"Double vision" of dual pane glass?

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willimusk
Posts: 6
Joined: Sun May 29, 2005 9:52 am

"Double vision" of dual pane glass?

#1 Post by willimusk » Wed Jun 01, 2005 7:37 pm

I have a large picture window and a view of city lights at night. I've been warned that replacing the single pane glass with double pane can create a "double vision" effect, in which lights look doubled because of reflections between the two panes.

Would the resident experts (or anyone else) please comment on the reality of this effect? Is it something to be concerned about?

I'm considering replacing it with a single pane of LowE2 laminated glass (actually two panes laminated together) instead of dual pane in order to eliminate this possible problem. Would this be a good move? Also, can laminated glass be effective in reducing solar heat gain?

Thanks in advance.

Oberon
Posts: 205
Joined: Thu Oct 07, 2004 10:25 am
Location: East of the Mississippi

double vision

#2 Post by Oberon » Sat Jun 04, 2005 10:38 am

Hi willimusk,

Last question first...laminated glass will stop over 99% of UV rays from entering your home, but laminated glass has about the same energy efficiency numbers as a lite of monolithic glass of the same overall thickness. So the answer to that question would be no.

Placing a LowE coating between the laminated lites does help energy performance numbers, especially SHG, but it isn't quite as good as LowE within an IGU (Insulating Glass Unit). Not all laminated glass manufacturers will place a LowE coating inside their laminated makeup, and of those that do, some have warranty considerations so watch for that.

Any time you are looking through multiple layers of glass you have a chance of a certain amount of distortion. When looking at a window, be it single pane or multipane, you are looking at it in two ways - transmittance - meaning you are looking through the glass and - reflectance - meaning that you are looking at the glass. The various codes and standards affecting window and glass performance do take both of those considerations into, well, consideration.

Will you see double when looking through a dual pane window at the city lights? Maybe...

Generally speaking, you are much more likely to see dual images caused by the dual panes of glass in reflection rather than in transmission. You are much more likely to see a room light on a dark night reflected back to you as a double image (especially at an acute angle) than you are to see the city lights as a double image while looking through the window.

A thought experiment: Imagine that every person who has a dual pane window saw double when looking through their window...imagine the public perception and outcry if that were true.

As a rule, you should not see double when looking at the city lights when looking through a dual pane window. There are occasions when the lights could appear a bit "out of focus" depending on a few variables and you could see a slight ghost image in the right circumstances, but as a rule you should not generally notice a difference between a dual pane and single pane window.

You wouldn't happen to be in South Florida would you? I have heard versions of that question from that part of the country a few times before. Some folks down there seem to think that the introduction of dual pane windows is on a par with floridating the water - communist plot instituted by the devil himself.

Actually, the very worst transmittance and reflectance images I have ever seen were through laminated tempered glass. All tempered glass is distorted to some degree, even if you might not really notice it, but when laminating two lites together you tend to have some significant non-parallel surfaces on the two outer faces of the unit which can cause really interesting distortion patterns. Several laminators will not warranty a tempered laminate for distortion issues, telling customers that if they want tempered laminate, they have to live with the distortion.

willimusk
Posts: 6
Joined: Sun May 29, 2005 9:52 am

#3 Post by willimusk » Sat Jun 04, 2005 11:48 am

Hi Oberon,

Thank you for the thoughtful reply. Sounds like I shouldn't worry too much about the doubling effect. And I think I'll avoid the laminated glass option for the sake of energy-efficiency, and to avoid a geniune risk of visual distortion. This window will have to be tempered, I'm told, because of its size (12 ft x 5 ft).

To answer your question, no, I'm not in Florida; I'm in the SF Bay Area, which itself is thought to be a communist plot in many parts of the country. :lol: The issue was actually raised to me by a rep from a window installation company who, understandably, wanted to protect himself and his company from a potential warranty claim. Apparently, his firm installed a large picture window in SF and received complaints about the distortion I mentioned.

RufusHowell
Posts: 1
Joined: Sun Sep 15, 2013 1:14 am

Re: "Double vision" of dual pane glass?

#4 Post by RufusHowell » Sun Sep 15, 2013 1:03 pm

willimusk wrote:I have a large picture window and a view of city led lights at night. I've been warned that replacing the single pane glass with double pane can create a "double vision" effect, in which lights look doubled because of reflections between the two panes.

Would the resident experts (or anyone else) please comment on the reality of this effect? Is it something to be concerned about?

I'm considering replacing it with a single pane of LowE2 laminated glass (actually two panes laminated together) instead of dual pane in order to eliminate this possible problem. Would this be a good move? Also, can laminated glass be effective in reducing solar heat gain?

Thanks in advance.
Hello friend I am facing similar issue with my large picutre window.. Plenty of light comes inside so can you tell an effective and affordbable way to solve it?Please reply thanks in advance:)

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