Attic Insulation

Insufficient insulation is one of the leading sources of wasted energy in most homes, along with air leakage. And one of the easiest places to add insulation is your attic.

A properly insulated attic is a key element of your home’s “thermal envelope”—the barrier between the heated and cooled interior and the outside. If the thermal envelope is inadequate, you’re wasting energy on heating and cooling, which can equal over half your home’s energy costs. Adding proper insulation could save you 20% on your energy bills.

Benefits of Attic Insulation

  • Slows heat loss and gain, conserving energy, reducing utility bills and improving temperature control and comfort.
  • Reduces the size/power of heating/cooling equipment required.

What You Should Know

Insulation is measured by R-values, which indicate its ability to resist heat flow, with higher values representing better performance. Most attics should be insulated to about R-38, or to a depth of 10-14 inches depending on the insulation type. The eScore program requires minimum R-values of:

  • Attic Floor: R-38
  • Kneewalls: R-18
  • Attic Access: R-10

Before Beginning Work

  • Seal the attic for air leaks before adding insulation.
  • Repair any ceiling problems, water leaks, vent leaks or other problems.
  • Remove any items stored in the attic.
  • If your home has an attached garage or gas appliances, install a carbon monoxide monitor.

General Guidelines

  • Use insulation appropriate for the area, such as rigid foam insulation on the outer side of the knee wall supporting rafters and dense pack insulation for decked attic floors.
  • Level out loose-pack insulation and install depth markers every 300 square feet.
  • Provide at least 3 inches clearance for any lighting not rated for contact with insulation, wiring or combustion vents.
  • Seal any ducts and insulate them to R-8.
  • Vent range hoods, clothes dryers, and bathroom exhaust fans outside the thermal envelope.
  • Install ventilation (not powered) to remove heat and moisture from the attic.


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