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

Fiberglass or spray foam? How to choose.

You're here because you have questions.

  • Does it really matter what type of insulation I have in my home?
  • With all the other decisions I have to make, do I really have to be involved in this one?
  • Shouldn't my builder or contractor know best?

We get it, but you're here because something's telling you your insulation does matter, that you really should be involved in the decision. Your builder or contractor does have valuable information and advice, but ultimately, the decision is yours … because no one cares more about your family's comfort than you do.

In homebuilding and home repair/remodeling situations, your insulation choices may come down to fiberglass or spray polyurethane foam (SPF). They can keep your home equally comfortable temperature-wise, but there are other criteria to consider.

Here’s a table that shows a side-by-side comparison of key factors to consider when you’re selecting your home insulation.

Fiberglass or spray foam? How to choose.

You're here because you have questions.

  • Does it really matter what type of insulation I have in my home?
  • With all the other decisions I have to make, do I really have to be involved in this one?
  • Shouldn't my builder or contractor know best?

We get it, but you're here because something's telling you your insulation does matter, that you really should be involved in the decision. Your builder or contractor does have valuable information and advice, but ultimately, the decision is yours … because no one cares more about your family's comfort than you do.

In homebuilding and home repair/remodeling situations, your insulation choices may come down to fiberglass or spray polyurethane foam (SPF). They can keep your home equally comfortable temperature-wise, but there are other criteria to consider.

Here’s a table that shows a side-by-side comparison of key factors to consider when you’re selecting your home insulation.

 FiberglassSpray Polyurethane Foam
DerivationMineral and recycled-glass-basedPetrochemical-based
IngredientsFiberglass main ingredients are sand, borax, soda ash, limestone, carbohydrate-based binder, and recycled glass. Formaldehyde-free home insulation.
  • Formula has two main components, an "A side" and "B side."
  • A side: Isocyanates
  • B side: Typically a proprietary blend of polyols, catalysts, blowing agents, surfactants and flame retardants1

Health and safety testingThe most thoroughly tested insulation product for long-term health and safety impacts.

The following summarizes the health findings by agency:

Health Canada 1993

National Academy of Sciences (NAS) 2000

International Agency for Research on Cancer (IARC) 2002

Agency for Toxic Substances and Disease Registry (ATSDR) 2004

National Toxicology Program (NTP) 12th RoC 2011

California Office of Environmental Health Hazard Assessment (OEHHA) 2011
Tested. Chemical emissions can potentially be intensified by the application temperature being too cold, material installed too quickly, wet surfaces, frost on surfaces, improperly maintained equipment, improper proportioning, and the age of the drums containing the product.
Indoor air qualityFormaldehyde-free building insulation and certified to meet stringent IAQ benchmarks.
  • Potential off-gassing during installation. Isocyanates are known allergic sensitizers. Once sensitized, even minute amounts can induce adverse reactions.2
Installation concernsPossible mechanical irritation (itchiness) to skin, nose, throat. Minimal protective gear required.
  • Isocyanate exposure may cause skin, eye and lung irritation, asthma and allergic sensitization.3
  • Recommends anyone not wearing protective gear evacuate the site until the spray foam is fully cured.
  • Improper application can pose a fire hazard.
SustainabilityContains 40% to 60% recycled glass.Some recycled content.*
*Icynene closed-cell SPF (MD-R-200) contains up to 12.6% recycled plastic. Others also claim small amounts of recycled content.
Fiberglass
Derivation
Mineral and recycled-glass-based
Ingredients
Fiberglass main ingredients are sand, borax, soda ash, limestone, carbohydrate-based binder, and recycled glass. Formaldehyde-free home insulation.
Health and safety testing
The most thoroughly tested insulation product for long-term health and safety impacts.

