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Author Topic: Adding an extra interior window to a existing double pane picture windows?  (Read 4892 times)


  • Guest

My living room has 4 large picture windows (windows that don't open) and they allow a lot of street noise into the house. This is a residential street -- but it gets a lot of traffic, including a lot of UPS & FedEx trucks with loud engines as they speed through the neighborhood.

These windows are all at least 25 years old (I've owned this house for 22) and I was thinking of replacing them all with better windows with one thick pane, but after doing some reading have considered adding an additional window instead, on the inside. Since these windows don't open, I don't have to worry about and extra window opening, so it feels like a simpler solution, and maybe better for acoustic insulation? 

I've read a few other posts that a 2" gap is ideal, but I don't have that much space, probably closer to just over an inch.

Curious what things I should think about for this? Should I do more to prove that the windows (and not the walls) are the primary issue with sound coming in? I've been assuming that it is the windows mainly because they take up most of the wall space on the wall facing the street with the worst traffic (I'm on a corner lot).


Randy S

  • Guest

Yes your windows are the weak would be best for 2" gap but at least with 1" you should achieve STC 37 or greater by adding the second pane..try to go thick 3/8" laminated.

Randy S.