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how to soundproof windows

Noisy roads, loud neighbors, and nearby industrial activity can produce painfully high sound levels that pass right through your windows. However, there are several relatively easy methods available to DIY’ers to soundproof windows.

How to Soundproof Windows Effectively

Applying double glazing or adding extra layers of glass is the best way to soundproof windows. Inexpensive alternatives include window plug, seals, storm windows, and soundproof curtains.

Well, that was the short answer.

 Based on experience and research, here are 7 effective ways to soundproof windows:

  • Double Glazing
  • Build a Window Plug
  • Seal the Air Gaps
  • Add Soundproof Curtains
  • Install a Quilted Fiberglass Panel
  • Add Storm Windows
  • Add An Extra Layer Over the Glass

Each method has its benefits and drawbacks, but all are effective, particularly when used in combination. Let’s discuss what’s involved so that homeowners can make an informed decision and finally get some sleep!

1. Double Glazing

Double glazing offers the best insulation but the main concern is with the cost involved. Double glazing windows involve fitting the window frames with two panes of glass leaving a spacing of 12mm – 16mm in between.

Double glazing cross section

The space between the frames and panes is sealed to make it airtight and the dead air in between acts as a very effective insulating area. 

Below is a chart which compares the soundproofing effectiveness in terms of STC (Sound Transmission Class) of normal single pane, laminated and double glazed windows.

Soundproofing capability – Single pane vs Laminated vs Double glazed windows

The mean values of STC of the three types are as shown below. The effect of each STC value is given in brackets as per information from Wikipedia.

  • Single pane windows: Mean STC 30 (Loud speech can be understood)
  • Laminated windows: Mean STC 35 (Loud speech audible but not intelligible)
  • Double glazed windows: Mean STC 41 (Loud speech audible as a murmur)

As you can see, double glazed windows make a huge difference but as mentioned earlier, they cost a lot. Let’s look at some cheaper options.

2. Build a Window Plug

This is by far the simplest answer to the problem of window noise. Window plugs are easy to build, are made from inexpensive materials, and are highly effective.

They work by filling in the space in front of your windows with layers of acoustic foam, soundproof matting, and wood. The foam at the front absorbs incoming sound waves.

Any noise that makes it through the foam is blocked by the mat and the wood backer board. Handles are added to the back surface of the wood to allow easy installation and removal.

A window plug is a cheap way to soundproof windows

Plugs have the advantage that they aren’t permanent. They can be added when needed and pull out when not. And that’s good because they do have some significant disadvantages.

For one, they aren’t particularly attractive, either from the inside of the house or from the street. Plus they block all incoming light. If your noise problem is constant you won’t have the opportunity to remove the plugs, which means you won’t be able to enjoy natural sunlight during the day.

Of course, if you live in an area with significant light pollution at night, the plugs’ light-blocking properties could be a benefit.

To build a window plug you need to first measure the height, width, and depth of your window opening. Make your plug slightly wider and taller than your window opening to ensure a tight seal.

Measure the dimensions of the gap in the window.

The window depth measurement is important because it will determine how thick your plug can be. Remember when computing this thickness to leave at least an inch of space between the plug’s foam and your window glass. That air gap will aid the plug’s ability to block sound.

To build your barrier, cut your acoustic foam, soundproof mat, and wood board (either plywood or MDF works well) to a size slightly taller and wider than your window opening. Then glue the mat to the wood and the foam to the mat. You can screw metal drawer pulls to the back of the wood board to function as handles.

Once the glue is dry, simply press the plug firmly into your window opening, leaving a small gap between the foam and the glass. You’ll notice a dramatic reduction in noise intrusion.

A more detailed way to build a window plug can be found in my article here.

3. Seal the Air Gaps

If you have decent double or triple-paned windows and you’re still noticing excess noise from the outside, you should look to see if you have any significant air gaps around your window that are admitting sound.

To do this properly you should temporarily remove the trim from around your windows. This will give you access to the outside edge of your window frames.

