Measure and MendStart measuring

Insulation

Attic insulation top-up

The calculator estimates material for an added labeled layer; it does not claim that nominal R-values of old and new materials simply become an exact whole-assembly performance. U.S. and Canadian products use separate coverage charts and must never be substituted for each other.

First answer

First inspect and air-seal the attic, identify the current insulation, choose an added R-value that exactly appears on the applicable AttiCat label, then divide attic area by that row’s maximum coverage per bag and round up.

Run the calculator

Formula or decision rule

attic area ÷ exact-label maximum coverage per bag, rounded up; also honor a published minimum bags/1,000 ft²
  • Interpolation between label rows is rejected.
  • The result reports the label minimum installed thickness.
  • Match the market, product, bag, and coverage chart before purchase.

Top-up decision order

Top-up decision order
StageDecisionEvidence
Inspectmaterial, depth, condition, hazardsENERGY STAR / NRCan
Comparecurrent condition to zone guidanceofficial climate table
Selectexact added R label rowAttiCat market label
Calculatearea ÷ max coveragewhole bags

Work through the project

  1. Inspect without disturbing suspect material

    Record insulation type, representative depth, blocked vents, moisture signs, wiring, and heat-producing fixtures.

  2. Seal first

    Address air leakage and moisture pathways using the applicable official attic guidance before covering them.

  3. Use one exact label

    Select the U.S. or Canadian AttiCat chart that matches the bags sold for the project and meet its coverage and thickness requirements.

Safety and scope

  • Do not disturb vermiculite or other suspect asbestos-containing material.
  • Use a qualified professional for unsafe access, knob-and-tube wiring concerns, active moisture, combustion venting, or other conditions outside a straightforward top-up.

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. ENERGY STAR: DIY Checks and InspectionsUnited States · government guide

    Do not disturb suspected vermiculite insulation; obtain qualified guidance before work.

  3. ENERGY STAR: Attic InsulationUnited States · government guide

    Air leaks and moisture conditions should be addressed before insulation is added.

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

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

  5. 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.

  6. Owens Corning: AttiCat Expanding Blown-In Insulation SystemUnited States · manufacturer data sheet

    Calculator accepts only labeled table R-values and rounds the label bag requirement up.

  7. Owens Corning Canada: AttiCat Expanding Blown-In Insulation System and coverage chartCanada · manufacturer data sheet

    The official product page publishes the coverage chart and links the identified Coverage Card; use the Canadian label, never the U.S. table, and verify the current bag at purchase.