Acoustic Insulation: Ultimate Guide

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Having the right insulation is key to your home. Obviously there’s the thermal efficiency to think about, but soundproofing your home with the perfect acoustic insulation is worth considering too. Whether it’s your loft, your external walls, or under your floor , choosing soundproof insulation can make a real difference to how comfortable your home is to live in.

But knowing which insulation types are the most soundproof can be tricky. That’s why we’ve put together a helpful guide about the best soundproof/acoustic insulation to help. Below we’ll cover the key benefits of finding soundproof insulation and then provide you with some advice about the very best options out there for you.

What Is Acoustic Insulation?

Soundproof insulation, or acoustic insulation as it’s sometimes known, is so called because it’s insulation that’s soundproof. And that works in one of two ways:

  1. Absorbs sound in a room
  2. Blocks sound transmission between rooms


The best soundproof/acoustic insulation on the market will offer both of these features, but some may only offer one – but offer it really well – so they’re still worth considering, especially if you only require soundproof insulation for a specific room or purpose. 

It’s important to note that soundproof is a bit misleading here. Your room will not be fully soundproof in the traditional sense by using this type of insulation. That is to say, you will still hear noises, but they will be greatly reduced. 

And the better the STC value of the insulation, the better that sound reduction will be.

STC Value Explained

If you’ve been looking into insulation for a while then the chances are you’ll have heard of an R-value. If you haven’t, the R-value just tells you how thermally efficient the insulation is – the higher the value the higher it resists the transfer of heat, meaning your home stays warmer or cooler for longer, depending on what you want.

Well, the STC value (Sound Transmission Class) is similar, but instead of focussing on thermal efficiency, it focuses on how well the insulation does when blocking sound. The higher the value, the more sound it’s capable of blocking and the more comfortable and quiet your home will be. 

There are other measures such as NRC (Noise Reduction Coefficient) but these are often overly complicated and in most cases, if the STC value is high, so is the NRC value anyway. So for the purpose of today’s guide, we’ll focus only on the STC value.

Benefits Of Installing Acoustic Insulation

Before we move on to the best types of insulation for soundproofing, let’s look at the benefits of installing soundproof insulation, and no, not all of them relate to the fact that it’s soundproof:

Comfort In Your Home

With any kind of insulation your home becomes more comfortable because your home is better able to keep stable temperatures. But with soundproof insulation, not only are temperatures more comfortable in your home, but noise levels are too. 

Thermal Efficiency

All insulation will bring some element of thermal efficiency to your home, even if acoustics are their main concern. So soundproof insulation will mean your home stays warmer for longer during winter months, and cooler for longer during the summer. 

Energy Bill Savings

You’ll make significant energy bill savings each year when you install any type of insulation in your home, including acoustic insulation. Because your home will hold on to heat for longer, you won’t spend as much money heating it. 

Green Solution

The less heating you use the less carbon emissions your home will produce and the smaller your carbon footprint will be. Switching to soundproof insulation does more than just make your home a better place, it makes the world a better place, too.

Peace & Quiet

And, of course, we have to mention the whole point behind acoustic insulation: You’ll enjoy far more peace and quiet in your home as a result – both in terms of noise outside your home getting in, and noise inside your home transferring between rooms. 

Things To Consider Before Purchasing Soundproof/Acoustic Insulation

Before purchasing acoustic insulation it’s best to think about a few key things to ensure you get the right insulation for your needs – and it comes down to 3 main things:

  • What you’re hearing
  • The cost of the insulation
  • The installation method


These things will affect the insulation you’ll ultimately choose for your home.

What Sounds Are You Hearing?

There are two categories of sound that can be stopped or seriously reduced by acoustic insulation and both cover different types of sounds you might hear in your home or apartment building:

Airborne Sounds

Airborne sounds describe sounds that move through the air and reach you in your home or apartment. The sorts of sounds that may be categorised as airborne sounds are sounds you’ll hear like:

  • Conversations
  • Traffic noise 
  • Plane noise
  • TV’s
  • Radios 

If noise is travelling from outside to inside, between rooms, or between floors in a building, then it’s probably airborne sounds you’re dealing with. 

Impact Sounds

Impact sounds are those sounds you hear when something is being struck. Things like someone putting up a picture on the wall, dropping something on the floor, or vacuuming upstairs and hitting the skirting boards.

When something is struck, it will inevitably make a noise. But if that noise is particularly loud, you could benefit from soundproof insulation to help reduce it to a more manageable level for your home.

