Comparing Insulation Types

When considering insulation for your project, it’s important to understand the facts about different product types and options. First thing’s first: there is no such thing as a “best insulator”. Surprised? According to the Building Sciences Corporation (BSC), all insulation types perform equally well when properly installed and air sealed.

Understanding different insulation materials

There are four main types of insulation products on the market today used for attics and wall cavities: fiberglass, rock or slag wool, cellulose, and spray foam. Each of these options has different qualities and attributes that may inform your choice of materials. Additionally, Extruded Polystyrene (XPS), Expanded Polystyrene (EPS), Polyisocyanurate (PIR), and Polyurethane (PUR) Boards are common in both continuous sheathing and under slab applications. This section focuses on the former.

Fiberglass insulation: Made from glass cullet and other raw materials which are melted and spun into fibers that resemble the texture of wool.  It comes in batts, rolls, or loose-fill forms and is commonly used in sidewalls, attics, floors, crawl spaces, cathedral ceilings, and basements.

Stone, rock, or slag wool insulation: Made from rock, blast furnace slag, and other raw materials which are melted and spun into fibers to resemble the texture of wool. Mineral wool comes in batts, rolls, or loose-fill forms. Like fiberglass, it is also used in sidewalls, attics, floors, crawl spaces, cathedral ceilings, and basements.

Stone and slag wool insulation are comprised of basically the same raw materials, are produced in the same ways, and produce fairly similar performance attributes.  The major difference is in the specific volumes of the various raw materials used to make each product.

Cellulose insulation: Composed mostly of cellulose fibers usually derived from paper, paperboard stock, or wood, and made with or without binders. Cellulose is chemically treated to resist fire, but the application process isn’t standardized, and there is evidence that the fire resistance wears off over time.[i]

Spray foam insulation: Chemical-based insulation that is mixed on-site to create foam, and applied with a sprayer in attics and into wall cavities. The two main types of spray foam insulation are open cell and closed cell. The properties of each are somewhat different.

There are many factors that may influence the quality of spray foam products, including:

FeaturesFiberglassMineral WoolSpray FoamCellulose
Value and Energy SavingsThe type of insulation material you choose has little impact on your energy savings. There are 3 things that impact the efficiency of your insulation and the return on your investment:

• correct installation
• proper air sealing
• getting the most insulation R-value per dollar

R-value is simply a material’s capacity to resist heat flow. The higher the insulation R-value, the greater the insulating power. Any material of the same R-value will insulate equally well if installed and sealed correctly.
Thermal Performance
2 x 4” wall (3.5”)
R-12 to R-14[iii]
2 x 6” walls (3.5”)
R-19 to R-24[ii]
2 x 4” wall (3.5”)
R-12 to R-15[ii]
2 x 6” walls (3.5”)
R-12 to R-24[ii]
2 x 4” wall (3.5”)
2 x 6” walls (3.5”)
2 x 4” wall (3.5”)
2 x 6” walls (3.5”)
Thermal Performance
2 x 4” wall (3.5”)
R-12 to R-14[ii]
2 x 6” walls (3.5”)
R-19 to R-24[ii]
2 x 4” wall (3.5”)
2 x 6” walls (3.5”)
2 x 4” wall (3.5”)
R-12 to R-22[iv]
2 x 6” walls (3.5”)
R-19 to R-35
2 x 4” wall (3.5”)
R-12 to R-13
2 x 6” walls (3.5”)
R-19 to R-20
Air SealingRequired to work properlyRequired to work properlyProvides some air sealing if applied properly, but no insulation product has been proven to provide a continuous, whole-home air barrier. [v]Required to work properly
Installation Batts: option to DIY
Blown-In: professional installation is recommended. The installer must use a machine capable of installing fibre glass or mineral wool. Some grades of mineral wool can be poured.
Requires professional installation, and inhabitants are required to vacate the premisesDry application: option to DIY
Wet application: Requires professional installation with a blowing machine to add water
SettlingBatts: No settling
Blown-In: Virtually no settling[vi]
Batts: No settling
Blown-In: Virtually no settling[vi]
Shrinkage over time[vii]Batts: N/A
Blown-In (dry): Can settle up to 20% in attics[vi]
Health ImpactsProven track record for safe use. 90% of product in residential market today is formaldehyde free. [viii]Thoroughly tested product[ix]A main ingredient in spray polyurethane foam insulation, methylene diphenyl diisocyanate, has inherent health risks[x]Very limited health and safety testing
Recycled Content and Renewable ResourcesContains upwards of 70% recycled glass, and sand, a renewable and abundant resourceSlag wool contains 10-15% recycled content, and rock wool contains 70-90%. Both contain minerals like basalt or diabase and blast furnace slag, limestone, or dolomiteNoneContains 80% or more recycled content, including newspapers or wood fibre
Fire SafetyNaturally fire resistant, but faced insulation will contribute to flame spread unless flame-resistant materials are used[xii]. Can resist melting up to 1300ºF (704ºC).Naturally fire resistant, and can resist melting up to 2,150ºF (1177ºC)Can be consumed by flame and will ignite at 371ºC (700ºF)[xiii]. Exposed foam should be protected using a Class B thermal barrier, i.e., gypsum or some mineral fiber products.Naturally flammable. Manufacturers must apply 20%, by weight, of fire retardants
Moisture[xv]No insulation product alone is capable of preventing moisture-related problems in the home. Home moisture management is complex—it’s about letting moisture in, letting it out, and giving it the chance to evaporate.
MouldMould is a product of moisture and the presence of food (any organic material) for mould spores. Any moisture issues should be addressed immediately.

