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 Post subject: Low E versus regular Low E
PostPosted: Thu Oct 28, 2004 1:05 pm 

Joined: Thu Oct 28, 2004 7:24 am
Posts: 5
Location: Reston, VA
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My windows have the regular Low E softcoat. The manufactuerer of my windows just stopped using the regular Low E and is now using the Low E 2.

I have 3 bedroom windows that face South so they get a lot heat in the summer.

Is the new Low E2 that much better than the old Low E? Is is worth upgrading the sashes to it or is it a waste of money?

The U value on my current windows are .33 R value: 3.85 Solar Heat Gain: .26

Thanks


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 Post subject:
PostPosted: Thu Oct 28, 2004 2:46 pm 

Joined: Wed Oct 27, 2004 11:25 pm
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SHGC is a scale from 0 to 1, the LOWER the BETTER. 1 is like no window at all - all solar heat is transmitted and 0 is like a brick wall - no solar heat is transmitted. Note that the SHGC rating is for the entire window. Therefore a window with SHGC of 0.20 will transmit half the solar heat as a window with SHGC of 0.40.

See http://www.efficientwindows.org/lowe.cfm for an explanation of different low-e coatings.


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 Post subject:
PostPosted: Thu Oct 28, 2004 2:55 pm 

Joined: Thu Oct 07, 2004 9:26 am
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Location: Atlanta
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I'm no expert, but I thought that low e was what they called the coating on one internal side of a double pane window, and that low e 2 was they called the coating on two internal sides of a triple pane window. I had never heard that there was a new type of coating out there. But I've been known to be wrong, so maybe I am in this case and I will learn something new today.


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 Post subject: Low E versus regular Low E
PostPosted: Thu Oct 28, 2004 3:15 pm 

Joined: Thu Oct 28, 2004 7:24 am
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Location: Reston, VA
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Hi Mark,
Regular Low E has the coating on the inside of the glass that faces outside. Low E2 has it on the second side of the glass that faces inside the house.


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 Post subject:
PostPosted: Thu Oct 28, 2004 4:24 pm 

Joined: Thu Oct 07, 2004 9:26 am
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Location: Atlanta
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You know I don't know jack about windows, but I do know how to search on the web. And when I found the below quotes (from two different websites and that seem to disagree with each other), I realized that I know less about windows.

Quote:
Q. Is there a difference between loe e windows and low e2 windows? If so, what are the advantages? Thanks for your reply.
Anonymous 9/19/04

A. There IS a difference between one low e and another. My understanding is that most of the actual glass manufacturers have different names for their regular and more advanced low e. For example, PPG calls their regular soft coat low e Sungate 100 and their more advanced is called Solarban 60. The Sungate 100 offers about 35% better overall U value (insulating value) than standard clear insulating glass. The Solarban 60(2) offers about 50% better overall U value that standard clear insulating glass. In addition, the Solar Heat Gain Coeffiency Rating and the Visible Light and UV energy Rating is better with the more advanced low e. There is also the area of the country to consider and the options of soft coat low e versus hard coat. It can be very confusing for the homeowner. Make sure that you know what you are comparing since many companies don't necessarily 'label' it correctly when giving an estimate. Low e seems to be the 'generic' name that all companies go by--referring to low emissivity. (I think low e2 is Cardinal glass's more advanced low e. But don't assume that the other low e isn't also the more advanced version without reading some literature or talking to the representative again.) Microsopically thin, virtually invisible, metal or metallic oxide layers are deposited on a lite of glass and sealed in an insulating glass unit. This reduces the u-factor of the window by suppressing radiant heat flow. Your more advanced low e usually equates to an additional layer being deposited on the glass. However, low e and/or the more advanced can also be put on 2 panes of glass instead of 1. This also aids in adding more insulating value. Whatever manufacturer you decide on, make sure that the low e you receive meets the energy efficiency of the Department of Energy's ENERGY STAR guidelines.
AND
Quote:
First of all, the superscript 2 in "low-e2" refers not to the surface the coating is on, but the fact that there are two vapor-deposition low-e coatings of silver separated by an antireflective layer. Second, your point about a low-e coating on the #2 surface not being useful in blocking outgoing heat loss is wrong. It works just as well as a low-e coating on the #3 surface. On the #2 surface (counting from the outside in), the low-e coating _reflects_long-wavelength radiation being emitted from the #3 surface (outer surface of inner pane of glass). The heat radiation is reflected back to the inner pane, which in turn heats up more and radiates its heat into the building.

