Two independent studies have shown how effective Indow inserts are at soundproofing a window. All Indow window insert grades reduce outside noise by at least 50 percent when placed over single-pane windows. Acoustic Grade was specifically designed for soundproofing a window. It reduces outside sound by 70 percent when placed over single-pane windows and by 50 percent when placed over double-panes.*

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Portland State University’s Green Building Research Laboratory Study

Summary of results:

  • Indow Acoustic Grade inserts reduce noise by 18.9 dBA when placed over single-pane windows.
  • Indow Standard Grade inserts reduce noise by 10-12 dBA when placed over single-pane windows.

What was involved in the testing to block sound from windows?

Green Building Research Lab director David Sailor spearheaded the study. His lab researches indoor and urban air quality, air pollution and sustainable buildings.

Indow Standard Grade inserts (⅛” thick) were placed over mock single-pane windows inside a 6’ X 4’ plywood enclosure. White noise was generated inside the box and decibel reduction was compared with and without the insert. Researchers used an Omega HHSL1 sound level meter to measure inside and outside levels.

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Researchers measured the Outdoor-Indoor Level Reduction (OILR) of the single-pane window, then the single-pane + the insert. The difference between the two was the reduction in noise the insert provided to block sound from windows.

This study proved the inserts reduce outside noise and that the thicker, Acoustic Grade, did a superior job. If your primary concern is blocking sound from your window, Acoustic Grade is your best choice.


British Columbia Institute of Technology

Summary of results:

  • Increased the Sound Transmission Class (STC) to 42-45 with inserts over double-pane windows, which is roughly equal to an insulated wall.
  • Average sound insulation improvement of 14dB across frequency bands between 125 and 4k Hz.

What was involved in the testing to block sound from windows?

The Centre for Architectural Ecology/Building Science Graduate Program at the British Columbia Institute of Technology conducted the study. A dedicated facility for applied research and education, it conducts third-party testing of industry products.

Program researchers set up an omnidirectional speaker in a testing facility. Sound intensity measurements were taken with a SINUS Soundbook noise monitoring system, using Samurai software, and a SINUS Type 1 intensity probe. They took baseline tests of the double-pane windows and then tests with the inserts installed at 3” and 6” away from the window glass.


STC Ratings & In-Home Results

Many factors affect how well window inserts reduce noise. You may experience a dramatic reduction in one room while in another it’s less noticeable. Our Soundproofing Your Home articles give an overview of how sound enters a space to help inform your overall noise reduction strategy.

The diagram below shows where Indow inserts fall in the STC rating (Sound Transmission Class). With STC rating, the higher the score, the less noise can penetrate. An insulated wall as a much higher STC rating than a single-pane window. As you can see in the diagram, Indow inserts combined with a single-pane window block noise better than an insulated wall. Read the definition of STC rating.

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*We want to ensure our inserts help solve your noise problem. Overall noise reduction depends on the amount of noise coming through your walls, ceilings, floors, doors, and existing windows. Noise reduction will be less when placed over double-pane windows. Read our full Noise Reduction Sheet to learn more.


Your sales representative can also help by asking questions about your home, as well as the noise affecting you, to determine whether Indow is a good solution for you. Fill out our form for a free consultation.

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What Do They Cost?
Indow Performane Grades start at $39 MSRP per sq ft. That's $468 MSRP for a 3'x4' window opening.*

Consider the cost and distruption of replacing your windows. The national average for a vinyl window is $66-$87 per sq ft and wooden incased windows average $71-$109 per sq ft.

Get a Free Estimate

*Local authorized dealers may charge a measurement and installation fee. Sales tax may apply.

Grade Types

Each grade blocks drafts and reduces outside noises, but our premium grades have special features to make your existing windows work the way they’re designed to while providing additional benefits Click here to read all of our grade descriptions.


We custom make each insert to fit your window frames precisely. Once we have the laser measurements of your window frames, the inserts take two to three weeks to manufacture.

To get a free estimate, contact us today.

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