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Fiberglass Insulation vs. Spray Foam Insulation: What's the Difference?

Edited by Aimie Carlson || By Janet White || Published on January 1, 2024
Fiberglass insulation uses fine glass fibers for thermal insulation; spray foam insulation is a chemical mixture that expands into a foam for sealing and insulating.

Key Differences

Fiberglass insulation is made from fine strands of glass woven together, providing thermal and sound insulation. Spray foam insulation, on the other hand, is created from a chemical reaction that produces a foam, expanding to fill spaces and forming an air-sealing barrier.
The installation of fiberglass insulation typically involves fitting batts or rolls into spaces between studs or joists, while spray foam insulation is applied by spraying a liquid that expands into a foam, conforming to the shape of the space it fills.
Fiberglass insulation has a lower R-value per inch compared to spray foam insulation, meaning it is less effective per unit thickness. Spray foam insulation provides a higher R-value, making it more efficient in preventing heat transfer.
Generally, fiberglass insulation is more cost-effective and easier to install, making it a popular choice for budget-conscious projects. Spray foam insulation is more expensive but offers better air sealing and moisture resistance, which can lead to long-term energy savings.
Fiberglass insulation is versatile and can be used in various parts of a building. Spray foam insulation is particularly effective for sealing gaps, cracks, and hard-to-reach areas, providing excellent air sealing properties.

Comparison Chart


Made from fine glass fibers
Composed of a chemical mixture that expands into foam


Involves fitting batts or rolls
Applied by spraying, expands to fill spaces

Insulating Ability

Lower R-value per inch
Higher R-value, more efficient


More affordable, budget-friendly
More expensive, but offers long-term savings

Use Cases

Versatile, suitable for various building parts
Ideal for sealing gaps and hard-to-reach areas


Subject to settling over time, less durable
More durable, maintains shape and effectiveness over time

Environmental Impact

Can be itchy and requires protective gear during installation, often contains recycled materials
Produces off-gassing during application, but provides better energy efficiency overall

Fiberglass Insulation and Spray Foam Insulation Definitions

Fiberglass Insulation

Fiberglass insulation refers to a lightweight, yet effective, insulating material made from glass.
Fiberglass insulation was chosen for the office building due to its lightweight nature.

Spray Foam Insulation

An insulation method involving the application of a rapidly expanding foam, sealing air leaks effectively.
To improve the home's air sealing, spray foam insulation was used around windows and doors.

Fiberglass Insulation

A type of insulation featuring a fibrous texture, primarily used for heat and acoustic insulation.
The new construction project used fiberglass insulation for its sound-dampening properties.

Spray Foam Insulation

An insulating material that expands and hardens into a foam, providing an air-tight seal.
The contractor recommended spray foam insulation for the basement to prevent moisture intrusion.

Fiberglass Insulation

An insulating material made from woven glass fibers, offering cost-effective thermal resistance.
Fiberglass insulation is commonly used in residential homes for its affordability.

Spray Foam Insulation

A foam created on-site from a liquid mixture, offering superior insulating properties.
They used spray foam insulation in the renovation project for its superior energy efficiency.

Fiberglass Insulation

A thermal insulation material consisting of extremely fine fibers of glass.
They installed fiberglass insulation in the walls to improve the home's thermal efficiency.

Spray Foam Insulation

A chemical-based foam used for insulating buildings and sealing gaps against air and moisture.
Spray foam insulation was applied to the attic to prevent heat loss.

Fiberglass Insulation

A material composed of fine glass fibers used for thermal and sound insulation.
The attic was insulated with fiberglass insulation to enhance energy efficiency.

Spray Foam Insulation

Spray foam insulation refers to a polyurethane-based foam providing high R-value per inch.
Spray foam insulation was used in the walls for its high thermal resistance.


Which is more cost-effective, fiberglass or spray foam insulation?

Fiberglass is generally more affordable than spray foam.

What is fiberglass insulation?

It's an insulating material made from fine glass fibers, used for thermal and sound insulation.

How long do these insulations last?

Fiberglass can settle over time, while spray foam maintains its shape and effectiveness longer.

What is spray foam insulation?

A chemical mixture that expands into a foam, used for sealing and insulating buildings.

Can both insulations be used in all areas of a building?

Fiberglass is versatile for various areas, while spray foam is ideal for gaps and hard-to-reach spaces.

How are fiberglass and spray foam insulation different in installation?

Fiberglass is installed as batts or rolls, while spray foam is sprayed into place.

Are there environmental concerns with either insulation type?

Fiberglass can be itchy and often contains recycled materials; spray foam produces off-gassing during application.

Can I install these insulations myself?

Fiberglass can be a DIY project, but spray foam typically requires professional installation.

Does spray foam insulation expand after application?

Yes, it expands to fill and seal spaces.

Can these insulations be combined in a single project?

Yes, they can be used together for optimal results in certain applications.

Is spray foam insulation fire-resistant?

It generally has fire-retardant properties, but check specific product ratings.

Can fiberglass insulation be recycled?

Yes, it often contains recycled materials and can be recycled.

How do the R-values of fiberglass and spray foam insulation compare?

Spray foam has a higher R-value per inch, making it more efficient.

Which insulation is better for soundproofing?

Fiberglass is commonly used for its sound-dampening properties.

Is either insulation type prone to mold or pests?

Spray foam resists moisture and pests better than fiberglass.

Does the thickness of the insulation affect its performance?

Yes, thicker layers generally provide better insulation.

How do I choose the right insulation for my home?

Consider factors like climate, area of application, and budget.

How does weather affect the performance of these insulations?

Both perform well in various climates, but spray foam offers better moisture resistance.

What safety precautions are needed when installing fiberglass insulation?

Protective gear is recommended to avoid irritation from the glass fibers.

Are there health concerns with either type of insulation?

Fiberglass can cause irritation; spray foam should be handled by professionals due to chemical exposure.
About Author
Written by
Janet White
Janet White has been an esteemed writer and blogger for Difference Wiki. Holding a Master's degree in Science and Medical Journalism from the prestigious Boston University, she has consistently demonstrated her expertise and passion for her field. When she's not immersed in her work, Janet relishes her time exercising, delving into a good book, and cherishing moments with friends and family.
Edited by
Aimie Carlson
Aimie Carlson, holding a master's degree in English literature, is a fervent English language enthusiast. She lends her writing talents to Difference Wiki, a prominent website that specializes in comparisons, offering readers insightful analyses that both captivate and inform.

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