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How to Soundproof a Window

How to Soundproof Windows

How to Soundproof Windows

Soundproofing a room is a lot easier if you don’t have any holes in the walls. No windows… no doors… just you, entombed with your state-of-the-art sound system in a single dark room. While isolating yourself in a sealed off room to listen to your favorite album might sound enticing (raise your hand if you have kids), it’s not the most practical approach. A room needs windows! We need light, airflow, a place to set an apple pie when it’s fresh out of the oven.

Unfortunately as much as I love rooms with lots of windows to let in more light, windows (and doors) are also the weakest point in your walls for blocking sound. If you’re having issues with outside noise from traffic, nearby construction, or noisy neighbors, improving the soundproofing of your windows can be a game changer.

Let’s break down the different parts of a window, talk about the keys to soundproofing, and give some guidance on how to actually soundproof your window.

Soundproofing a room is a lot easier if you don’t have any holes in the walls. No windows… no doors… just you, entombed with your state-of-the-art sound system in a single dark room. While isolating yourself in a sealed off room to listen to your favorite album might sound enticing (raise your hand if you have kids), it’s not the most practical approach. A room needs windows! We need light, airflow, a place to set an apple pie when it’s fresh out of the oven.

Unfortunately as much as I love rooms with lots of windows to let in more light, windows (and doors) are also the weakest point in your walls for blocking sound. If you’re having issues with outside noise from traffic, nearby construction, or noisy neighbors, improving the soundproofing of your windows can be a game changer.

Let’s break down the different parts of a window, talk about the keys to soundproofing, and give some guidance on how to actually soundproof your window.

Overview of the Parts of a Window

Part Description
Frame
This exactly what you think. The construction that surrounds the window. The frame includes the head, jamb, and sill.
Head
The top part of the frame that runs horizontally.
Jamb
The sides of the frame that run vertically.
Sill
The bottom of the window frame that often creates a small ledge.
Sash
This is the construction that holds the window panes and can move up and down
Rails
These are the horizontal pieces that make up the sash. On a double-hung window, there is an upper rail, lower rail, and a check rail where the two sashes meet in the middle.
Stiles
Like rails, stiles are part of the sash, but they are the vertical pieces.
Grilles
This is usually just a decorative piece that creates a grid on the window to give the appearance of multiple window panes.
Glass
This is… the glass part.

Keys to a Soundproof Window

Now that you’re fully acquainted with all the pieces and part of a window, let’s get into what makes a good noise barrier. There are three qualities that every soundproofing project should account for.

Density - More mass makes material more soundproof. A heavy concrete slab will block more sound than a sheet of plywood, which in turn blocks more sound than a sheet of paper.

Limpness - Although this may seem counter intuitive, softer materials also help with soundproofing because they are better at absorbing sound. If you were to bang on an aluminum sheet, the impact would create loud reverberations, compare that to punching a limp bedsheet hanging on a line, which absorbs the impact energy and makes almost no noise.

Airtight - Sound moves like water. It will find a way to leak through any gap available. which is why windows are a weak point for sound. By creating an airtight barrier, there’s no way for sound to move through the structure.

Why are Windows the Weak Point in Your Wall?

Windows are often the weak point in a soundproof wall for two reasons. The first, is that sound will find its way through even the smallest gaps. A 1% air gap will cap the amount of sound that a wall will block at about 20 db. Even a closed window is tricky to seal properly. And then for an open window… the wall is not able to do much.

The second reason is because of how any barrier tends to only be as strong as its weakest point. By introducing glass into a brick wall, the amount of sound blocks decreases from 50 db all the way to 29 db. By the time the wall is half glass, it essentially blocks sound as well as a wall that’s 100% glass.

How to Soundproof a Window

Now that you have a better understanding of how sound barriers work, we can get into how to soundproof a window. It really comes back to building a structure that follows all three of the core features of soundproofing: (1) dense (2) limp (3) airtight – with a few wrinkles thrown in. Let’s get into some strategies you can follow to improve each of these three things in your window construction.

Add mass with thicker or multiple panes

The first way to add block more noise with a window is to increase the thickness of the glass. Go all the way up to ½” to increase mass.

