How to Build a Generator Quiet Box [2024]

Generators come in handy when there is a power outage or in any situation when you need power and you are far away from a source.

They are great for use in an RV or when camping or even right at home.

Unless you’ve purchased an inverter generator, you know how loud other generators can get.

The constant hum can get pretty annoying and drive you crazy.

So before you throw out your loud generator and waste your hard-earned cash on an inverter generator, let’s discuss ways to quieten your loud generator.

One of the most popular ways is to build a generator quiet box, which can also be used to silence other loud appliances like quiet air compressors.

Stick around as we go through the process step by step on how to build a soundproof generator box.

Products you’ll need when building a generator quiet box

Preparation is key so before we jump into the process, here are all the products you will need before you begin.

Step by step process on how to build a DIY generator enclosure

While it is impossible to completely mute the sound coming from your generator, following this step by step process to build a DIY generator box will quieten the sounds by 50% or more.

1. Measure your generator

Every generator box will be different since generators come in a wide array of shapes and sizes.

So to start, measure your generator using your measuring tape.

You will need to be very careful with the measurements because one wrong measurement can undermine this entire project.

Once you’re sure of your measurements, add a few inches on all sides equally and write them down.

These extra inches are put in to compensate for the fiberboard thickness, the insulation thickness, and the ventilation properties.

Doing so ensures that you do not cut the fiberboard the wrong size.

2. Cut the sides and top of the generator silencer box

Now that you have measured and written down the measurements, it’s time to put your saw to work.

Again make sure that you are sure of your measurements before you cut your fiberboard, I cannot stress this enough.

Measure twice or thrice if you have to.

After that, take your right angle ruler and pencil and label the measurements on your 4 wall pieces and single top piece of fiberboard.

Only after doing that should you commence the cutting of the fiberboard.

Some people also use regular plywood but it is less effective than fiberboard.

But if plywood is all you have then go ahead.

use fiberboards to build your DIY generator enclosure.

The Grafix medium weight chipboard sheets come in a pack of 25 with each sheet measuring 12×12 inches and 1.5mm in thickness.

They are easy to work with and are environmentally safe to use anywhere in and around your home.

These chipboard sheets are plain and come in their natural brown color so you can paint them to freshen up their look if you wish.

3. Making holes for Ventilation

Take your ventilation duct and measure its diameter and mark two circles on the board to be cut.

The first hole should be placed on the fiberboard that is to go on the top of your quiet box.

Place this hole more to the side of the top piece instead of the center.

The second hole should be placed on one of the 4 wall pieces.

Placed this hole on the opposite side of the hole in the top piece of the fiberboard.

Once you have finished marking your ventilation hole location, lay everything out on your flat work surface.

The four walls should be surrounding the top piece.

Another benefit of these ventilation holes is that they offer a space for your hands if you want to move your generator box thereby making it a portable generator quiet box.

4. Applying the first layer of insulation

Layering the essential in soundproofing and works by allowing sound to dissipate.

To minimize sound inside of your generator noise reduction box is to add multiple layers of sound deadening material.

Look for material with a high STC rating.

The first one we choose to line the generator box with is mass loaded vinyl(MLV).

Again, you will have to bring out your measuring tape and do some measurements.

Measure the pieces of fiberboard and then apply those measurements to the mass loaded vinyl before you cut.

Cut the mass loaded vinyl to size using a utility knife or heavy-duty scissors.

Attach the cut pieces to the inside of the fiberboards using glue or the acoustic caulk for an even better chance at dampening sounds.

  • STC rating of 27
  • Extruded virgin material
  • Odorless

Trademark soundproofing store TMS MLV has an STC rating of 27 when hanging by itself.

Combine it with the soundproofing properties of the fiberboards and you can effectively block out unwanted sounds from traveling through the air.

This specific MLV is made from 100% extruded virgin material which means no recycled or regrind material was used in the process.

What this means is that you get a super strong and super durable product that will last you for a long time before you have to replace it.

It also means the material virtually has no odor and is safe to be used around humans and pets.

This high-quality vinyl barrier weighs 1 pound per square foot and acts as a 1 pound barrier between the noise and your ear.

5. Using acoustic caulk

Acoustic caulk like Green Glue is different from the regular caulk.

Regular caulk hardens, cracks and breaks over time while acoustic caulk never hardens and remains flexible over time.

Acoustic caulk is better to use in soundproofing since it lasts longer and they come with acoustic properties as well.

Even if you used glue to attach your MLV to the wall pieces of fiberboards, you will need some Green Glue to seal the edges properly.

The edges can prove to be a bit difficult to glue down so Green Glue is perfect to ensure the edges stay in place.

Of course, if you have regular caulk you can use it but as with the plywood and fiberboard, it’s not the best choice.

If Green Glue is too expensive and you want something quite as effective at a lower price, you can check out this green glue alternative article.

  • Adds up to 9 STC points
  • Stays pliable
  • Mold and mildew resistant

Green Glue Noiseproofing Compound is the best acoustic caulk on the market.

It is the highest-rated sound dampening compound out there that can add up to 9 STC points when used between two layers of drywall or plywood.

It is used to fill cracks, gaps, seams 1/8” to 1/4″ and can even be used as a glue to further soundproof your area.

