Homeowner worried about asbestos insulation

Q: The home inspector who checked my house reported that the attic insulation is about 6 inches thick, but he didn't say whether it's made of fiberglass, asbestos or cellulite. I am concerned about possible asbestos. How can I determine the composition of this insulation?

A: Unless you've got a 6-inch layer of body fat in your attic, you definitely don't have "cellulite." However, it is possible that you have cellulose, a widely used form of attic insulation in older homes. Cellulose is easily recognized because it consists of finely shredded newspaper and looks somewhat like dry oatmeal.

Some homeowners express concern about the fire safety of paper-based insulation, but cellulose insulation is treated with a fire-retardant chemical to prevent combustion. When exposed to fire, the material may smolder briefly but will not support a flame.

Fiberglass insulation has the appearance of cotton candy or spun wool and is either blown into the attic in shredded form or is laid down in manufactured strips, commonly known as batts. When working in an attic that is insulated with fiberglass or cellulose, respiratory protection is advised to prevent inhaling airborne fibers or chemicals.

The use of asbestos as attic insulation is extremely rare. In 30 years of inspecting homes, I've encountered it on one occasion only, in the form of vermiculite, a material more commonly used to retain moisture in potting soil. Until the early 1970s, asbestos insulation was often used on air ducts in attics, but this material is not regarded as a health risk if it is in undamaged condition.

If you have reason to suspect loose asbestos of any kind in your attic, simply send a nickel-sized pinch in a plastic bag to an EPA-certified laboratory for analysis by polarized light microscope. If the result is positive, consult a certified asbestos inspector for an on-site evaluation.

Q: Last week, a sewer backup in our kitchen sink drained into the dishwasher, covering our dishes and tableware with a revolting, black film. This reminded us of something our home inspector had said when we originally purchased the home - something about an air device. Does this make any sense?

A: The plumbing code requires a simple device known as an "airgap" on dishwasher drain lines. The purpose of an airgap is to prevent a sewage backup from siphoning into your dishwasher. Home inspectors typically inform homebuyers when airgaps are not installed.

An airgap appears as a shiny chrome cylinder, approximately 2½ inches high, located at the rear rim of the sink. It usually makes a gurgling sound when the dishwasher is draining. To prevent a recurrence of last week's unpleasant surprise, installation of an airgap is advised. However, a common misconception among some installers is the belief that a "high loop" drain hose or a check valve may be installed in lieu of an airgap. These alternative methods are not approved because they do not provide foolproof anti-backflow protection. If the person doing your repair suggests one of these alternatives, just insist on an airgap.

• To write to Barry Stone, visit him on the web at, or write AMG, 1776 Jami Lee Court, Suite 218, San Luis Obispo, CA 94301.

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