Types of Home Insulation: Materials, R-Values, and Applications

Residential insulation in Canada is not a single product category. Five distinct material families are in common use, and each behaves differently with respect to heat flow, air movement, moisture, fire, and ease of installation. Understanding these differences matters for anyone assessing an existing assembly or specifying a new one.

The thermal resistance of insulation is expressed as an R-value (in imperial units) or RSI (in metric). The National Building Code of Canada 2020 sets minimum effective R-values for building envelope components, not just nominal R-values. The effective value accounts for the thermal bridging created by framing members, which reduces whole-wall performance compared to the rated R-value of the insulation alone.

Fiberglass Batts and Rolls

Fiberglass batts are the most widely installed residential insulation in Canada and the United States. The material consists of glass fibres bonded into a semi-rigid blanket, available in thicknesses to suit 2×4 (R-12 to R-14) and 2×6 (R-19 to R-22) framing. Rolls cover longer runs without seams.

The material is vapour-permeable. Unfaced batts allow moisture to pass through; kraft-faced versions have a paper vapour retarder on one side. In most Canadian climate zones, a separate polyethylene vapour barrier is installed on the warm side of the insulation, which makes the facing largely redundant in new construction.

Fiberglass performs best in well-sealed cavities where air movement through the batt is minimal. It provides no air barrier function on its own. In cathedral ceiling assemblies without an air barrier at the rafters, wind washing through the insulation can substantially reduce effective R-value in exposed locations.

Blown Cellulose

Cellulose insulation is produced from recycled paper products, treated with borate compounds for fire and pest resistance. It is installed by blowing loose fill into open attic floors or by dense-packing into wall cavities through a fill tube. Attic loose-fill cellulose is one of the most cost-effective approaches for increasing attic insulation depth in existing homes.

Dense-pack cellulose in walls achieves approximately R-3.7 per inch. At densities above a certain threshold, the material resists air movement through the cavity, which distinguishes it from loose-fill fiberglass in the same application. However, cellulose requires careful attention to moisture: the material can absorb and hold moisture if repeatedly wetted, which reduces its thermal performance and can lead to settlement.

Dense-pack cellulose at 3.5 inches (a 2×4 wall cavity) provides roughly R-13, comparable to a standard fiberglass batt but with substantially better resistance to air movement through the assembly.

Natural Resources Canada's Keeping the Heat In guide discusses cellulose as a retrofit insulation option for older wood-frame homes, noting its particular suitability for drill-and-fill installations where walls cannot be opened from the interior.

Mineral Wool

Mineral wool (also sold as rock wool or slag wool) is produced by melting basalt or blast-furnace slag and spinning the molten material into fibres. The resulting batts are denser and stiffer than fiberglass, with a nominal R-value of approximately R-3.7 to R-4.2 per inch depending on density.

The material is notable for two properties that set it apart from fiberglass in certain applications. First, it is dimensionally stable: mineral wool batts do not compress under their own weight and hold their shape in sloped or vertical cavities over time. Second, it is non-combustible. Mineral wool retains structural integrity at temperatures well above those that would melt glass fibres, which is why it is specified in fire-rated assemblies where insulation must remain in place during a building fire.

Mineral wool is also hydrophobic — water is repelled rather than absorbed, which makes it suitable for applications where occasional moisture exposure is possible, such as below-grade basement wall assemblies before a separate waterproofing layer is in place.

Rigid Foam Boards

Three types of rigid foam are used in residential construction: expanded polystyrene (EPS), extruded polystyrene (XPS), and polyisocyanurate (polyiso). Each has a different R-value per inch, moisture absorption characteristic, and environmental profile.

EPS achieves approximately R-3.8 per inch and is vapour-permeable at low densities. XPS provides around R-5 per inch and has lower moisture absorption than EPS, making it the conventional choice for below-grade foundation applications in Canada. However, XPS uses blowing agents with a high global warming potential; several manufacturers have shifted to lower-GWP alternatives in recent years.

Polyiso achieves the highest R-value per inch of the three — typically R-6 to R-6.5 — but its effective R-value decreases at cold temperatures, which affects its performance in Canadian cold climate applications at the exterior of wall assemblies.

Spray Polyurethane Foam

Spray polyurethane foam (SPF) is available in two formulations: open-cell (ocSPF) and closed-cell (ccSPF). They differ substantially in density, R-value, and moisture behaviour.

Open-cell SPF expands significantly on application and achieves approximately R-3.7 per inch. It is vapour-permeable and flexible once cured. Closed-cell SPF is denser, achieves R-6 to R-7 per inch, and functions as both an air barrier and a vapour barrier at sufficient thickness. In cold Canadian climates, closed-cell foam is commonly used on the interior face of rim joists and in unvented roof assemblies where its combined air sealing and insulating functions are both required.

SPF is applied by trained applicators as a two-component liquid. The exothermic reaction during curing requires the space to be vacated during and for a period after application. Improper mixing ratios or application temperatures outside the product's specified range can result in incompletely cured foam with reduced thermal performance.

R-Value Comparison

Selecting the Right Material

No single insulation material is optimal for all applications. The relevant considerations for a given installation include: the cavity depth and framing spacing available; the need for air barrier function; moisture exposure (particularly for below-grade assemblies); fire resistance requirements in the assembly; access constraints in retrofit situations; and the required R-value relative to the space available.

In practice, many high-performance Canadian homes use a combination of materials — for example, mineral wool batts between studs with a continuous layer of polyiso at the exterior, or closed-cell SPF at the rim joist combined with blown cellulose in the attic floor. The National Building Code's prescriptive compliance path specifies minimum R-values by climate zone; Part 12 of the NBC 2020 covers the energy efficiency requirements in detail.

Last updated: June 8, 2026. Source references: Natural Resources Canada — Keeping the Heat In; National Building Code of Canada 2020.