Insulation R-Value Chart — Ontario

Different insulation materials offer varying thermal resistance per inch of thickness, along with distinct advantages and limitations that make them suitable for specific applications. Understanding these characteristics helps contractors and homeowners select the most cost-effective and performance-appropriate solution for each building element. The R-value per inch represents the material's thermal resistance when properly installed, though real-world performance depends heavily on installation quality, air sealing, and moisture management.

The Ontario Building Code's Supplementary Standard SB-12 establishes minimum thermal resistance requirements based on climate zones, which correlate to heating degree days. The Greater Toronto Area and much of southern Ontario falls within Climate Zone 5 (approximately 4,000 heating degree days), while regions like Ottawa and northeastern Ontario fall into Climate Zones 6 and 7 (5,000+ and 6,000+ heating degree days respectively). These are minimum requirements—exceeding them often provides better long-term energy savings and comfort.

Note that effective R-values must account for thermal bridging through framing members; continuous exterior insulation significantly improves whole-wall R-values by reducing thermal bridging.

Insulation costs vary significantly based on material type, regional availability, project scale, and installation complexity. Material costs reflect bulk contractor pricing for standard residential quantities, while installed costs include labour, equipment, and associated expenses such as vapour barriers and air sealing. These figures represent typical costs in the GTA market as of 2026; remote locations or small-quantity purchases may see 15-30% premiums.

Lifespan assumes proper installation and normal building conditions—moisture infiltration, pest damage, or structural issues can significantly reduce these timelines. When evaluating costs, consider the total system performance including air sealing effectiveness, which often matters more than raw R-value for energy efficiency.

Selecting appropriate insulation requires matching material properties to specific building conditions, considering factors like moisture exposure, space constraints, budget, and performance goals. Each application presents unique challenges that favour certain insulation types over others.

Attics represent the most cost-effective location to add insulation, as heat rises and significant thermal losses occur through the roof assembly. For vented attics with adequate clearance, blown-in cellulose or fibreglass offers the best value, providing R-50 to R-60 coverage economically. Cellulose performs slightly better due to its higher R-value per inch (R-3.7) and superior air sealing properties as it settles into gaps. Ensure proper attic ventilation with soffit and ridge vents—Ontario Building Code requires 1:300 ventilation ratio.

Install baffles at soffits to maintain airflow channels. For cathedral ceilings or limited-height applications, closed-cell spray foam maximizes R-value in restricted depth, though at significantly higher cost. When topping up existing insulation, blown-in products work well over old fibreglass batts. For attics with mechanical equipment or storage needs, consider creating an insulated, conditioned attic space using spray foam at the roof deck—this approach costs 40-60% more but provides conditioned space and protects HVAC equipment from temperature extremes.

Always seal attic bypasses (plumbing penetrations, electrical boxes, chimney chases) before adding insulation, as air leakage can account for 30-40% of heat loss regardless of R-value.

Wall insulation selection balances cost, R-value requirements, and installation method. For new construction with 2×6 framing (140mm), standard R-20 fibreglass batts (5.5" thick) meet basic code requirements in Climate Zone 5 when combined with continuous exterior insulation. Mineral wool batts provide superior fire resistance and sound dampening—ideal for party walls in semi-detached homes or near bedrooms—at 25-35% cost premium.

For retrofit applications or situations requiring maximum R-value in 2×4 walls (89mm), closed-cell spray foam delivers R-24 in 4" depth while providing excellent air sealing and structural reinforcement. Many high-performance builds now use a hybrid approach: R-20 cavity insulation (fibreglass or mineral wool) plus R-5 to R-10 continuous exterior rigid foam, which dramatically reduces thermal bridging through studs and plates.

XPS or polyiso work well for exterior continuous insulation under siding, with polyiso offering higher R-value but requiring protection from cold-weather performance loss. Install careful air barriers at the sheathing or interior vapour barrier—air leakage through walls can reduce effective R-value by 20-50%. In Climate Zones 6 and 7, plan for R-20 cavity plus R-7 continuous insulation to meet code minimums, or consider advanced framing techniques (24" on-centre studs, insulated headers) to improve thermal performance while reducing lumber costs.

Below-grade insulation faces unique moisture challenges requiring vapour-resistant materials and careful detailing. For exterior basement insulation (preferred method), XPS rigid foam provides optimal moisture resistance and consistent R-value when wet—install R-12 continuous (2.5" XPS) in Climate Zone 5, extending from footing to grade. Protect above-grade portions with cement board, stucco, or parging.

For interior basement finishing, two proven approaches exist: 1) Interior rigid foam (1.5-2" XPS) against concrete wall, then framed wall with fibreglass batts (achieving R-20 total), or 2) 2-3" closed-cell spray foam directly on concrete (R-12 to R-20), which acts as its own vapour barrier and air seal. Closed-cell spray foam excels in basements due to moisture impermeability and ability to seal rim joists—often the greatest source of basement air leakage.

Never use vapour-permeable insulation like open-cell foam or unfaced fibreglass directly against concrete, as moisture migration will cause mould growth. For walkout basements or above-grade portions, treat as standard above-grade walls with full insulation and vapour barrier. Always address bulk water management (perimeter drainage, proper grading, eavestroughs) before insulating—insulation cannot solve water infiltration problems. In retrofit situations with limited floor-to-ceiling height, closed-cell spray foam maximizes R-value per inch.

Apply spray foam directly to clean, dry concrete; repair major cracks first with hydraulic cement or epoxy injection.

Crawlspace insulation strategy depends on whether the space is vented or unvented (conditioned). For traditional vented crawlspaces, insulate between floor joists with R-31 fibreglass batts or mineral wool, supporting insulation with netting or furring strips to prevent sagging—sagging reduces R-value by creating air gaps and compressing insulation. Ensure foundation vents provide adequate airflow (1:150 ventilation ratio) to prevent moisture buildup.

For unvented crawlspaces (increasingly preferred for superior moisture control and energy performance), insulate foundation walls rather than floor above, creating a conditioned space. Apply R-12 to R-15 continuous insulation to crawlspace walls using rigid foam or closed-cell spray foam, extending from sill plate to footing. Cover crawlspace floor with 6-mil polyethylene vapour barrier, lapping seams 300mm and sealing to walls.

This approach keeps supply ducts and plumbing within conditioned space, prevents frozen pipes, and reduces moisture problems common in vented crawlspaces. Unvented crawlspaces require mechanical ventilation or connection to home's HVAC system—install supply register providing approximately 1 CFM per 50 square feet of crawlspace area. Pay special attention to rim joist insulation in both approaches—this area accounts for significant heat loss.

Use closed-cell spray foam or rigid foam cut precisely to fit rim joist cavities, sealing all gaps with caulk or spray foam. In flood-prone areas, use moisture-resistant insulation (XPS, closed-cell spray foam) and maintain adequate clearance above potential water levels.