Filling your home or space with windows is always a wonderful addition, allowing natural light and fresh air into your space. However, glass windows, of course, are not the most soundproof. And there are times that in addition to sound, you may prefer that air and light aren’t able to enter your room, so you’re thinking of using a window plug.

Window plugs are easy to make by layering thin boards, a soundproof mat, and acoustic foam. Simply measure your window space, cut and glue the materials together, and insert them into your window.

Making your own window plug is an extremely cost-effective project, especially when you compare the cost to soundproof windows. For a more detailed step-by-step guide to creating a window plug, feel free to follow along. By following these steps, you will have created an effective window plug to soundproof your space.

Consider Purpose, Style, and Size of Window

Before you start making your window plug, it is important to determine what the purpose of the window plug will be. In addition to the purpose of the window plug, what is the purpose of the window? Fortunately, window plugs can be made to be removable, so they will not permanently affect the purpose of the window.

When considering the purpose of the window, the obvious benefits and purpose are likely the light and air it allows into your space. And the purpose of the window plug may be to lessen the sound of traffic outside of your home. Adding a handle to make your window plug easily removable and also will still allow air and light into your home, but when you need to stop sound pollution, the plug can be inserted.

The style and size of the window will also affect the type of plug you want to make. Familiarize yourself with your windows, whether they are flush against the wall or have a shallow or deep window sill. These things will all lead you to make some adjustments as you make your window plug.

A window plug will change the appearance of a room. But there are ways you can make it more visually appealing that will be discussed later in the article.

Measure Window

There are a few different measurements you will want to get from your window before you start shopping for materials. Of course, it is essential to know both the width and height of your window. You will also need to know the depth of the window to determine the thickness of your window plug. Measure from the window to the edge of the sill to get your depth measurement.

It is important to note and your window plug will not press up against the window. You will want to leave one to two inches of space between the window and the plug. So if your window to the edge of the sill measures 5 in (12.7 cm) deep, your window plug will be between 3 and 4 in (7.8 and 10.16 cm). This “dead space” will give soundwaves space to ricochet and ultimately cancel themselves out.

Unlike the depth, the width and height measurements will be the exact measurements you will want to use when cutting materials for your window plug. The plug must fit airtight into the window for the highest performance.

Gather Tools and Materials

You will need some handheld tools to get this project started. You will also need to purchase the materials needed to create the window plug. Luckily, not many tools or materials are required for this easy project. Everything you need will be easily found at any hardware store or ordered online.

The tools you will need are:

  • A tape measure
  • A saw
  • A level
  • A square
  • A utility knife
  • A drill and screws if choosing to attach handles
  • Caulking gun, depending on the type of glue you choose to use

As far as the materials you will need, you will have a few options. Your budget plus how effective you want your window plug to be will help you determine what materials will work best for your specific project. You will be looking for three different types of materials to create the three layers of your window plug.

The soundproof materials you will need are:

  • Wooden board
  • Soundproof Mat
  • Acoustic foam

Other materials you may need include:

  • Spray adhesive or bond of choice
  • Pull handles, if creating a removable window plug
  • Fabric if you want to make the appearance of the plug more appealing

Higher density materials are going to be higher performing when it comes to soundproofing. For instance, a medium-density fiberboard (MDF) is a heavier material that will block soundwaves more effectively than a piece of plywood will. However, plywood is a more budget-friendly option and would still do the trick.

When looking for a soundproof mat, mass loaded vinyl (MLV) seems to be the highest-performing material. MLV damps or reflects the sound before it has the chance to build up. For acoustic foam, neoprene foam is a common selection. Seek advice and insight from employees of the hardware store as you select your materials.

Making a Window Plug: A Step-by-Step Guide

1. Cut the Board

Draw the width and height measurements on your piece of plywood or MDF, remembering these should be the exact measurements as the window to create the tightest fit. Use your square to be sure you get exactly 90° angles. Using a hand saw, or table saw, cut the MDF to size.

Once the board is cut, it may be helpful to ensure a tight fit into the window well by inserting the board into the window. Using your handheld level will also help you be sure you are cutting the board as straight as possible.