Green Glue remains pliable and will not dry out, harden or crack.

It can be used just about anywhere since it is mold and mildew resistant as well as non-toxic and carries a low odor.

Application is easy and cleaning up any spills is simple, just soap and water before the glue cures.

green glue on fiberboard of the soundproof generator box

6. Applying the second layer of soundproof insulation. 

If you did use Green Glue to glue your MLV to the fiberboards, then technically this would be your third layer of soundproofing insulation

As previously stated, layers matter when soundproofing.

In this step, we will use some foam mats to further silence your soundproof generator box.

Foam mats have a soft surface so they do not allow sounds to bounce off their surfaces.

When placed against the MLV they act as a surface to absorb and quieten sounds rather than leaving hard surfaces for sound to bounce off and reverb and echo.

Just like the MLV, measure and then cut the foam mats to size.

You can use the Green Glue Compound to attach the foam mats to the MLV on the fiberboards.

Use Green Glue to also secure the edges of the foam mats.

You may also use any of the following foam panels in this best acoustic foam panels review guide.

  • Noise-reducing design
  • High-density foam with no toxic phthalates
  • Water-resistant

The ProsourceFit extra thick mat is made from high-density foam that contains no toxic phthalate.

It is an impact absorbing as well as a sound-absorbing surface for the reduction of sounds.

With its noise-reducing design, this interlocking foam mat can greatly reduce the transmission of sounds.

Lay this up against the MLV and fiberboards of your generator box and be amazed by how much they all dampen the sounds coming from your generator.

The pieces are lightweight and are very easy to cut by using your utility knife.

This foam mat includes 6 pieces with each tile measuring 24” x 24” x 3/4”-thick.

7. Time to assemble your generator quiet box

Now it is time to assemble your generator silencer box.

One by one, attach the 4 pieces of fiberboard with its soundproofing layers(the walls) to each other using screws or nails.

It is advisable to use screws instead of nails in case you want to modify your box in the future.  

It’s harder to remove nails than screws but if you’re sure you won’t be modifying your box, go ahead and use some nails.

After making sure the walls are all attached, it’s time to attach the top of the box and secure it with screws or nails.

If you wish, you can opt to use some hinges for the top so that you can have easy access to your generator for maintenance.

If you do choose to use hinges, the vents will have to be installed differently since the hose will be in the way and become an obstruction.

However, it is a small adjustment, and doing so will give you access to the generator instead of unscrewing the top of the box.

8. Installing the ventilation ducts

Your generator box needs adequate ventilation to function as it should and to also reduce the chances of it overheating.

To avoid a total disaster, add some vents to your generator noise reduction box to ensure there is a supply of air as well as the flow.

This is why we made those two holes earlier.

These holes are where you are going to place your vending ducts. 

Use venting ducts with lots of bends in them since sound waves travel in a linear path.

The type of venting ducts will lessen the number of sounds you hear from your generator due to the many bends and curves.

Place the hose into the holes you had cut out earlier and secure them in place.

You need them to stay in place and not jump around.

After that, place some vents over the ducts and that’s it.

You are now ready to enjoy some quiet time without the constant humming or buzzing of your generator. 

The ipower non-insulated flex air ducting vent hose is flexible for use in a wide variety of projects around the home even those hard to reach places.

It is made up of high-quality aluminum for strength and durability.

With a fireproof coating that allows it to endure temperatures up to 185°F, feel safe to use just about anywhere.

The vent hose is easy to cut to size and comes with 2 pairs of 4-inch stainless steel clamps to secure it.

This venting duct hose measures 4 inches (diameter) x 8 feet (length) when fully extended.

Reduce generator noise without building a generator box

We’ve decided to include this section for those who do not have the time or confidence to build a generator quiet box.

If that is the case then you can do any of the following steps below:

1. Buy a quiet generator

If you have the budget and can afford it, then you should buy a quiet generator.

Do note that the bigger your generator is the louder it will be.

You can opt for an inverter generator since they are the quietest due to the technology that is integrated during manufacturing.

2. Adding a muffler to your generator

This isn’t something I recommend you do on your own.

Consult with an expert before attempting to do this or better yet have them do it for you.

Car mufflers work in the same here as they do to muffle noise in cars.

3. Water absorption

Water absorption is an old school trick to reduce generator noise.

You need a bucket of water and a galvanized flex tube hose material.

Attach one end of the hose to the exhaust and the other end should be placed into the bucket of water.

This way the sound travels through the hose and goes into the bucket of water that absorbs most of the sounds.

Remember to keep the water as far away as possible from the generator and make a small hole on the hose at its highest point to prevent water from sucking back into the generator.

4. Rubber absorption 

Something as simple as moving your generator from a concrete surface to a rubberized surface like a rubberized mat can minimize sounds. 

If your generator is on a hard surface try placing it on a soft surface and listen if you can hear a difference.

5. Redirect Exhaust Pipe

Check to see whether your exhaust pipe is laying horizontally or vertically.

Moving the exhaust pipe from a horizontal to a vertical position can redirect and reduce sounds coming from your generator.

6. Soundproof your room.

If all else fails, you will have to start looking for ways to soundproof your home.

For ways on how to soundproof a room, click the link to read more.

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