Fill in any cracks, holes or gaps with a quality acoustic sealant. Acoustic sealants are specially designed polymers that fill holes and prevent sound vibrations from propagating through open air.

Pay attention to what you’re doing. It’s important not to apply sealant in places that could affect the normal operation of your windows. This method is also good to use in conjunction with other methods for extra sound protection.

4. Add Soundproof Curtains

Like a window plug, soundproof curtains are fairly easy to install, particularly if you already have existing curtain rods. Because they’re fabric curtains, they’re more attractive than a wood-backed window plug. However, they aren’t nearly as effective at stopping unwanted sound.

Unlike a window plug that both absorbs and blocks noise, curtains can only absorb. This absorbancy is dictated by the thickness of the curtains, the density of the fabric, and whether there’s an inner liner to add layering and extra thickness.

If you’re suffering from heavy noise pollution, sound curtains alone won’t solve your problem, but they can provide a bit of extra protection when used in conjunction with other methods. On top of this added bit of noise absorption, they can make ugly solutions like window plugs more attractive by hiding them behind curtains.

One method for making soundproof curtains more effective is to buy them longer than you need so that you can fold them over to add another layer and increase the thickness of coverage.

Read my detailed article on soundproof curtains.

5. Install a Quilted Fiberglass Panel

To attenuate exterior noise, the thicker and denser the material you use, the better. Curtains are relatively thin. Quilted fiberglass panels are considerably thicker and very dense. A panel that’s four feet wide by eight feet tall and two inches think weighs over twelve pounds!

The weight of the panel is ideal because it tends to lay flat against a window frame when hung with hooks from above. This fixes another failing of curtains. They tend to admit sound at their top and bottom where the curtain folds don’t hold tight to the window.

The panels come with metal reinforced eyelet holes. To hang the panel you can install heavy-duty hooks around your window frame and insert them into the eyelets. To make the panels even more effective you can attach the edges using strong velcro. This makes a tight seal around the outside of the window, admitting even less sound.

While a quilted fiberglass panel is significantly more effective at absorbing sound than sound deadening curtains, it’s less attractive. But again, you can install both, and cover the panel with curtains.

6. Add Storm Windows

If you have wood windows, particularly older, single-pane windows you can strengthen their ability to block noise by installing storm windows in front of them. That extra layer of glass and the air space between the two windows add extra barriers to sound transmission.

This is a more costly fix than some of the other methods on this list and may be outside of some homeowner’s abilities, but the addition can be a worthwhile measure against noise. If your problems are severe enough you might consider contacting a contractor and getting a quote. However, skilled DIYers and the adventurous can certainly do the job.

There is one important caveat. If you have vinyl replacement windows, adding storm windows isn’t recommended. In certain cases, heat can build up between the two windows to a sufficient degree that the vinyl window’s frame can bend, bow, or sag, permanently damaging the window.

7. Add An Extra Layer Over the Glass

Another way to add a layer of protection is to attach an acrylic sheet to your existing window glass. The method isn’t quite as effective as storm windows since you get a smaller air gap between the layers, but it’s still reasonably effective and significantly easier and less expensive.

Make sure you get a thick enough sheet of plexiglass. Thin plexiglass won’t offer much sound protection. Don’t go too thick, however, or the sheet will become too heavy. Something in the neighborhood of ⅜” to ½” thick should work well. Also, use window-grade acrylic. This won’t fade or discolor due to sunlight exposure.

You’ll need to measure the inside of your window frames and then get the plexiglass panels cut to fit. To install, you first need to build a simple metal or wood frame. Build it as deep as your window frame will allow. This creates dead air space between the window and your plexiglass sheet.

Build it slightly taller and wider than your windows so that you can wedge it securely into place. This is preferable to gluing the frame to the window because it can be removed easily in the future.

You’ll then glue strong, thin magnets around the frame and in the matching spots on the plexiglass. These magnets will hold your acrylic sheet in place and allow it to be removed in the event that you need to open the window.

This method is more effective than curtains and fiberglass panels and has the advantage of not blocking your view.