Knowing which sounds you’re hearing regularly is crucial in making sure you pick the right acoustic insulation, as different insulation types are better at stopping different types of noise.



Cost is another big consideration. If the most effective type of soundproof insulation is outside your budget, then you obviously won’t opt for it. We’ll cover some average prices of the different types of acoustic insulation below, but it’s important to note that these may differ between insulation installers

When you compare insulation installers with us, we’ll always try to find you the best deals from local insulation installers to you. But their prices may differ from the examples we provide later in the post. 


The final thing you’ll want to consider is the way the insulation is installed. Some are far more complex than others and can impact you and your household for a lot longer. For some, the installation method won’t matter so much so long as they get the insulation they want at the end of it. 

Still, it’s worth considering how insulation in batts, rolls, spray, and foam might impact your home during the installation process, and it’s worth thinking about how long that installation may take to ensure you can accommodate it.

The Best Soundproof/Acoustic Insulation Types

Below we’ll cover the best soundproof/acoustic types in the industry so you know which ones you should be considering:

Blown-In Cellulose 

Blown-in cellulose is made up of recycled paper, wood, and plant based products that have been chemically treated to become more fire-resistant. It’s specifically designed to fill in gaps between walls, pipes, and joists that might otherwise be difficult to fill. 

  • STC Value: An average of 39.
  • How It Stops Sound: It works by both absorbing sounds in a room and blocking sounds from passing between gaps in walls, and between pipes and joists, thanks to its ability to fill in gaps that would otherwise be left for sound to travel through. 
  • Sounds It Can Stop: Because of its ability to absorb and block sound, blown-in cellulose insulation can handle both airborne and impact sounds.
  • Cost: On average it costs around £55 per square metre, with average job costs coming in at around £300-£500 depending on labour and location.
  • Installation Method: The material is ‘blown-in’ to the gap using a nozzle and a blower to install. It requires specialist equipment – hence the price. 

Mineral Wool 

Mineral wool, also sometimes known as rock wool, is made of natural slag – a waste product from the steel industry when firing iron or iron ore. It’s naturally fire resistant, and the material is spun into fibres to create insulation. 

  • STC Value: An average of 45.
  • How It Stops Sound: This type of insulation is outstanding at absorbing sound and blocking it. Its lightweight construction makes it incredibly effective at absorbing sound, and its natural stone slag makeup makes it great for blocking sound, too. 
  • Sounds It Can Stop: Both airborne and impact sounds are absorbed or blocked by mineral wool insulation. 
  • Cost: Because there are a range of installation methods – rolls, batts, boards, and blown-in – the prices vary significantly. But the overall cost is usually around £150 to £300 per day for labour, and around £20 per square metre for materials. If you opt for blown-in mineral wool, then the specialist equipment required will also increase the price.
  • Installation Method: There are many options for mineral wool – rolls, batts, rigid boards, or blown-in.



Fibreglass insulation is made of glass that’s heated to a liquid and then spun into insulation with plastics to make it more pliable. It, again, is capable of being installed in a variety of forms – meaning you can choose an installation method that suits you best.

  • STC Value: An average of 39.
  • How It Stops Sound: So long as there is a good thickness to the fibreglass insulation then it will be capable of both absorbing and blocking sounds. The important thing here is the thickness. The thinner the insulation, the more sound will travel through it. 
  • Sounds It Can Stop: Again, so long as the thickness is right, both airborne and impact sounds can be stopped here. 
  • Cost: Fibreglass insulation is excellent value for money, with some estimates suggesting that an entire detached house could be insulated for less than £900 when using this type of insulation. 
  • Installation Method: Can be installed in rolls, batts, or loose-fill.


Insulation Mats 

Insulation mats are typically made of rubber or vinyl, and are specifically designed to provide acoustic insulation in thin rolls that can be used as underfloor insulation to provide some degree of soundproofing. 

  • STC Value: An average of 40.
  • How It Stops Sound: This type of insulation is specifically designed to be used as underfloor soundproof insulation, so its main way of stopping sound is through absorbing it, rather than blocking it. 
  • Sounds It Can Stop: Mostly impact sounds are stopped here, meaning it won’t necessarily stop noise from conversations in other rooms etc. But it is incredibly adept at absorbing impact sounds, so footsteps won’t disturb your peace and quiet with this insulation type. 
  • Cost: Per square metre insulation mats can cost anywhere from £20-£50. Labour costs will come to around £150 per day for this type of insulation, but it may be more depending on the complexity of the installation.
  • Installation Method: These are insulation roll mats designed to be used underfloor, which means your floors may need to be lifted to install the mats – this could impact your decision on whether they’re appropriate for you.


