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What R-value should I use for attic insulation?

Short answer

Use the official zone for the project and the applicable country table: ENERGY STAR varies U.S. recommendations by zone and existing insulation condition, while NRCan publishes Canadian minimum roof/ceiling RSI and R values by zone.

A postal code or county should be mapped through current official material, not guessed from a representative city. The desired whole assembly and an added product-label R-value are different quantities.

  • U.S. table: Zone 1 R30; Zone 2–3 R49; Zone 4A/4B and higher groups R60 for uninsulated attics.
  • Canadian minimums shown by NRCan range from R45 in Zone 4 to R80 in Zones 7a–8.
  • Inspect and air-seal before choosing a top-up.

Formula or decision boundary

planning gap = official target for zone/condition − assessed existing performance; product selection must use an exact label row

Country lookup boundary

Country lookup boundary
CountryZone sourceCondition input
United StatesPNNL/DOE county lookup and ENERGY STAR tableuninsulated or existing 3–4 in
CanadaNRCan climate-zone tableroof/ceiling strategy and assembly condition

Use the answer

  1. Identify the official zone

    Use county data in the U.S. or NRCan/local guidance in Canada.

  2. Inspect the assembly

    Record existing material, depth, condition, air leaks, moisture, and hazards.

  3. Select an exact product row

    Translate the project into a label-supported added R-value without interpolating coverage.

Safety and scope

  • Do not disturb vermiculite or suspect asbestos-containing material.
  • Resolve moisture, wiring, combustion, and fixture-clearance issues before covering them.

Sources and scope

Source links reviewed July 16, 2026. A review date is not the document's publication date.

  1. ENERGY STAR: Recommended Home Insulation R-ValuesUnited States · government guide

    Recommendations are presented by ENERGY STAR using 2021 IECC climate zones.

  2. Pacific Northwest National Laboratory: Guide to Determining Climate Zones by CountyUnited States · government standard

    Use the county files for a project address; representative cities are examples rather than boundaries.

  3. Natural Resources Canada: Keeping the Heat In — How your house worksCanada · government guide

    Canadian guidance uses effective thermal resistance and climate-zone classifications.

  4. Natural Resources Canada: Keeping the Heat In — Roofs and atticsCanada · government guide

    Follow product labels for bag count and settled depth; do not disturb suspected vermiculite.