STC Rated Windows: Double Pane + Indow Insert

STC Rated Windows have been tested to determine how much noise they block. STC (Sound Transmission Class) ratings in general use standard testing methods so you can know the degree to which walls, windows, or other building surfaces block airborne sound. If your interior space is affected by exterior sound, then it’s useful to understand how much various solutions will reduce noise penetration. 

STC Rated Windows explained

What Can Indow Customers Expect?

  • An Acoustic Grade insert placed over a standard double-pane window yields a 42-45 STC*.
  • An STC rating of 42 to 45 means that loud conversation outside the window will be reduced to a murmur or not heard at all.
  • Placing Acoustic Grade Indow window inserts over Standard (non-laminated) double-pane windows yielded a 10-12 dBA reduction (approximately a 50% reduction) in noise passing through the window. 
  • The most noticeable effects are with medium to high range frequencies.
  • The larger the air pocket the better.

*This data is based on an independent analysis conducted by the BCIT (British Columbia Institute of Technology) Centre for Architectural Ecology in a controlled environment with specific variables. (You can download the full study here.). Each home is unique, and will experience varying results. Overall noise reduction depends on the amount of sound penetration through doors, walls, ceilings and other vectors as well as the type of noise penetrating the space. For these reasons Indow does not guarantee an overall noise reduction level for each unique application.

To Understand How Much You Will Benefit, First Assess Your Windows

What kind of window do you have?

triple pane window diagram
Diagram of laminated glass window

TIP: If you are unsure about the number of panes of glass, hold a lighter or match in front of the window and count the flame’s reflections. A pen will work but will not be quite as clear.

Note: if you have double-pane with laminated glass, then the sound dampening results will be minimal. Specialty laminated windows are typically designed for hurricane resistance or sound reduction. Indow does not recommend our product for acoustic reduction over laminated double- or triple-pane windows.

One key question is how much space is available in your window frames? How large of an air pocket can be formed? The larger the air pocket the better for noise reduction.

  • 3” and 6” air pockets were used during independent testing.


Placing Indow Acoustic Grade Inserts over operable single-pane windows will reduce the noise coming through your windows by around 18.9 dBA, which is equivalent to a 70% reduction in the noise transmitted through your windows. We have not yet done formal STC testing for this configuration yet, but we have many happy customers who have experienced profound benefits from increased quiet.