Cotton Batts

Cotton insulation is usually provided in batts, and the cotton is usually taken from cellulose fibres from clothing and then bound into batts that can be installed quickly and easily between cavity walls

  • STC Value: An average of 51.
  • How It Stops Sound: Cotton is actually an excellent material for both absorbing and blocking sound thanks to its material makeup. When the cotton is then bound into batts, it only increases its ability to prevent sound transmission. 
  • Sounds It Can Stop: Both airborne and impact sounds can be dealt with effectively with cotton batt insulation. 
  • Cost: Cotton batts roughly run at about 20% more expensive than fibreglass insulation, meaning a detached house would cost around £1100 to insulate. 
  • Installation Method: Cotton batts are designed to be easily cut to size and placed in between walls, joists, and floors.


Spray Foam

Spray foam – available in both closed cell and open cell – have certain amounts of soundproofing abilities, but open cell spray foam generally performs better for sound absorption than closed cell foam does. 

  • STC Value: An average of 39. 
  • How It Stops Sound: Spray foam is great at absorbing sounds between rooms and between your home and the outside world. It won’t necessarily block it, but it can be installed in hard to reach places which is a huge benefit. 
  • Sounds It Can Stop: Both airborne and impact sounds can be muffled by spray foam insulation, but neither will be fully stopped. Have spray foam installed vs no insulation at all, and you’ll certainly notice a quieter home, but it won’t be as quiet as some of the other options on the list today. 
  • Cost: Spray foam in general will cost between £20 and £50 per square metre, but open cell spray foam tends to be at the lower end. On top of that, you can expect to pay around £350 in installation costs, too, but this will vary.
  • Installation Method: Spray foam requires specialist equipment to install because it is sprayed into the space. Because of this specialist equipment, spray foam is generally one of the more expensive options out there, with only average to good soundproofing. 

Check out our full guide for more information about soundproofing spray foam insulation.

Soundproof Insulation Ranked By STC Value

  1. Cotton batts – 51
  2. Mineral wool – 45
  3. Insulation mats – 40
  4. Fibreglass – 39
    Blown-in cellulose – 39
    Spray foam – 39

But a high STC value isn’t all you’ll need to think about. What about specific scenarios?

If you have time, read our full guide on the best soundproof insulation materials. 

Best Acoustic Insulation For…

Internal Walls 

Cotton batts are one of the best options when installing insulation in internal walls or cavity walls because of their ease of installation. Although it isn’t the cheapest option you can opt for, it is the one with the highest STC value and ability to both absorb and block airborne and impact sounds.

A couple of great alternatives include:

  • Mineral wool (for an excellent STC value alternative)
  • Fibreglass (for a cheaper alternative with still excellent soundproofing qualities)

External Walls 

For external walls there are a few options open to you, but mineral wool seems to be the more popular and efficient choice. The STC value is excellent and it’s naturally fire resistant, too, providing you with some additional protection, all whilst being great acoustic insulation. 

You might also consider:

  • Fibreglass (as a cheaper alternative with similar additional protective properties)


Blown-in cellulose insulation is perfect for lofts because of the way it can get between joists and pipework effectively. The STC value is good, meaning noise will be absorbed well enough in a space that doesn’t necessarily need to be soundproofed as effectively as others. 

If you’re looking to soundproof your loft because it’s more of a usable space then think about:

  • Mineral wool (for better STC values)
  • Fibreglass (for a similar STC but additional protective properties such as natural fire resistance)


For underfloor insulation, insulation mats are an excellent option. They can be installed underfloor with ease and are excellent at reducing impact noise – your biggest concern on floors by far. The STC value is good enough to provide soundproofing benefits. 

Some other excellent alternatives include:

  • Mineral wool (for all round soundproofing – specifically in batts or rolls for underfloor insulation)

How Insulation Advisor Can Help

Now that you have an idea about the best soundproof/acoustic insulation on the market, you can start to think about which might be most suitable for your home. And then, when you’re ready to look for an insulation installer near you, we’re on hand to help.

Compare local insulation installers with Insulation Advisor today for the best deals and quickest comparisons.

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