If the low-e coating is on the #3 surface, heat from the room is absorbed by the inner pane of glass and heats up. Because of the coating, less of this heat is reradiated (emitted) outward, so most of it is reradiated back into the room. The net effect of the two low-e coating locations is almost the same. Both placements work nearly as well at blocking heat loss from the building.

I recommend low-e2 windows on north, east, and west orientations and a different type of low-e (a hard-coat low-e, such as LOF's Energy Advantage) for the south windows. The Energy Advantage low-e coating lets through much more of the total solar spectrum, so it fits well with passive solar heating. Many window manufacturers put only one type of low-e glazing in their windows (usually low-e2), but some manufactures will allow substitution.

-Alex Wilson, Editor
Environmental Building News
I'm sure that once the experts get here they will straighten us out. :)


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 Post subject: Low-E
PostPosted: Fri Oct 29, 2004 6:36 am 

Joined: Thu Oct 07, 2004 10:25 am
Posts: 191
Location: East of the Mississippi
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Quick and dirty...

There are two types of Low-E coatings currently available, hardcoat and softcoat.
Hardcoat, also called pyrolitic, consists of a layer of tin oxide applied to the top side of the glass during the float process.
Hardcoat is durable and can be used on either the inside or the outside of an IGU. Generally, hardcoat is applied to the #3 surface for cold weather applications. I can explain that in much more detail if anyone is curious.

Softcoat, or sputter coat, is applied in a vacuum chamber after the glass has been shipped from the float glass factory.
Softcoat consists of several microscopically thin layers of various metals and metal oxides applied to the glass. The "working" part of a sputter coat is silver.
"Regular" Low-E has a single layer of silver. Low-E2 (actually squared) has two coats of silver in the mix. Low-E2 is Cardinal's brand name for their advanced Low-E coating. It is also used somewhat generically for other advanced coatings simply because Cardinal supplies something close to 75% of all residential Low-E now used.

And yes, it really is that much better than the original Low-E...
And, both of the above quotes are actually correct...but I found that I had to reread them a couple of times to follow what they were saying. Not that MY posts are always easy to follow! :wink:

Hope this helps.


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 Post subject:
PostPosted: Fri Oct 29, 2004 7:53 am 

Joined: Thu Oct 07, 2004 9:26 am
Posts: 67
Location: Atlanta
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I knew the experts would show up! Thanks Oberon.

I hope I didn't hijack Jack's question, and I hope that his question
Quote:
Is it worth upgrading the sashes to it [from lowE to lowE2]?
gets answered.

Okay, experts, when I get my new windows (with lowE2) installed what proves that there is lowE2 in/on them? You all educated me that having safety glass is identified by some sort of a bug etching on the glass. Is there something similar for lowE or lowE2? Or is it listed on the manufacturer's label/sticker? Or do I have to trust the dealer? Or what?


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 Post subject: Low E verus Low E2
PostPosted: Fri Oct 29, 2004 8:34 am 

Joined: Thu Oct 28, 2004 7:24 am
Posts: 5
Location: Reston, VA
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Hi Guys,
Thank you for the excellent information.

It's not worth upgrading my sashes unless the U value shows a sigificant difference. Maybe I will wait until they add heat mirror too.

Thanks very much,


Jack


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 Post subject: Heat Mirror
PostPosted: Fri Oct 29, 2004 9:29 am 

Joined: Thu Oct 07, 2004 10:25 am
Posts: 191
Location: East of the Mississippi
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Heat mirror is an interesting product. It is manufactured by Southwall Technologies from an idea developed at MIT back in the late 60's early 70's.
Basically, it is a sheet of PET film suspended within the IGU with a coating on the PET. The energy numbers for Heat Mirror are truly remarkable.
But, there is a downside. Unfortunately, the CoE (Coefficient of Expansion) between glass and PET film is not really very similar.
There is quite a number of stories floating around that Heat Mirror has been plagued with PET film wrinkling and seal problems. I know that there are many satisfied Heat Mirror customers out there, but I admit I have yet to meet one.
Just an observation.

And how does one tell that their new windows actually have Low-E glass?
Several ways...
The easiest is to hold a lighter (or other open flame) near the glass and look at the reflection in the window. If you have Low-E, and it is on the #2 or the inside of the exterior lite surface, then you will see three flames reflected in the glass. If you are doing this test from the inside of your house, the two "flames" farthest from you will be close together and then a space and then the third flame.
If you perform this test outside, there will be two flames close to you and then a gap and one flame further away.
The center flame will be a slightly different color than the two flames that bracket it.
It is best to do this test in the dark, although you can do it in daylight as well. It is simply easier to see it in the dark.
The middle flame will be the reflection from the Low-E coating.


