Attic Insulation: Savings From the Top Down

Proper attic insulation can keep your energy dollars from going through the roof.


Adding insulation to the attic is one of the most cost-effective ways a homeowner can save energy. In addition to reducing heat loss in the winter and heat gain in the summer, attic floor insulation improves comfort by providing even temperature distribution throughout the house. To optimize energy savings and maximize comfort, insulation must be installed properly.

Attic insulation techniques

Attic insulation is typically installed as loose-fill or as batts that are attached to the joists. Although installation costs vary, blowing loose-fill attic insulation — fiberglass, rock wool or cellulose — is usually less expensive than installing batts and provides better coverage.

Attic floors over flat ceilings are often the easiest part of the home to insulate. They are usually accessible and have ample room for insulation. However, many homes have cathedral ceilings or attic knee walls that present unique insulation requirements.

Some key steps for ensuring proper installation include:

  • Seal all attic air leaks, especially chases, dropped ceilings, wiring and plumbing penetrations, light fixtures and bathroom fans. Insulation typically doesn't stop air flow.
  • Install blocking (metal flashing) to maintain clearance requirements (usually 3 inches) for heat-producing equipment found in an attic, such as flues, chimneys and exhaust fans.
  • Use only insulated ceiling-rated recessed lights which are airtight and can be covered with insulation.
  • Select insulation levels that meet or exceed the recommended R-values.
  • Locate the attic access in an unconditioned part of the house if possible. Otherwise, weatherize the attic access and insulate it by attaching insulation to the cover or by installing an insulated cover box.
  • If mechanical equipment or storage areas are located in the attic, elevate the attic decking to allow full-height insulation to be installed.

Ensure complete coverage for attic insulation. If you're using loose-fill insulation, follow the manufacturer's specifications to obtain coverage at consistent depths. Make sure the installer provides attic rulers to indicate proper blown depth and an accurate attic report card showing that sufficient density was installed.

When using batt insulation, make sure the batts completely fill the joist cavities. If joists are uneven, patch gaps with scrap pieces. Overall, a complete and even installation is necessary to ensure optimal effectiveness and to maximize your savings.