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We are experiencing cold winters.

  1. Just curious if window Low-E tinting (or others options) on actual windows help with heat insulation or if it's just a gimmick. I am referring to actual film (seen in commercial buildings), and not plastic wrap home insulation kits.

  2. If window tinting is so good for heat insulation, how come window manufacturers don't have Low-E built by default?

We are in a residential complex, and looking into Window tinting technology.

https://www.thespruce.com/energy-saving-low-emissivity-film-1821588

https://www.buildings.com/articles/31395/new-low-e-glass-or-window-film-comparison-help-you-decide

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  • here is one product claiming to do this, solar gard spec sheets solargard.com/wp-content/uploads/2019/01/…
    – mattsmith5
    Dec 10, 2021 at 2:53
  • another one, claiming to do same missouriglass.com/blog/how-to-insulate-windows-for-winter
    – mattsmith5
    Dec 10, 2021 at 2:57
  • One factor you might want to consider is that both proper low-E coatings (to a lesser extent) and any sort of film you apply reduce the visible light transmission (i.e. the primary reason we have windows at all.) Some sort of mirror film might successfully reflect heat, but it's also going to cut the light level significantly.
    – Ecnerwal
    Dec 10, 2021 at 3:51
  • Window tinting? Go for triple-glazing, that makes a difference
    – Solar Mike
    Dec 10, 2021 at 6:47
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    This is precisely why SE expects one question per post! You've got a great answer to your first question and a great answer to your second question, they're just not in the same answer box. I'm VtC as too broad - edit it down to one question, and ask the second one separately where the excellent answer for it can be copy/pasted.
    – FreeMan
    Dec 10, 2021 at 12:55

3 Answers 3

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As to your second question, window manufacturers don't build in low-e by default because they typically sell it as an added-cost option, though in some markets regulations effectively require some form of low-E for windows to be sold, or at least installed in new construction. There are still more and less expensive versions. So your windows might indeed already be some type of low-E, depending on the market and age of the building.

Those manufacturer coatings are (AFAIK exclusively) applied to the "sealed side" of the panes in multi-pane sealed window units, not stuck on the outer face. They are usually not attempting to be noticeably tinted as such - but they often are somewhat tinted if directly compared to a clear glass window (which are often themselves very slightly green unless low-iron glass is used.)

Different coatings perform differently. I live in a primary-heating climate, but window regulations had been (too) broadly applied in such a way that I was looking at 3x the cost to get windows coated to optimize heat collection and keeping heat in, (a high Solar Heat Gain Coefficient) rather than windows optimized primarily for keeping heat out (a low Solar Heat Gain Coefficient.) Budget not being infinite, I have windows that are better for A/C which I rarely use, because the payback on triple the cost and the hassle of importing them was not worth it. They keep heat in better than uncoated windows, but they minimize the extent to which the sun helps heat the house, which is a benefit more often than not where I am.

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  • you know , my window is already tinted green, I wonder if it already has low-e
    – mattsmith5
    Dec 10, 2021 at 5:45
  • Thanks, also can you answer the first question? I am in around 45-50 degrees mild winters in california, curious if the low-e coating tint will have noticeable affects, or only works in much colder temperatures
    – mattsmith5
    Dec 10, 2021 at 5:46
  • on a triple glazed unit, you have low-e coatings on surface 2 and 5. the double glaze low-e panels have it on surface 2 and 4 (interior exposed side) - you can damage it by scrubbing / handling the interior side. Dec 10, 2021 at 7:59
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    @mattsmith5 this is precisely why SE expects one question per post! You've got a great answer to your first question and a great answer to your second question, they're just not in the same answer box.
    – FreeMan
    Dec 10, 2021 at 12:54
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"SolarGard and 3M claim Low E help during the winter." - of course they do; they sell windows. But which one do you want for your climate?

https://www.nachi.org/low-e-windows.htm

Windows with high solar-gain low-E glass are designed to reduce heat loss while admitting maximum solar heat gain. They are best used in heating-dominated climates, especially for passive-solar design projects. They usually incorporate an argon gas-fill, and the glass is typically made with a pyrolytic low-E coating.

Windows with medium solar-gain low-E glass are often referred to as spectrally selective, and they reduce heat loss while allowing a moderate amount of solar heat gain. They typically use an argon gas-fill. They are usually made with sputtered low-E coatings.