The following summarizes the health findings by agency:

Health Canada 1993

National Academy of Sciences (NAS) 2000

International Agency for Research on Cancer (IARC) 2002

Agency for Toxic Substances and Disease Registry (ATSDR) 2004

National Toxicology Program (NTP) 12th RoC 2011

California Office of Environmental Health Hazard Assessment (OEHHA) 2011
Indoor air quality
Formaldehyde-free building insulation and certified to meet stringent IAQ benchmarks.
Installation concerns
Possible mechanical irritation (itchiness) to skin, nose, throat. Minimal protective gear required.
Sustainability
Contains 40% to 60% recycled glass.
Spray Polyurethane Foam
Derivation
Petrochemical-based
Ingredients
  • Formula has two main components, an "A side" and "B side."
  • A side: Isocyanates
  • B side: Typically a proprietary blend of polyols, catalysts, blowing agents, surfactants and flame retardants1
Health and safety testing
Tested. Chemical emissions can potentially be intensified by the application temperature being too cold, material installed too quickly, wet surfaces, frost on surfaces, improperly maintained equipment, improper proportioning, and the age of the drums containing the product.
Indoor air quality
  • Potential off-gassing during installation. Isocyanates are known allergic sensitizers. Once sensitized, even minute amounts can induce adverse reactions.2
Installation concerns
  • Isocyanate exposure may cause skin, eye and lung irritation, asthma and allergic sensitization.3
  • Recommends anyone not wearing protective gear evacuate the site until the spray foam is fully cured.
  • Improper application can pose a fire hazard.
Sustainability
Some recycled content.*
*Icynene closed-cell SPF (MD-R-200) contains up to 12.6% recycled plastic. Others also claim small amounts of recycled content.

Performance

Thermal performance is the main reason to insulate, of course. You need something in the walls to help keep warm and cold air where you want them, either inside or outside. Insulation "resists" the transfer of heat from one side of a material to the other. The measurement for that resistance is known as a material's R-value. The higher its resistance, the higher the R-value, and the higher the R-value, the greater the insulating power. It doesn’t matter what kind of insulation you're talking about. R-13 is R-13, whether it's fiberglass, spray foam or any other insulation.

But there are other things to consider besides thermal performance. Things like cost and ease of installation. And things like what problems you might run into if you ever want to remodel or need to make repairs to the electrical or plumbing lines running behind your walls. Here's the side-by-side comparison of some important performance and installation considerations.

Home Insulation Performance Factors

 FiberglassSpray Polyurethane Foam
Estimated installed per square foot cost @ R-19$1.00 - $1.88$3.10 - $9.54 (Open cell)

$3.02 - $5.20 (Closed cell)
InstallationSimple. Suitable for DIY.Complex. Requires:
  • Special training
  • Extensive personal protective equipment
  • On-site mixing of chemicals
  • Strict adherence to temperature and humidity guidelines
  • Not suitable for DIY
Thermal performanceR-values are independent of insulation type. R-13 fiberglass insulation provides the same thermal performance as R-13 spray foam insulation.
Air sealingWhen paired with standard air sealing practice (i.e., taped house wrap or caulk or spray sealant), air infiltration is effectively zero.With standard air sealing practices, air infiltration is effectively zero.
Repair/remodeling issuesBatts and rolls are easily removed and replaced as needed for electrical and plumbing repairs.Potentially difficult. Foam often must be cut or chiseled out then replaced.
Fiberglass
Estimated installed per square foot cost @ R-19
$1.00 - $1.88
Installation
Simple. Suitable for DIY.
Thermal performance
R-values are independent of insulation type. R-13 fiberglass insulation provides the same thermal performance as R-13 spray foam insulation.
Air sealing
When paired with standard air sealing practice (i.e., taped house wrap or caulk or spray sealant), air infiltration is effectively zero.
Repair/remodeling issues
Batts and rolls are easily removed and replaced as needed for electrical and plumbing repairs.
Spray Polyurethane Foam
Estimated installed per square foot cost @ R-19
$3.10 - $9.54 (Open cell)

$3.02 - $5.20 (Closed cell)
Installation
Complex. Requires:
  • Special training
  • Extensive personal protective equipment
  • On-site mixing of chemicals
  • Strict adherence to temperature and humidity guidelines
  • Not suitable for DIY
Thermal performance
R-values are independent of insulation type. R-13 fiberglass insulation provides the same thermal performance as R-13 spray foam insulation.
Air sealing
With standard air sealing practices, air infiltration is effectively zero.
Repair/remodeling issues
Potentially difficult. Foam often must be cut or chiseled out then replaced.

Now that you know the main differences between fiberglass and spray foam insulation, you can have an informed conversation with your builder or contractor to select the product that's right – and safe – for your family.

Find more information and get help starting the conversation with your builder or contractor.