Note: Some insulation products advertise “mould resistance”, but mould growth can occur on ANY surface if there is water and food present. No product can prevent mould.


[i] Environmental Cycling of Cellulosic Thermal Insulation and Its Influence on Fire Performance

[ii] Thermal Performance: Many insulation advertisements make R-value per inch claims. The R-value Rule specifically prohibits such claims with two exceptions: 1) an FTC Cease and Desist Order applies to you but differs from the Rule; and 2) you possess actual test results that prove the R-value per inch of your product does not drop is it gets thicker. R-values are not always linear, and, therefore, an insulation product’s thermal resistance may not be accurately represented by reference to the R-value per inch. An advertiser may list a range of R-value per inch. If such a claim is made, the advertiser must state exactly how much the R-value drops with greater thickness and include specific language with the claim. 16 C.F.R § 460.20.

[iii] Thermal performance ranges for fibre glass batt insulation in 2 x 4 and 2 x 6 walls found in manufacturers data and submittal sheets (2008, 2009).

[iv] Thermal performance ranges for open and closed cell foam spray-in insulation for 2 x 4 and 2 x 6 walls found in manufacturers data and submittal sheets (2009). In addition, calculations made by taking the R-value per inch value that is contained in the ASHRAE Handbook of Fundamentals, page 25.6 – 2005 edition.

[v] NAHB Research Center Inc. (1997) “Field Demonstration of Alternative Wall Insulation Products”. Prepared for the U.S. Environmental Protection Agency

[vi] U.S. Department of Energy, Energy Efficiency and Renewable Energy, “A Consumer’s Guide to Energy Efficiency and Renewable Energy: Loose-Fill Insulation”; Svennerstedt, Bengt (1990) “Field Data on Settling in Loose-Fill Thermal Insulation” in Insulation Matierals, Testing and Applications, D.L. McElroy and J.F. Kimpflen, eds.

[vii] Foams are not UV stable and can be biodegraded by sunlight. Bynum, Jr., R.T. (2001) Insulation Handbook, New York: McGraw-Hill, p.195, 199-200

[viii][viii] It’s important to know that the Consumer Product Safety Commission has determined that “fibrous glass insulation and ceiling tiles would have little impact on in-home formaldehyde levels” [Consumer Product Safety Commission Memorandum (1983) Summary of the Formaldehyde in Products Project]. The International Agency for Research on Cancer (IARC), the US National Toxicology Program (NTP), and the California Office of Environmental Health Hazard and Assessment have all stated that fibre glass and mineral wool thermal and acoustic insulations are not considered classifiable as carcinogens. You may still see claims about fibre glass being a carcinogen, but major US and global health bodies have made their views clear (NAIMA Publication N040, “Health and Safety Facts for Fiber Glass”).

[ix] Davis, J.M.G. (1993) “The need for standardized testing procedures for all products capable of liberating respirable fibres: the example of materials based on cellulose” in British Journal of Industrial Medicine, p. 187-190

[x] California Department of Toxic Substances Control

[xi] Reusability: Wet or damaged insulation of any type should not be reused.

[xii] Bynum, Jr., R.T. (2001) Insulation Handbook, New York: McGraw-Hill, p. 131

[xiii] Bynum, Jr., R.T. (2001) Insulation Handbook, New York: McGraw-Hill, p. 147

[xiv] APFA (2000) Thermal Barriers for the Spray Foam Industry

[xv] To maintain stable performance, insulation of any kind should not be exposed to water. Building codes require vapour retarders to be installed on the “warm-in-winter” side of most walls in cold climates, except on basement walls, the part of any wall below grade and any wall where moisture or freezing will not damage the materials. Refer to local building codes for specific vapour retarder requirements as they may not be the same as the model building codes.