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The Case of the Double Pane Window Upgrade

Question Regarding Double Pane Window Upgrade:

Hi Glass Detective,

I’m unsure if my laminated upgrade was properly installed in my residential double pane windows.  My contract says laminated 7/32 over 1/8.  I also was to have installed a pane with low-e coating and argon fill in between the lam and the low-e.

Question #1. Does proper installation of the laminated pane go on the inside? And does it make a difference which thickness goes to inside or outside for superior sound deadening?

Question #2.  Does the low-e pane get installed to the outside?

Thank you,

Greg F.

Answer to Question Regarding Double Pane Window Upgrade:


Thank you for contacting the Glass Detective with your concerns over whether or not the glass that was installed in your home, apparently in an effort to reduce sound, was installed correctly. I am assuming this is your “central/primary concern” based on the information provided and the questions you are asking. What I intend to do is to answer your specific questions while also providing a little more information to you. Here we go… Generally, the use of laminated glass does indeed help reduce sound transmission through glass. There is irrefutable proof of this and I have personally been involved with tests (before and after results) that confirm the benefits of laminated glass for sound transmission reduction. To answer your first question about the placement of the laminated product for best performance in sound reduction, it doesn’t much matter in a typical residential installation. However, I typically prefer that the laminated side be to the interior (in residential applications in particular) because laminated glass is also a safety glass and therefore provides some level of safety benefit in addition to sound reduction.

As for your question about the placement of the “Low-E” coating, this is a little more complicated. We know that “Low-E (low-emissivity)” glass has some true advantages and the popularity and use of these products has grown incredibly over the past several years. “Low-E” glass is produced by applying metallic (metal oxide) layers to a piece of glass that are so fine that it is virtually impossible to see them. Not all “Low-E” coating procedures are the same and there is some variation in the finished product which can cause problems when you are trying to match an existing “Low-E” unit with another one (say during the replacement of a broken piece with a new one that is right next to an old one). It is always advisable to keep your records handy when you have glass installed so that you are able to identify the original source of your glass at a later date. Also, ask your glass supplier for the manufacturer’s identity not only for warranty matters but for future “matching” matters if ever needed.

OK … back to your question about the placement of the Low-E coating. Typically, the placement of the “Low-E” coating to the exterior (what is referred to as the number two surface of an insulating unit) is more effective at reducing “heat gain” through your window because it is going to reflect back out radiant heat (from the sun). Typical placement of the Low-E coating to the inside (what is often called the number three surface of an insulating unit) will reduce radiant heat loss by reflecting some amount of heat back into the interior. So depending on where you live and what your ultimate goal is, the placement of the “Low-E” may be of concern although either way, you will certainly benefit from the use of “Low-E” coated glass.

What the Glass Detective is providing here is a relatively simplistic answer and you may want to talk with your local glass supplier to more fully analyze your situation. Building orientation, as well as shading situations from trees or other buildings and so forth, could all weigh into some of your final decisions. In closing, I truly hope that this information is of some benefit to you. attempts to provide accurate information but cannot be held liable for any information provided or omitted.  You should always work with a licensed, insured and reputable glass shop that can assess your specific needs and local building codes and offer professional services. Never attempt to cut, install, or otherwise work with glass yourself. All content is provided on an informational basis only.

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