Is Styrofoam a Good Insulator?

No matter what we do or where we go, having good insulation is one of the most important things in our lives, and most of the time we aren’t even aware of it.

It will always be crucial to keep our homes warm in winter and cool in summer, then our offices and other public areas and of course ourselves.

As we all know, the more layers we have warmer we will feel and the reason behind this is pure physics – the air is a bad conductor of heat. 

By wearing many layers more air is trapped within them and since air cannot conduct warmth it automatically stays around us.

This is exactly why Styrofoam presents amazing insulation - it is composed mostly of air which makes up around 98% of it, creating a perfect barrier between the object that it insulates and the surrounding area.

Is Styrofoam a Good Insulator?

How Does Insulation Work?

Let us first cover some basics to understand better how Styrofoam works. 

There are three mechanisms through which warmth is spread and they are called conduction, convection, and radiation. 

The easiest way to explain these three is to imagine a pot with water that is being boiled on a stove.

Conduction happens when warmth moves through a material, for example when warmth moves from the bottom of the pot to the handle that gets heated and warmth is then transferred with direct contact.

Convection happens when the warmth gets distributed through liquids and gases, for example, through water that is about to start boiling and this happens thanks to movements of millions of molecules.


Radiation is the third mechanism though which warm is transmitted in the form of rays or waves. For example, though radiation warmth is transferred from the flame to the pot.

How Does Styrofoam Work?

Styrofoam is the trademarked term created by the company The Dow Chemical Company in 1941 and it is used for polystyrene foam, which is plastic primarily made of petroleum.

Styrofoam can be found in two versions: expanded and extruded; and one of the main differences is that the extruded version is water-resistant, while the intruded one isn't.

Another one is that the extruded type is a better insulator thanks to its higher R-value than the value of the intruded one.

Now, you might be wondering what the R-value is. The easiest way to explain it is to use a definition by Wikipedia:

“In the context of building and construction, the R-value is a measure of how well a two-dimensional barrier, such as a layer of insulation, a window or a complete wall or ceiling, resists the conductive flow of heat.”

This means that if you wish to have amazing insulation it is supposed to have a higher R-value and the higher this value is, the lower the amount of heat that goes into/out of your home will be.

Also, it is important to know that you can double the effect of Styrofoam by adding layers on top of each other and that way their R-values get added and two times less warmth is emitted or received.

For example, extruded Styrofoam has an R-5/inch value and the expanded R-4/inch. This is a much higher value than you would get from loose-fill insulation, such as mineral wool.

So, Is Styrofoam a Good Insulator?

This material is amazing for many reasons:

  • it is quite lightweight and very easy to transport
  • it absorbs shock phenomenally and is thus used for packaging in numerous industries
  • it is used as an insulator of course and also for creating various materials and disposable packages

This is because of its amazing trait and it is that Styrofoam turns to liquid at a certain temperature and can be shaped easily.

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It usually comes in white color and is composed of millions of tiny bubbles filled with air which enable it to work as a great insulator. The air has a very small mass and it is not enough to keep much heat.

Because heat is trapped in the air inside of these bubbles also means that conduction and convection cannot happen properly.

So there is some science and the reason behind the great success of the Styrofoam.

So the answer to the main question is – YES, Styrofoam is an amazing insulator.

Where is Styrofoam Insulation Used?

When we are talking about home insulation Styrofoam can be used pretty much anywhere – on roofs and floors, walls, in basements, attics, on ceilings, as exterior insulation and also for acoustic insulation.

Not only that it is used for insulation in homes and public buildings but also is widely used appliances, such as refrigerators, freezers and other industrial cold storages.

styrofoam insulation

Another reason why it is so widespread is the fact that it is water-resistant and quite durable – once you install it you can rest assured that you'll have quality insulation for years to come.

In case you wish to use environmental-friendly materials, I have some good news, Styrofoam is again your choice since it is just that and also recyclable.

Perks of Using Styrofoam for Insulation

As already mentioned Styrofoam is your go-to material if you wish to insulate any space and the reasons why you should choose it are numerous:

  • Quite affordable: for example the price for 4 blocks of dimensions 1/2 in. x 1 ft. x 1 ft. can be found for around $20 on Amazon
  • Recyclable and environmental-friendly
  • Lightweight and easy to carry
  • Good quality insulator
  • Water and moisture resistant
  • Mechanical resistance – it is perfect for applications which bear a lot of loads (i.e. floors)
  • Durable – it has a life span of around 50 years and maintains its low conductivity

Styrofoam Alternatives

In case you are looking for any other insulation options here are some good alternatives you could think about.


This is one of the best “green” alternatives in case if you are looking for a material that is biodegradable and also renewable.

Its main element is created from mushrooms that are grown into shapes that are fit for insulation and this happens thanks to a certain mixture of agricultural bio-waste.


Cellulose is also one of the best eco-friendly materials you could you for insulation, even though it is not used that commonly.

Its main ingredients are cardboard, paper, and several other materials. Just like Styrofoam, it is also quite lightweight and easy to carry.


Now, if you are looking for a “safe” choice and don’t wish to experiment much, then fiberglass could be your option, especially if you are about to install it on unfinished walls.

This is the best option if your home, work area or any other space is still under construction. You could do this yourself, or hire a company that will install it for you.

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Final Word: On Insulating with Styrofoam

Based on everything written above, I think it is safe to conclude once more the Styrofoam is a very good insulator and that you will be satisfied with it no matter where you install it (as longs as its fit for that purpose).

I hope that all of this information on Styrofoam will be of help to you and that some of them will give you a fuller picture of its benefits and places where you could use it.

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