The second way is by adding additional window panes. Having two panes of glass with an air gap between them creates a “double wall” effect, which is the same sound blocking strategy used in wall soundproofing. That’s why single-pane windows block less noise than double-pane windows. Sound Transmission Class (or STC) is used to measure how much sound a partition is able to block, a higher STC rating means more blocked noise. Single-pane windows have an STC rating between 26 and 28, while a double-pane window can have an STC rating in the high 40s. Windows utilizing our Fantastic Frame Window Inserts regularly get up into this range. Air gaps between panes should be at least ½” wide, but more spacing is better. Every time you double the air gap, you’ll reduce the transmitted sound by another 3 decibels.

Increase limpness with laminated glass

If your windows are made using tempered or monolithic glass, laminated glass could give better soundproofing. This is because laminated glass is made with two glass sheets fused with a protective layer of plastic in the middle that adds limpness and damping. A sheet of laminated glass can achieve an STC rating three or more points higher than tempered glass at the same thickness. Damping of laminated glass is reduced by cold weather, so in double glass construction, keep the laminated pane on the side of the window closer to the interior of your home to maximize performance.

install windows to be airtight

Even the most advanced safe in the world is rendered useless if the door is left cracked open. A soundproof door isn't soundproof if it's not closed. Similarly, a window that has gaps or is left open won’t do anything to stop sound. In fact, if a window doesn’t need to be opened, consider sealing it completely closed. Sealed windows can have an STC rating 3 to 5 points higher than a normal window.

If you don’t want to seal your windows completely shut there are two ways to improve the installation of your windows so they let in less air and sound.

Acoustic caulk - Adding acoustic caulk around the frame of your window will prevent sound from flanking through the gaps. Acoustic caulk sealant is an inexpensive and easy way to improve the soundproofing of your window. Acoustic caulk is more flexible than silicone which means it won’t shrink or form cracks over time. It’s also extremely durable and can go several years without the need for re-caulking. Most acoustic caulk is white, but some can come in a variety of colors including clear, all of which can always be painted over to the color of your choice.

To apply acoustic caulk, start by removing the existing caulk around a window. A putty knife is a great tool for this, do your best to get all the debris out so the acoustic caulk can be applied smoothly and bond evenly. Cut a quarter-inch opening opening in the caulk tube and load into the caulk gun. Apply the caulk as a full, even bead in the gap between the window frame and the wall by keeping a constant pressure on the trigger. Smooth out the caulk you applied with a caulk tool or your finger.

Upgrade your window - There are two ways you can upgrade your windows. One is replacing the window entirely, which can be expensive and time-consuming depending on how many windows you have. Another way is by utilizing window inserts like our Fantastic Frame Window Inserts. These are a cheaper and highly-effective solution to soundproofing compared to completely replacing your windows. These inserts use high-performance rubber mounts to dampen sound vibrations and exterior grade PVC for durability and strength. Window inserts are half the weight of glass and can actually provide even greater noise-reduction than double-pane windows, up to 80% sound reduction and an STC rating as high as 50. In addition to huge soundproofing benefits, window inserts also help save on your energy bill due to the airtight seal they create. The final result: huge reductions in sound and heat transfer that you won’t even notice is there after the inserts are installed.

Soundproof curtains

If for some reason you’re unable to install window inserts, you’ll see some benefit from soundproof curtains. Despite the name, soundproof curtains aren’t actually soundproof and won’t be as effective as the other options we discussed, but they can still block some sound. When choosing curtains, remember to keep in mind the three keys to soundproofing; density, limpness, and airtight installation. It’s tough to make curtains airtight, but you can improve the effectiveness by making sure they cover the entire window and then some.

Similar to a soundproof blanket, soundproof curtains are fairly cheap and easy to install, but they need to be completely closed over the window to provide effective sound blocking. Soundproof curtains are usually made of thick, heavy fabrics like velvet with vinyl linings to absorb sound and reduce echoes in a room. Soundproof curtains are best suited for smaller noise problems, where you just want a modest reduction in sound.

Contact us for a custom soundproofing gameplan

You’re only as strong as your weakest link, and when it comes to soundproofing, that is almost certainly your windows. Luckily you don’t have to resort to bricking up every window in the house to block out the annoying noises outside your home. Depending on where you live, when your home was built, and the type of construction, you may have different windows with unique sound problems. Give us a call and we’ll help you build a plan to tackle any soundproofing problems.