Low solar-gain low-E glass is also spectrally selective and is best suited to cooling-dominated climates, where the biggest concern for windows is blocking heat transmission. These windows are made with sputtered low-E coatings that consist of either two or three layers of silver. They are sometimes called double-silver or triple-silver low-E windows.


Also, I took the liberty of fixing their plug:

'Low emissivity prevents heat from escaping through windows while keeping out 52% of the sun’s energy.'

"Low emissivity prevents heat from escaping through windows in the Winter. Spectral selectivity lets in 68% of natural light while keeping out 52% of the sun’s energy."

So I can't really answer the question, other than what logic dictates the "biggest concern for windows" is.

52% loss on solar gain vs 'emissivity'. Whatever that computes to.


According to some utility company, yes. And it's climate dependent for which side and which piece of glass should be coated.

http://www.energydepot.com/RPUcom/library/BUILD001.asp

A double-pane window with a low-E coating will have an R- value equivalent to or better than a triple-pane window. Windows in warm climates, where cooling is the primary concern, should have the low-E coating on surface 2 as shown in the figure below. In cold climates the coating should be on surface 3.

enter image description here

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  • You can't laud something for working in the winter if you live in Florida.
    – Mazura
    Dec 10, 2021 at 9:43
  • Presumably when given the average climate, for which at a given temperature differential, it's better to have as low emissivity as possible because the SG is negligible in comparison at that deferential. I'm guessing if you live at -10 and keep your house at 80; you can forget SG. But that's counter to what nachi says above. - The ad says "prevents heat from escaping through windows" if that means +.01 R-value then SG wins by orders of magnitude.
    – Mazura
    Dec 10, 2021 at 9:57
  • I feel like this still comes up short. But you either want sunlight in, out, or both. Maybe 'emissivity' is the gimmick. And that just happens when you add coatings to glass. The gas is the important part.
    – Mazura
    Dec 10, 2021 at 10:02
  • "looking into Window tinting technology" - nope. It goes on the inside, #2 or #3; don't matter where you live. Full disclosure : read the title; never even clicked those links.
    – Mazura
    Dec 10, 2021 at 10:24
  • I live in California, my place is fine during the summers, it gets kind of chilly during the winter, 45-50, but nothing bad compared to other places : ), I was thinking of getting curtains, but was researching into film/tints for winter
    – mattsmith5
    Dec 10, 2021 at 16:42
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Tinting is not going to provide much insulation - it is, at best, a thin layer of plastic directly attached to the window. What it can do very well is to cut down on heating from sunlight in the summer. If it is properly designed, low-emissivity films can help keep heat inside during the winter as well, but this is a different process (reflection) than insulation.

Plastic wrap insulation kits provide very little (practically speaking, none at all) insulation from the plastic. The insulation is the dead air in between the plastic and the window glass. There is no space between a tint wrap and the glass, therefore no substantive insulation.

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  • I got this info from here, I see a LOT of companies like this, with high Yelp and Google reviews, not sure, sunsafewindowfilms.com/commercial. "Installing window tint is a smart way to lower energy costs and reduce CO2 emissions. Watch the numbers drop on those HVAC costs with the installation of window tint, which can keep out up to 86% of the sun’s heat, dramatically lowering air conditioning costs. In the winter, the same film helps retain interior heat, reducing your heating costs. They may also help you attain LEED credits in getting your building closer to certification."
    – mattsmith5
    Dec 10, 2021 at 2:05
  • not sure what to think at this point, lot of the vendors I called claimed to help Commercial buildings with their heating costs in winter
    – mattsmith5
    Dec 10, 2021 at 2:07
  • I'm dubious (but there could be some truth to it) about it helping much with heating during the winter. But helping keep the building cooler in the summer, definitely. Dec 10, 2021 at 2:11
  • to bring in a specific product I was hearing about from vendors for winter protection , solargard.com/product/ecolux, here is the pdf solargard.com/wp-content/uploads/2019/01/….
    – mattsmith5
    Dec 10, 2021 at 2:39
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    I will add that the plastic wrap insulation kits with air space between the plastic and insulation definitely do provide a surprising amount of insulation. It's implied by this answer, but I thought I would remove any doubt. Dec 10, 2021 at 11:03

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