How to Add Insulation to Your Attic

Adding attic insulation involves measuring your current insulation depth, choosing the right type (batts, blown-in, or spray foam), and installing it to achieve R-38 to R-60 depending on your climate zone.

  1. Know Your Starting Point. Measure the depth of existing insulation with a ruler. If it's less than 10 inches, you need more. Check for gaps, compressed areas, or moisture damage. Take note of any air leaks around light fixtures, vents, or penetrations in the ceiling below.
  2. Size Your Project Right. Determine your climate zone's recommended R-value (typically R-38 to R-60 for most areas). Measure your attic's square footage. If adding to existing insulation, calculate only what's needed to reach the target R-value. Most bags of insulation show coverage area on the label.
  3. Pick Your Material Wisely. Fiberglass batts work well for standard joist spacing and DIY installation. Blown-in cellulose or fiberglass offers better coverage around obstacles. Spray foam provides the best air sealing but costs more. For most homeowners, unfaced fiberglass batts are the easiest starting point.
  4. Gear Up Before Entering. Wear long sleeves, pants, gloves, safety glasses, and a dust mask or respirator. You'll need a utility knife, measuring tape, staple gun, and temporary lighting. Lay plywood sheets across joists to create a safe walking surface.
  5. Stop Air Leaks First. Use caulk or expanding foam to seal gaps around pipes, wires, and ductwork. Install weatherstripping around the attic access door. This step is crucial because air leaks can reduce insulation effectiveness by up to 40 percent.
  6. Roll Out the Insulation. Start at the furthest point from the attic entrance and work toward the exit. For batts, cut them slightly wider than joist spaces and let them spring into place without compressing. Don't cover recessed lights or exhaust fans. Maintain the manufacturer's recommended thickness.
  7. Let Your Attic Breathe. Install baffles between rafters at the eaves to maintain airflow from soffit vents. Keep insulation at least 3 inches away from recessed lights unless they're IC-rated. Never block ridge vents, gable vents, or soffit vents with insulation.
  8. Document Your Achievement. Verify even coverage with no gaps or compressed areas. The insulation should be level with or slightly above the tops of the joists. Mark the attic access with the installation date and R-value achieved for future reference.