Is Insulation Heavy? (Different Types and Quick Facts)


It is sufficiently established that your home insulation affects your energy spending and air quality in your home. More interestingly, the thickness of your home insulation determines how well it works. Therefore, you must have thought about how heavy your insulation needs to be to achieve the desired impact.

Different insulation types come with varying weights or thicknesses. Fiberglass weighs about 1lb per cubic foot. Cellulose insulation is denser than fiberglass and could weigh as much as 3lbs per cubic foot. Spray polyurethane foam’s weight varies depending on if it is open-cell or closed-cell. Open cell foam insulation weighs around 0.5lbs while its closed counterpart weighs around 2lbs.

There is a lot to know to get your home insulation right. How thick should your home insulation be? How heavy is the ideal insulation for your home? Also, are there any consequences to squishing your insulation material?

These are some of the exciting questions we authoritatively answer in this guide.

Is Fiberglass Insulation Heavy? 

Fiberglass is reputed as one of the lightest insulation types you can get for your home. Such lightweight nature translates into a broader range of installation methods.

Generally, fiberglass insulation weighs 1 lb per cubic foot. For context, you will need more than 20 inches of blown-in fiberglass to hit an R-factor of 49.

We will be diving deeper into the concepts of R-values later on in this guide.

Is Spray Foam Insulation Heavy? 

The weight of your spray foam insulation depends mainly on the type you go with. While some spray foam can weigh as little as 2/5lbs per cubic foot, others can weigh up to 4lbs per cubic foot upon full curing.

As a homeowner, installers would commonly recommend either open-cell spray foam insulation or the closed-cell variant.

As you can infer from the name, the open-cell foam has an open structure, allowing for air penetration. They are a bit lighter and can weigh around 0.5lbs.

Being significantly airier, its texture resembles a sponge, having a notably cushioning feel.

The closed-cell foam is way thicker. It is packed and hard. Here, there are no spaces between the cells, ensuring higher density.

A closed cell spray foam insulation can weigh as much as 4 lbs per cubic foot.

While open-cell spray foam excels more at shutting off noise, closed-cell spray foam insulation has advanced capabilities in preventing mold and saving energy.

Is Cellulose Insulation Too Heavy?

Cellulose insulation is one of the oldest insulation types deployed in homes, made predominantly from recycled denim or paper.

Compared to fiberglass, cellulose insulation is heavier.

Cellulose insulation can weigh up to 3lbs per cubic foot. When compared in R-value, 3.5 per inch of cellulose insulation beats equivalent fiberglass batts by over 22%.

What is the Heaviest Insulation?

Home insulation is traditionally rated in R-values, which infer how thick such insulation is. This is a measure of an insulation’s performance, regarding how well it can manage the inflow and exit of air in your home.

Insulation materials with higher R-values (meaning they are heavier) generally suggest superior energy efficiency and weather management. Inevitably, insulation materials with such premium R-values cost way more.

The insulation material with the highest R-value – and consequently the highest thickness – is vacuum insulated panel. This is seconded by aerogel.

Specifically, the vacuum-insulated panel has a 2.54cm thickness and RSI-value running as high as 8.8m2·K/W.

Silica aerogel follows closely at a 0.54cm thickness and 1.76 8m2·K/W RSI-value.

Should Insulators Be Thick?

Most insulation installers agree that higher thickness ratings deliver more excellent home heat management.

Often, the thicker the insulation, the higher its capacity to modulate the flow of heat from outside into your home during summer. Similarly, thicker insulations perform better in regulating air flow from inside your home outdoors during winter.

When an insulation’s thickness is doubled, there tends to be a corresponding 200% increase in the R-value of such insulation. The practical implication is heat loss being slashed by 50%, with energy savings accordingly doubled.

That said, various sections of your home have maximum insulation thicknesses you are advised not to exceed.

For example, if you install insulation in your attic, you shouldn’t use insulation thicker than 14 inches. This corresponds to a maximum R-38 value.

How Thick is the Insulation?

Digging deeper, the thickness (or overall dimensions) to which you should cut your insulation depends on the material, the area, and the intended purpose for deployment.

For example, let us assume you are deploying fiberglass insulation in your home. To achieve an optimal 30 R-value, you should be gunning for between 10-12 inches of fiberglass.

Furthermore, let u say you are explicitly deploying your fiberglass insulation in your walls. Walls don’t have enough space, necessitating compressing your insulation.

You would need around 5 inches of your fiberglass insulation to hit an average R-value of 14. Should you be using cellulose insulation, you may not need something as thick as that.

What If You Were Installing the Fiberglass Insulation in Your Attic?

Attics need a significant insulation supply to make tangible savings on your utility bills. Therefore, to get a good R-value, you should use a minimum of 12 inches of fiberglass insulation.

Can You Squish Insulation?

Most insulation types lack flexibility. This is more particular with fiberglass insulation, where manufacturers produce batts to meet standardized metal framing and wood dimensions.

This robs you of versatility, meaning you would have to manipulate the insulation for your specific application.

Such lack of flexibility is commonly compensated for by compressing the fiberglass insulation to your unique dimensional preferences.

Compressing insulation types like fiberglass below the thickness recommendations of the manufacturer may not necessarily affect installation.

However, compressing such fiberglass batts lower the thickness denoted in the label could deteriorate the fiberglass’s R-value.

This explains why it is advised to consult the specifications provided by the insulation manufacturer before squishing your insulation.

Most manufacturers stipulate the drops in the R-value you can expect if you squish your insulation. If you don’t have such data, feel free to reach out to the manufacturers to supply such.

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