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Energy Efficiency

Does Your Home’s Insulation Measure Up?

Keep your home warm and your heating costs low

Just as a hat and coat provide insulation for your body against the cold, attic insulation does the same for your home.

When your home is not properly sealed and insulated, cold air sneaks in and heat escapes, making your heating system work harder and your home less comfortable. Effectively sealing and insulating your home can cut your heating and cooling costs by an average of 15 percent.

Your attic is one of the first places you should consider insulating, particularly because most homes do not have enough attic insulation.

Insulation is graded by its R-value—the higher the R-value, the greater the insulating power. If you live in a mild climate, your attic insulation should have a minimum rating of R-38, or about 13–14 inches of insulation. If you live in a colder climate, aim for a minimum value of R-49, or about 16–18 inches of insulation.

How can you tell if your attic needs more insulation? As a general rule, if you go into your attic and can see the ceiling joists on the attic floor, there is not enough insulation.

If you live in an older home, be sure the wiring is in good shape, too. If it’s not, the wiring should be replaced before adding insulation.

Whether you hire a contractor or undertake adding insulation as a do-it-yourself project, first:

  • Seal any air leaks, including those around exposed air ducts and the attic door or hatch.
  • If you have existing attic insulation, it is usually not necessary to remove it unless it is wet, moldy or contains animal waste.
  • Make sure there is sufficient ventilation in the attic. Warmth and moisture can build up in an improperly ventilated attic, which can lead to roof problems.

There are two types of insulation that you could place on your attic floor: batt or roll (also known as blanket) insulation and blown-in or loose-fill insulation. Blown-in insulation requires special equipment to install but fills the space better than batt or roll insulation, which can leave gaps without careful placement around ceiling joists, vents and other impediments.

Insulation is most commonly made from fiberglass, cellulose or mineral wool. Many energy advisers recommend blown-in cellulose insulation due to its superior coverage, high R-value and air-sealing abilities. Blown-in cellulose insulation is treated with boric acid, which acts as a fire retardant and insect repellent.