Calculate bags or batts for attic, walls, or crawlspace with North America R-value defaults.
To meet the minimum R-41 attic insulation requirement in North America (R-50+ recommended), you need approximately 13 inches of fiberglass batts, 10.7 inches of mineral wool, or 16 inches of blown-in fiberglass. Our calculator covers fiberglass batts, mineral wool, blown-in insulation, and rigid foam — with coverage, vapor barrier quantities, and compliance notes for Canadian and U.S. building codes.
Insulation is the single most cost-effective upgrade for reducing heating and cooling costs. A home that meets minimum R-value requirements will reduce annual energy costs by 10–20% compared to an uninsulated building. A home insulated to the recommended R-50 attic value can save $300–$600 per year in heating costs. The payback period on insulation upgrades is typically 3–7 years — one of the best returns on investment in home improvement.
R-value measures thermal resistance — how well a material resists heat flow. Higher R-values mean better insulation. R-value is additive: two layers of R-13 batts create R-26. In North America, provincial building codes specify minimum R-values significantly higher than U.S. minimums due to colder winters. The North America Construction Code requires a minimum of R-41 in attics (insulated ceilings), R-22 for exterior walls, and R-20 for floors over unheated spaces. The practical recommendation for North America new construction is R-50+ in attics for optimal energy performance.
Fiberglass batts are the most common insulation product for walls and attic floors. They come in standard widths to fit 16-inch and 24-inch stud and joist spacing. Common products: R-13 (3.5" thick, for 2×4 walls), R-20 (5.5" thick, for 2×6 walls), R-30 (9.5" thick, for attic floors), and R-38 (12" thick). Coverage is sold by the bag or roll. Fiberglass batts work best in framed cavities where they fill the space without gaps or compression — any compression or void reduces the effective R-value significantly.
Mineral wool (Roxul/Rockwool) offers superior performance over fiberglass in several areas: it's fire-resistant to 1,200°C, better at blocking sound transmission, and maintains its shape without sagging over time. It's also water-resistant — it won't absorb moisture and lose R-value in humid conditions. The trade-off is cost: mineral wool batts typically cost 40–60% more than fiberglass of equivalent R-value. For soundproofing, fire separation, or humid environments, mineral wool is worth the premium.
Blown-in (loose-fill) insulation is the preferred method for attic floors and adding insulation to existing finished walls without demolition. Blown fiberglass reaches approximately R-2.5 per inch; blown cellulose reaches approximately R-3.7 per inch. Coverage per bag varies by product and blowing machine settings — always use the coverage chart printed on the bag for your specific R-value target depth. Blown-in insulation conforms perfectly to irregular joist bays and around obstructions, eliminating the gaps that batts sometimes create around wiring and pipes.
Rigid foam boards (EPS, XPS, polyiso) are used for continuous insulation on exterior walls, insulating basement walls, under slabs, and as sheathing. XPS (extruded polystyrene — pink or blue boards) achieves R-5 per inch and is moisture-resistant, suitable for below-grade applications. EPS (expanded polystyrene) achieves R-3.85 per inch at lower cost. In cold climates, a vapor retarder (6 mil polyethylene is the standard in Canada) is installed on the warm side of the insulation to prevent warm, moist interior air from migrating into the wall cavity and condensing. The vapor barrier must be continuous and well-sealed at all edges, penetrations, and laps.
The North America Construction Code requires a minimum of R-41 for insulated ceilings (attic floors). Energy-efficient programs (Novoclimat, R-2000) recommend R-50 to R-60. Blown-in fiberglass at 16 inches achieves approximately R-42. To reach R-50, blow in approximately 20 inches of fiberglass or 14 inches of cellulose.
Yes. Adding blown-in insulation over existing batts is one of the most cost-effective energy upgrades. Before adding insulation, air-seal every penetration (light fixtures, plumbing, wiring, partition walls) with acoustical sealant or spray foam. Air sealing before adding insulation improves energy performance more than the additional R-value alone.
Yes, for heated basements and conditioned slabs. At least 2 inches of XPS foam under the slab and 2 inches on the perimeter (thermal break) dramatically reduces heat loss through the slab edge. The North America Construction Code requires slab-edge insulation for heated basements in new construction.
Going from R-20 to R-50 in the attic of a 1,500 sq ft house in North America typically saves $200–$400 per year in heating costs. Installed cost is approximately $1,500–$2,500 including air sealing, giving a payback period of 5–8 years. North America's Écoréno program may offer rebates — check reno-climat.com for current programs.
Fit batts snugly without compression — an R-20 batt compressed into an R-13 space provides R-13 performance, not R-20. Fill the entire cavity width and height without gaps. In 2×6 walls, use a full R-20 batt or two layers of R-10. Vapor barrier on the warm side (interior). Seal all penetrations through the barrier with acoustical sealant before drywalling.
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