2. Cut the Soundproof Mat

Repeat the cutting process on your soundproof mat. Again, this is commonly the mass loaded vinyl or MLV. Another option could be fiberglass panels. Draw the width and height measurements using your square tool and cut the mat with a hand or table saw. Again, insert the mat into the window, ensuring accurate measurements and a tight fit.

3. Cut the Acoustic Foam

When you cut the acoustic foam, you will use different tools and cut the size a bit differently. The foam will be easily cut with a utility knife or even scissors. Using a saw will not be necessary.

Add an inch to both the width and height. Cutting the acoustic foam an inch larger than the window itself will create the tightest fit into the window. The foam will also account for any asymmetries in the window framing. The foam is made of flexible material, allowing it to be pushed into the window opening. The foam will fill up the window well, creating a seal.

4. Glue Materials Together

Once your board, acoustic foam, and soundproof mat are all cut to size, you can start to assemble the layers of the plug. You can use spray adhesive or any sort of bond to secure layers together. For even more security, you can use a staple gun or nails and go around the edges of the plug.

When looking for an adhesive, know that there are soundproof sealants and glue that would help reduce the sound even more. Again, consider your budget, and if you have the means, using a soundproofing sealant will lead to the best results.

After gluing the materials together, double-check the final depth measure of your window plug. Remember that it should be 1 to 2 inches (2.54 to 5.08 cm) less than the depth of the window well to allow for dead space for the soundwaves to dissipate.

If your window plug will leave more than two inches of dead space, add more layers to your plug. The easiest way to do this is to another layer or two of MDF. As mentioned earlier, MDF is the highest performing material but not the most budget-friendly. A good trick for adding more layers to the window plug would be using layers of plywood under the MDF to save more money. The more layers your window plug has will create an even more effective plug.

5. Cover Plug-In Fabric

This step is optional. However, one disadvantage of putting a window plug into your window is that they are not necessarily attractive. When already blocking out natural light and covering the source with pieced together boards, you may wish to add some sort of visual appeal to the window plug.

Many people choose a fabric to match their room or space and cover the plug with fabric. You can do this simply by measuring the fabric a few inches longer than the plug, wrapping it around the plug, and using a staple gun to secure the fabric.

If the window plug is a more permanent solution, some people even choose to cover it with a piece of art or even hang soundproof curtains over the plug.

6. Add Handles

This step is also optional, but it may help with the functionality of your window plug. If you want your window plug to be removable, you can add handles to it. This will make the removal of the window plug much easier.

Before going on to the next step of inserting the window plug, take note that the layer of foam will be the layer that is inserted closest to the glass window pane.

7. Insert Plug Into Window

After constructing your window plug, it will be time to insert it into the window well. To do this, you will simply be pushing the plug into the wall. You will not need any tools, nor will you use anything to secure the plug. It should create a tight seal on its own. A recommendation is that you use weatherstripping tape along the window frame to create an even tighter seal.

Once the plug is inserted, if you notice the sound is still coming through the window, you can cover the window with a single layer of MLV. Also, if you become concerned about the security of the window plug as they are quite heavy, you can secure the plug by putting a bungee cord across the window plug for better security.

Advantages and Disadvantages of Window Plugs

Advantages of soundproofing windows are obvious if you live in a high traffic area and have young children, an office space, or even some sort of home studio. Now that you know how to create a window plug, here are some advantages and disadvantages you may or may not have already considered.


  • Significantly reduce sound transmission into and out of a room
  • Seal gaps around the window, which can assist thermal energy efficiency
  • In addition to sound, the window plus blocks light from getting into your room. This could be beneficial if you have children, work a shift job, or live in an area with an active nightlife.
  • Significantly more cost-effective than soundproofing window or installing additional windows


  • If not using the highest-performing materials, window plugs may not be able to block out low-frequency sounds
  • Window plugs are large and are difficult to remove, move, and store
  • Can affect the purpose of the window, like getting fresh air and natural light
  • During the summer, the room will get incredibly hot

Final Thoughts

Of course, windows come with many benefits, such as filling your space with natural light and fresh air. However, without windows being soundproof, there can be some disadvantages. Building your own window plug is a relatively easy and extremely cost-effective do-it-yourself project. Hopefully, this step-by-step guide will help you as you tackle your project to soundproof your space.

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