Replacement Window GuideNo window blocks sound completely, but the same features that make a window efficient also make it quieter. The NFRC calls minimizing air infiltration the most significant step to reduce sound transmission, and points to laminated glass, wider gaps, and gas fills for the rest. This guide explains what actually cuts noise, with every figure tied to its source.
Air sealing comes first
The NFRC sound guidance states that the most significant step which can be taken to reduce sound transmission is to minimize air infiltration.
The NFRC noise guidance explains why: sound and air pass through the same leaks in a window. Before spending on exotic glass, a tightly sealed window closes the easiest path noise takes into a room.
Multiple panes and gas fills
The NFRC noise guidance states that windows with multiple panes of glass block more sound, in particular if the space between them is filled with an insulating gas such as krypton or argon.
The NFRC sound guidance adds that wide air or gas gaps of five eighths inch or greater, instead of one half inch or less, further reduce sound, and that replacing air with argon or krypton between the glazings helps. More panes, wider gaps, and denser gas all work in the same direction.
Mismatched thickness and laminated glass
Matching pane thickness lets certain sound frequencies pass; mismatching them does not. The NFRC sound guidance describes a one quarter inch exterior light with an inner light of different thickness, often laminated with one eighth or three sixteenths inch glass.
The same guidance lists triple glazing with varying glass thicknesses, including glass greater than one eighth inch thick. Laminated glass and deliberately unequal panes are the specialized steps that push a window toward true noise control.
Reading the air leakage rating for noise
There is no NFRC soundproofing number, but there is a useful proxy. The NFRC noise guidance states that although NFRC does not rate windows for their ability to block sound, its window ratings still provide an accurate measure of soundproofing via the Air Leakage rating.
The NFRC window ratings guide describes Air Leakage as the volume of air that can infiltrate a home through a window, where a lower number means less air leakage. When comparing windows for a noisy location, the lower air leakage figure is the quieter choice.
Efficiency and quiet go together
The overlap is not a coincidence. The NFRC noise guidance notes that efficient windows are prized for energy efficiency and control over comfort, moisture, and natural light, and that those same qualities also provide better soundproofing.
The NFRC noise guidance also notes that using thicker panes with larger gaps between them can help. A window chosen well for energy performance is usually already a step quieter than the single pane it replaces.