Additional Benefits to Soundproofing Your Windows

Depending on the method or methods you choose you’ll get a reduction in noise pollution along with a host of other benefits.

All of the methods detailed here will help weatherproof and insulate your windows to varying degrees. This means better control of cold air infiltration during the winter and a reduction in heat transfer during the summer. Methods that fully block sunlight, like the window plugs, curtains, and quilted fiberglass panels will block much of the summer sun’s heat, reducing your air conditioning usage.

This sunlight reduction will also protect your valuable from sun bleaching. And as mentioned earlier, if you’re also battling bright exterior lights at night, these blackout options will help with both sound and light pollution.

Your Walls Aren’t the Problem

People that are fighting with heavy noise intrusion often assume that the invading sound is penetrating their home through their walls and windows equally. As a result, they spend time and money soundproofing their walls unnecessarily.

The logic seems sound. Windows represent a small portion of the exterior of your home. The majority of your home’s shell is made up of walls. If sound enters through walls, too, it makes more sense to soundproof these, as you get a bigger bang for your buck. Why waste time on those tiny windows?

But this is a mistake. Research indicates that walls aren’t a significant entry point for noise pollution. The reason is found in their layered construction.

Walls commonly have an exterior wood sheathing covered in a siding material. Behind this is an air gap that’s frequently filled with insulation. That’s covered inside the home by a layer of drywall. These multiple layers of varying materials are effective impediments to and absorbers of exterior noise.

Windows, on the other hand, particularly older, single-pane models do very little to block sound. The thin glass isn’t absorptive and transmits sound readily. Older windows also tend to suffer from cracks, holes, and gaps around their frames that leak air and noise.

If you’re suffering from unwanted sound intrusion, don’t sink money into soundproofing your walls. The benefit likely won’t equal the cost. Focus on your windows first and only modify your walls if your window modifications don’t provide ample relief.

Check the Condition of Your Windows Before Soundproofing

It’s important to fix any major issues before starting with any of these soundproofing projects. If your windows are missing glass panes or if they’re badly cracked or otherwise damaged you should replace them.

Older wood windows that weren’t well maintained may suffer from wood rot and large cracks or holes in their sashes or frames. If the existing damage is significant enough, you should consider replacing these windows with new vinyl replacement windows. Badly damaged windows can’t be soundproofed nearly as effectively as functional windows.

It’s also worth mentioning that replacing old single-pane windows with modern double or triple-pane replacement windows can reduce sound penetration significantly. The extra glass layers, and the air gap between them, deflect sound far better than a single pane of glass.

Of course, new, quality replacement windows are an expensive solution, and they usually require professional installation. If you have the budget, new windows may be all you need to handle your noise problem. If not, read on for less expensive, more DIY-friendly solutions.

Choose Your Method, Block the Noise

You’re sure to reduce outside sound intrusion no matter which method you choose, though some work better than others. You’ll need to balance the severity of your problem with the relative benefits and ease of installation for each method.

For highly problematic sounds, window plugs, storm windows, plexiglass sheets, and full replacement windows are your best options. Quieter noise pollution may be fixed with some of the lighter weight solutions.

You might consider trying the simpler solutions first and only graduate to the more intrusive methods if they’re warranted. And you will always benefit from compounding multiple methods.

Common Questions on Soundproofing a Window

Here are some common questions that you may have regarding soundproofing windows.

What windows are best for soundproofing?

Double glazed windows are the best for soundproofing especially considering they provide a sealed insulated layer of air between the panes.

Are soundproof windows expensive?

The best windows for soundproofing (double glazed) are very expensive as they can cost thousands of dollars.

How can I soundproof my windows cheaply?

Window plugs and soundproof curtains are some of the materials that can help in soundproofing a window cheaply.

Are triple pane windows soundproof?

Triple pane windows are not a good idea from a soundproofing perspective as they would be affected by the triple leaf effect.

Can you soundproof existing Windows without replacing them?

Yes, existing windows can be made soundproof to a considerable extent by using window plugs or soundproof curtains.

Here’s wishing you a quiet home.

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