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 Post subject:
PostPosted: Fri Oct 29, 2004 6:32 pm 

Joined: Thu Oct 07, 2004 9:26 am
Posts: 67
Location: Atlanta
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Oberon,

I assume that your flame test is for triple pane. If that is correct, then what is the flame test for double pane?

Thanks


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 Post subject:
PostPosted: Fri Oct 29, 2004 8:56 pm 

Joined: Thu Oct 07, 2004 10:25 am
Posts: 191
Location: East of the Mississippi
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Actually Mark, that is double pane. The three flames are the two lites and the Low-E on the inside of one of the lites.
Triple pane would be 5 flames...three for the lites and two (assuming two Low-E coatings) for the coatings.


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 Post subject:
PostPosted: Tue Aug 07, 2007 5:26 pm 

Joined: Tue Aug 07, 2007 1:51 pm
Posts: 3
Location: Granby Colorado
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Quite true about the SHGC:Solar Heat Gain Coefficient
Window standards are now moving away from use of shading coefficient to solar heat gain coefficient (SHGC), which is defined as that fraction of incident solar radiation that actually enters a building through the window assembly as heat gain. The SHGC is influenced by all the same factors as the SC, but since it can be applied to the entire window assembly, the SHGC is also affected by shading from the frame as well as the ratio of glazing and frame. The solar heat gain coefficient is expressed as a dimensionless number from 0 to 1. A high coefficient signifies high heat gain, while a low coefficient means low heat gain. Typical SHGC values for the whole window unit and center of glass are shown in Figure 2-10.

This comes from University of Minnesota.

The term "better" is relative to each situation. If you are trying to gain heat, it would be better using a SHGC as high as possible. If you are trying to block heat gain, it is better to use a window with SHGC as low as possible. It would be "better" to use a different word, related to the desired outcome. 8)

Check out: http://www.commercialwindows.umn.edu/issues_energy2.php


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 Post subject:
PostPosted: Tue Aug 07, 2007 9:15 pm 

Joined: Tue Jan 04, 2005 5:06 pm
Posts: 508
Location: Kentucky
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I do not want Oberon on my back but the newest available lowE is LowE3.

Check out cardinal industries 366 product. Another product is AFG TIAC40.


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 Post subject:
PostPosted: Fri Aug 10, 2007 1:30 pm 

Joined: Sun Aug 05, 2007 11:45 am
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JScott wrote:
I do not want Oberon on my back but the newest available lowE is LowE3.


Some manufacturers in California are already providing lowE3 as standard in their windows.


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 Post subject:
PostPosted: Sat Aug 11, 2007 10:14 pm 

Joined: Thu Oct 07, 2004 10:25 am
Posts: 191
Location: East of the Mississippi
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JScott, I admit that I don't find the image of me on your back all that appealing - :shock: - so no worries there!!! :wink:

Concerning LowE3 and various conterparts, as some of the old-timers may recall (likely not!) I did drop a hint in a post a long time ago just a little bit before any of the new coating had been released yet to watch for them - nothing specific at the time - just a quick comment on the new generation of LowE coatings.

Both Cardinal's 366, and AFG's TIAC40, and the various versions of PPG's SolarBan70, and Guardian's version (that I can't seem to remember what it's called off the top-of-my-head) are triple layer products. In the case of all of them, except AFG TIAC40, that means three layers of silver.

The AFG TIAC40 is really interesting in that it is a sputtercoat that uses titanium rather than silver as the active "low-emissivity" part of the coating. AFG states in their literature that their AFG TIAC40 has the best overall performance numbers of any solar-heat blocking coating - which isn't actually true - but I won't go into it.

One nice thing about how Cardinal names their coatings is that it is easy to understand - LoE-366 simply means 3 layers of silver and 66% light transmittance. LoE-272 means 2 layers of silver and 72% VT. LoE-178 means one layer of silver and 78% transmittance. It would take a heck of a lot less memory cells if the other folks would come up with a similar system! :idea:

Solarmax,

If your comments about using the word "better" as being incorrect when describing softcoat LowE versus hardcoat LowE, were directed at my original post, then I stand by my choice of the word "better".

Softcoats are better than hardcoats in the context of my original post at doing what LowE coatings are designed to do - which is to block heat transfer.

At the time I didn't differentiate between near or far infrared or between direct solar gain or indirect gain in my original post. Simply, as intended, in direct product comparisons between the two primary types of coatings, the softcoat LowE coatings block heat transfer better than do the hardcoat LowE coatings. Specifics between various types of hardcoats and softcoats would take longer to explain but may be worth exploring.

There are now harcoat LowE coatings that have excellent solar heat blocking abilities - hardcoats designed for use in cooling dominated climates.


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