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Inspecting Home Closed Cavities

To complete the inspection, you'll need a flashlight, a screwdriver, tape measure, and pencil and paper. You may need a drill and small bit for drilling drywall. You'll need some type of thin probe that doesn't conduct electricity and can slip past a plumbing drain or electrical box and into the wall cavity. The ideal tool is a pointed bamboo skewer like those used for grilling teriyaki. Do NOT use a piece of wire if you expect to probe around electrical boxes, identify the proper circuit and shut the power off at the electrical panel. Stop now if you are not comfortable working around electrical equipment.

  • To inspect wall insulation, look first for an opening around plumbing or electrical penetrations. Look under your kitchen or bathroom sink, if they are on exterior walls, to see if there is a space around a drain line that goes through the wall. Try in the laundry room, where the washer or dryer pipes and vents may pass through exterior walls. You can also use a drill to cut a small hole (0.5 to 1 inch in diameter) through the drywall in an inconspicuous place. This is the method usually chosen by professionals. The ideal location is at the back of a closet in an exterior wall and near the floor, or in the wall under the kitchen sink. Avoid drilling into studs, and be careful not to cut any wires or pipes.
  • Once you have created an access hole, peer into the cavity with your flashlight to see what type of insulation is installed. If you don't recognize it, take a sample so you can ask your expert at the home improvement store. Try to determine how thick it is, and don't assume the cavity is full. Push your wooden probe all the way to the outside of the wall, up against the exterior sheathing. You can often disern the thickness of the insulation, and the presence of any paper facing or plastic air barrier, as your probe penetrates the layers.
  • Measure and record the depth of the insulation, and of the wall cavity itself.
  • Walk around your home again, and determine if the cavity you inspected in characteristic of the wall framing throughout the structure. Have additions been added to the building? Is there a second story that has a different framing design? Perform additional inspections as needed.

With this information, you've reached a critical decision point. Are the closed cavities completely full of insulation? If you have found cavities that are empty or only partially full, you have an excellent opportunity to improve the thermal efficiency of your home.

If the cavities are full of insulation, then you'll need to direct your insulation improvement efforts elsewhere. You would benefit, for example, from adding exterior insulation, outside of the existing cavity, in conjunction with the installation of new siding and windows. That large retrofit is one of our primary recommendations for homeowners who are committed to creating the ultimate in efficient homes.

Home Efficiency Tips