Two of the most popular types of insulation are spray-on and fiberglass. However, did you know that there’s a product that gives you the best of both worlds? And, no, we’re not talking about blown-in fiberglass insulation.

Spider insulation, while similar to traditional blown-in fiberglass insulations, is a spray-on fiberglass insulation material. Ultimately, you can apply spider insulation to any surface that requires insulating, from walls to ceilings and floors.

What makes spider insulation different from traditional blown-in fiberglass insulation? How and where can you use spider insulation to its fullest extent? What exactly is spider insulation?

Become an expert in spider insulation and learn the best places to apply spider insulation in your home!

What’s a Spider Insulation?

Ultimately, spider insulation is a blown-in fiberglass insulation. 

However, its interlocking fiber technology helps build a support structure that allows this insulating material to behave more similarly to spray-on insulation in certain cases.

By utilizing interlocking fibers in a web-like pattern (hence the name, ‘spider insulation’), spider insulation does not require any netting or adhesives to remain in place in any small space.

Additionally, these interlocking fibers meant that spider insulation does not feature formaldehyde as a bonding agent, unlike other types of blown-in fiberglass insulation. 

Its manufacturer, Johns Manville, regularly declares it ‘Formaldehyde-free’ in its advertising.

Spider insulation is slightly more expensive than competitors, ranging between $1.50 and $1.65 per square foot. However, this cost accounts for the inherent safety and quality of the product.

Spider insulation, just like spray foam, does not settle, and as such, you are unlikely to face any insulation issues that do not stem from structural or drainage issues in the home itself.

Advantages of Spider Insulation

1. Formaldehyde-Free

Spider insulation does not feature any formaldehyde in its composition, reducing health issues that come from the carcinogen. Many other forms of insulation, including traditional fiberglass insulation, utilize formaldehyde as a binding agent.

2. Spider Insulation Is Non-Corrosive

Sometimes, certain forms of insulation (such as polyurethane foams) can corrode through your valuable home supplies, such as pipes, wiring, and studs when exposed to water.

Thankfully, spider insulation is entirely non-corrosive.

3. Sound-Reducing

The density of spider insulation makes it highly conducive to blocking the travel of sound, making it an excellent soundproofing measure on top of an effective insulator.

4. Mold-Inhibiting

When wet, fiberglass insulation can become a hotbed for mold and mildew growth. However, spider insulation features a built-in mold inhibitor that can prevent or mitigate mold growth where necessary.

5. Low-Waste

Spider insulation is not a set-it-and-leave product. Installers will add excessive amounts of spider insulation to a job, scrape off any excess, and utilize a set of specialized tools to reclaim excess insulation for use in another job.

Disadvantages of Spider Insulation 

1. Cost

While spider insulation is not break-the-bank expensive, it is more costly than other competitors. Ranging between $1.50 and $1.65 per square foot, spider insulation can cost more than spray foam insulation, though it is far safer to handle than most other insulating materials.

2. Still A Fiberglass Insulation

While spider insulation is an advanced form of fiberglass insulation, it still suffers from some of the shortcomings of traditional blown in fiberglass. For example, spider insulation loses its R-Value at lower temperatures due to the air exchange rate.

How Is Spider Insulation Installed? 

Ultimately, spider insulation faces a very similar installation process to traditional blown in fiberglass insulation. A team of professional insulation installers will show up at the job site, blow insulation into any necessary locations, and vacuum up any excess material.

However, a few matters differ during installation. As spider insulation does not require any adhesive or netting when installed, installers can easily blow in excess material, creating a lumpy and uneven appearance.

Installers will use specialized tools such as scrapers to remove excess material and make it flush with the walls, providing an even and pleasant appearance.

When installers vacuum up any fallen or excess material, they can use it in another installation project as a cost-saving measure.

When you have an installer handle your spider insulation, you can expect to pay around $400 to $1,800 for their fees.

Where Is Spider Insulation Used?

As a form of blown-in fiberglass insulation, you can use spider insulation in many of the same scenarios where you would use other fiberglass insulators.

Traditionally, homeowners will choose to install blown-in insulation in their attics. In an attic environment, spider insulation is an excellent solution for all surfaces from walls to floors, inclined walls, and ceilings.

Blown-in insulation is also an effective treatment for a home’s walls, with an easier installation process due to a lack of required netting or adhesives.

Ultimately, you can use spider insulation in just about any scenario where blown-in insulation is applicable and then some.

Alternatives to Spider Insulation

1. Blown Cellulose

While blown cellulose does not insulate as well as fiberglass, it is more environmentally friendly, safer to install (though a respirator is still required), healthy, and cheaper. However, its lifespan is also shorter as it is made of organic materials such as paper.

2. Mineral Wool

Another natural material insulator, mineral wool is cheap and somewhat effective. However, unlike spider insulation, mineral wool may contain traces of formaldehyde.

3. Recycled Cotton

Denim is an effective material for more than just your jeans. A recycled cotton insulating layer is best for soundproofing, but can also provide up to an R-13 of thermal insulation. However, it may not have the same mold-proof or interlocking features as spider insulation.


Evan has decades of experience as a project manager for large-scale commercial renovation home-building projects throughout the US. Currently, Evan runs a successful construction management company in Virginia.

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