the pattern?). Energy performance improvement is linear from the 16% at 100% down to whatever fill level the manufacturer desires.
The system used by all Andersen, all Marvin, and some (but not all) Weathershield windows (and I mention these companies because they were mentioned in a previous post in this thread) incorporates a dual-seal stainless steel spacer in the IG unit. Dual-seal means that the spacer is attached to the glass with two different materials - polyisobutylene or PIB as the primary or air/moisture seal, and a specially formulated silicone as the secondary or structural seal. PIB is the only butyl known that is impermeable to gas - including argon.
Back in the dim and distant past of IG history, IG's were manufactured using various materials to affect a seal between the glass and the (generally) aluminum spacer. Among those materials were polysulfides, hot-melt butyl's, assorted organics, and even silicones.
What was consistent about those IG systems was that none of them were (or are since some companies still use them) impermeable to gas passing directly thru the materials when used as a single-seal system - meaning that there were no separate air/moisture and structural elements.
Some of those materials did quite well at blocking gas migration, but provided no structural support. Others provided structure, but allowed gas (including air and moisture) to pass through the seal. This was not technically a seal failure, it was simply that the seals were not “gas-tight”- the nature of the material - much like filling a latex balloon with helium - the gas eventually simply dissipates thru the material. Dual systems were developed to help prevent that problem.
The dual-seal system currently used by the companies mentioned has been tested and measured at about 1% argon loss per year. This level has become something of an industry standard although not officially anywhere that I am aware of.
Oberon,
Thank you for that tutorial, My experiance with the three companies was a few years ago so I wasn't aware of progress on the sealing issue. The loss rate of 1% a year means that if I have the improved seal I can anticipate a usefull reduction in thermal loss for the rest of my life.
Can you tell me when the improved seals were put in use?
Frenchy,
There is something of a parallel between the development of warm-edge spacers and dual seal systems.
The first wide-use warm edge spacer system was probably PPG's Intercept which was introduced in about 1992 (give or take a little). Cardinal followed with their XL stainless steel system maybe a year or two later.
Intercept was introduced as either a single or dual seal system while XL was introduced (and is only available today) as a dual seal system.
Intercept is available as either a stainless steel or as a tin-coated steel while XL is only available in stainless steel.
XL uses PIB/silicone for the two parts of the seal while PPG recommends PIB and either a polysulfide or a polyurethane as the secondary system. PPG will say that using a silicone is acceptable, but they prefer the other two options. PPG also suggests the use of DSE - which amazingly enough stands for Dual Seal Equivalent - rather than a dual seal for several possible reasons and while some people will suggest that a DSE will perform as well or even better than a dual seal system, others will disagree.
IG units made with the Cardinal XL spacer are produced by Cardinal in their own IG facilities while the Intercept spacer is produced by PPG but then sold to window companies who make their own IG units on site.
So why the emphasis on those two? Well, all three of the window companies that you mentioned used the Intercept system when it was introduced. Two of them converted to the Cardinal system after some years of using Intercept. The other company uses several different spacer systems including (I believe, but I could be wrong) both XL and Intercept (and Swiggle too as I recall...).
The change from one spacer system to another wasn't something that occured all at once. In both companies there was a transition period between systems that lasted several years in some cases. I would suggest that for about the past six to eight years or so both companies have used Cardinal's XL exclusively - but don't quote me because as I recall memory is the third or fourth thing to go. Luckily, I can't recall what the first two were...
Was the move away from PPG precipitated by any issues in the field or were there other factors in play?
Jon Blakemore RappahannockINC.com Fredericksburg, VA
Jon,
I am not in a position to really know why any company changed from one system to another.
Certainly people can and do speculate about such changes, and no doubt performance, economics, and even performance economics, would all play a part in any decision like that, but for specifics only the folks on the "boards" of the different companies really know the final answer.
Edited 9/5/2008 6:59 am ET by Oberon
How does one determine the % argon in an IG. I repair collapsed cardinal glass. I frequently see houses with some units touching and others spaced like the day they were made and no sign of failure. Is it safe to assume those units that didn't collapse and had a spacer system that is know to leak argon .... never had argon to begin with?
Sledgehammer, <!----><!----><!---->
In the factory there are a few different ways to measure argon fill in an IG. A couple are destructive and one is not destructive. In the field there is only one way to accurately measure argon in an IG - not counting collapsed glass since the collapse indicates that the argon has gone elsewhere - but not how much is actually remaining...<!----><!---->
In the field, the only way to measure argon is using a Sparklite or "sparky". Sparky causes a high voltage spark to ignite inside the IGU which causes the argon atoms to emit light in a spectrometer. Sparky does not affect the IGU seal which is considered to be a good thing!<!----><!---->
Prior to the advent of the XL system, Cardinal used a single seal polysulfide aluminum spacer in their IG units. What no one fully realized at the time was that the polysulfide would pass gas (in a manner of speaking). Both argon and "normal" air would permeate the polysulfide. And I don’t think that at the time anyone fully appreciated that argon would pass through the polysulfide about three times faster than would air (principally nitrogen). And, since there would be a much higher concentration of argon inside the IG than in the air outside, the argon inside the IG had a very pressing need to go outside the IG, so it did. Unfortunately, since air didn’t enter the IG space as quickly as the argon could exit the space the result was collapsed glass. And I think that you already knew all that as I recall from a thread a few months back…<!----><!---->
It is entirely possible that the units that don’t have collapsed glass never had argon in the airspace to begin with. That would probably be what I would suggest if asked in the circumstance that you describe. Since argon fill wasn’t really all that common not too many years ago, so I would not have any problem with that explanation.<!----><!---->
Another possibility is that the unit could have had a seal failure at some point that allowed outside air into the IG somewhere in the past. In the right environmental conditions, it is entirely possible to have a seal failure in an IG that doesn’t result in the “typical” moisture problem in the airspace. <!----><!---->
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Andersen realized and resolved the collapsed glass issues in the early 90's. However, I notice in other manufacturer's windows made today a 'collapsed glass' look, where the glass looks concave, mostly in the vinyl new construction windows. Actually, our neighbor's new house has United windows where the glass is decidedly concave. To the point where I believe the GBG grilles are stopping the glass from collapsing further. I've seen M & W windows collapse and spontaneously break in windows less then 8 years old. One house of M & W windows had probably 500 panes of TDL glass that was breaking all over the place. I measured the glass in the small panes and they were touching in the middle.Have some manufacturers never adopted the improved method of manufacturing IG glass?.View Image
As I mentioned earlier, the memory is about the third thing to go (and I was typing and watching the ballgame at the same time...).
Anyway, I may have gotten a bit ahead of myself when comparing Intercept and XL and who used which spacer when last night; and this morning I am trying to remember if it was actually the Intercept that Andersen used prior to the XL - or if it was different system. I am confident that Marvin did use Intercept, but I am waffling on AW at the moment. I am now going to have to check when I get to work this morning....
follow up - both companies did use Intercept for at least some products.
Edited 9/5/2008 6:57 am ET by Oberon