How To Soundproof A Utility Closet With A HVAC System

Being able to tuck away something like a HVAC system in a utility closet is something of a blessing, as very few people want to be able to see the inner workings of their AC unit.

However, a common issue is that these systems can make a lot of noise when in use, and utility closets can often be hidden in annoying places, such as living spaces or bathrooms.

The last thing anyone wants when trying to relax at home is to listen to the HVAC system grumbling away in the utility closet. Sure, you’ll probably get used to it after a while, but why not doing something about it instead?

Soundproofing a utility closet is a wise investment for the future, and will save you having to deal with irritating noises. In this article, I offer some top tips I have learned on how to soundproof a utility closet.

How Do You Soundproof A Space?

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When it comes to soundproofing anything, you have to rely on 4 main principles. These are:

  • Mass
  • Decoupling
  • Absorption
  • Damping.

Sound waves travel through solid surfaces (walls) through vibration, and can obviously travel easily through air. Therefore, to soundproof something, you need to restrict the amount of sound waves that can leave or enter a space.

Soundproofing can be done on a budget with easily obtainable items that you can buy either in home improvement stores, or online. Read my post on inexpensive ways to soundproof a room.

However, the more in-depth you plan on being with your project, the more money it’ll cost.

As mentioned earlier, I am going to suggest some of the best ways to soundproof a utility closet. You can pick and choose between which you would like to use.

It’ll probably be worth working out a budget before starting, just so you know what you should be sticking to.

How To Soundproof A Utility Closet

A utility closet can be made soundproof by the following methods:-

  1. Adding mass to the existing space
  2. Decoupling the walls
  3. Soundproofing the door – sealing the gaps and adding mass
  4. Sealing gaps and cracks in the utility closet
  5. Using Vibration Mounts for the HVAC
How To Soundproof A Utility Closet

Add Mass

The best place to start, providing you have the room, is simply to add mass to the existing space. The easiest way to do this is to add more layers of drywall within the utility closet.

Drywall is actually surprisingly useful when it comes to soundproofing because its structure makes it good at absorbing and damping sound waves.

When it comes to soundproofing a utility closet, you have the choice of either adding the drywall onto the existing walls inside the closet, or building a drywall box around the HVAC unit.

If you choose to do the latter, make sure you follow any manufacturer’s guidelines when it comes to ventilation for the unit, and make sure that the unit will still be accessible for when it needs to be serviced.

If you decide to add the drywall onto the existing walls, consider filling the space between the two with insulation foam.

On its own foam isn’t a good soundproofing material, but the point of this exercise is to add mass to the space, so in this circumstance it becomes quite a useful addition.

Make sure you’re thorough with your installation, as you don’t want to put in all of this effort for nothing.

Decoupling Drywall

This suggestion goes with the one of adding more mass, but is only really useful if you’re not limited by space.

Decoupling drywall involves splitting an existing piece of drywall into its separate layers, and then filling the space between them with insulation. This adds mass to the structure, which in turn limits the amount of sound that can pass through the wall.

To make the job even more effective, it’s worth trying to hand the drywall on decoupling mounts. These add another element for the sound waves to pass through, and should reduce the level of vibration that can pass through the structure.

You can also use alternating studs or a staggered stud wall for mounting the drywall, and all this means is hanging the two pieces of drywall off separate wooden studs. This means the two pieces theoretically hang independently from each other, thereby minimizing the amount of vibrations that can pass through the wall.

Obviously the staggered stud method will involve a bit of DIY knowledge, and is only really possible if you’ve got quite a bit of extra space in your utility closet.

If you decide to try decoupling drywall, make sure you use Green Glue too. This is a type of glue that turns sound waves (vibrations) into heat energy. It’s a great product and does make a surprising difference when soundproofing your utility closet.

Read my article on Green Glue which will give you a clear sense of how well it works for soundproofing.

Soundproof The Door

Soundproofing follows many of the same principles as weather insulation, one of the key points being that your efforts are only as good as the weakest point.

When it comes to soundproofing, the weakest point is usually the door (or window, but you probably don’t have many of these in a utility closet).

So when it comes to soundproofing a utility closet, it’s worth devoting much of your attention to the door.

The first thing to do is to install a weather seal along the bottom of the door. Obviously these are designed to stop drafts, but as mentioned above, soundproofing follows many of the same principles.

You can buy weather seals in various forms, and the right one will depend on the size of the gap below the door. However big this gap is, your intention is to close it.

The best sort of door seal is one made of heavy rubber. This is a great insulator, and will certainly help minimize the amount of leakage under the door. If you do decide to fit one, avoid the brush-style door sweeps, as these will essentially do nothing when it comes to soundproofing.

It’s also worth buying some acoustic sealant tape (check it out on Amazon) to fill the rest of the gaps around the door. This product is inexpensive and really easy to buy online, and simply fills the gaps with a material that will absorb sound waves trying to escape around the door.

Considering you’re limited by what you can actually do to a door, so it’s worth trying as many as possible.

Add Mass To The Door

Again, there’s probably not much you can do to add mass to the door. If you’re serious about soundproofing your utility closet, and you have a reasonable budget to work with, consider simply buying a new door.

Many standard interior doors are hollow-core, meaning sound can travel through them quite easily.

Consider replacing the standard door with one designed for exterior spaces. These will always be heavier, and are usually solid, and so will do a much better job at absorbing sound.

MDF (Medium Density Fiberboard) is a reasonably inexpensive material, and has much better absorption qualities than normal interior doors. These are easy to pick up in hardware stores, and are easy to install.

I also suggest you read my post on the best ways to soundproof a door.

Fill Any Gaps Possible

Sound can escape through gaps of any size, so if you’re serious about your soundproofing project, make sure you go around filling all gaps possible. This includes gaps between pieces of drywall, any cracks in the wall, and holes in which mounts are installed.

Identify all the gaps you can in the room and fill them with acoustic sealant. Unlike standard sealant, acoustic sealant remains springy, and so is less prone to cracking. It also has better sound absorbing qualities than normal sealant.

It’ll be particularly important to fill any gaps around the HVAC mounts, as these are a common source of vibrations passing into the walls.

Use Vibration Mounts

Depending on how your HVAC unit is installed in the utility closet, and assuming this is the thing that needs soundproofing, it’ll be worth using vibration mounts.

Vibration mounts are essentially rubber feet, or mounts, on which to set the HVAC unit. These will help to reduce the vibration that can pass from the unit into the walls.

Installing these will possibly be one of the harder jobs on this list as it could mean having to take the HVAC unit down so it can be put up again with new mounts.

If this is something you’re able to do then it will make a difference, but only go ahead with it if you’re confident enough in your technical ability.

Final Thoughts On How To Soundproof A Utility Closet

Hopefully this article has given you some information on how to soundproof a utility closet.

The most important thing to remember is that adding mass is the most effective way of soundproofing any space, but you need to make sure that any work done in the utility closet won’t impact its functionality. This is particularly true when it comes to HVAC units, as you don’t want cause a fire risk by reducing ventilation.

The other thing to remember is to reduce vibrations that come from the HVAC unit. This is easily done by sitting the unit on foam pads, or by installing it on vibration mounts.

The more you can reduce vibrations at the source, the easier it’ll be to soundproof the room.

Whatever methods you decide to use, bear in mind that the more effective you want it to be, the more money you’ll have to spend.

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