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Measure Your Home Insulation

Measure Your Insulation

You'll want to inspect the insulation in your home. To assist in the inspection, you'll need a flashlight, a screwdriver, a tape measure, and pencil and paper. A ladder may also be required.

Start by walking around your home and identifying all the parts of the building that could have different insulation details. New additions, for example, often have a framing structure that allows more insulation than in the original building. Your home will have, at minimum, different insulation details at the walls, ceiling, and floor, and it could have several different details for each. Create a list to keep track of your findings.

  • Attics

    If your home has a pitched roof and an open attic, you'll need to find the hatch. It may be outdoors, in a hallway, or in a closet. If it is in a closet, you may find it troublesome to clear things out of the way to gain access, but this inspection is well worth your time:
    • If needed, find a ladder, set it up securely, climb up and open the hatch. You may be able to inspect the attic from the ladder, or you may need to climb all the way in. Bring a flashlight and tape measure. Wear a respirator. Step only on the framing so you don't damage the ceiling or hurt yourself. Stop now if you are not comfortable with the risk involved.
    • Inspect the insulation, and identify the type. Fiberglass batts are pink or yellow and come in rolls. Loose-fill fiberglass is white, pink, or yellow, and looks like chopped-up batts. Cellulose looks like, and is in fact made from, chopped-up newspapers. If you don't recodnize the type of insulation, take a sample to your local home improvement store and ask an experienced employee.
    • If you're evaluating batt insulation that came in rolls, it is probably marked with an R-value printed either on a paper or foil face, or on the batt itself. Note the R-value.
    • If you are evaluating loose-fill insulation, measure the thickness all the way down to the top of the ceiling surface. If it varies in depth, take an average of thicknesses. Calculate and record the R-value according to the procedure shown here.
  • Calculating R-Value

    Once you know the type and thickness of your insulation, you can calculate its R-value:
    • Identify the type of insulation. Determine the R-value per inch from the table below. Use the average R-value from the table.

      Building Material R-Value per Inch
      Concrete 0.1 or less
      Wood 1.0 to 1.5
      Fiberglass batts (standard) 3.0
      Fiberglass batts (high density) 4.0
      Fiberglass (loose-fill in open attic) 2.3
      Fiberglass (dense-pack in cavity) 4.0
      Cellulose (dense-pack in cavity 3.2
      Cellulose (loose-fill in open attic) 3.4
      Mineral wool batts 3.3
      Expanded polystyrene foam board (white beadboard) 4.1
      Extruded polystyrene foam baord (usually blue, yellow, or pink 5.0
      Polyurethane spray foam (low density) 3.7
      Polyurethane spray foam (high density) 6.5
      Polyisocyanurate foam board (foil-faced) 6.5
    • Measure the thickness in inches.
    • Multiply the R-value per inch times the number of inches.
    • Examples of R-Value Calculations
      3.5 inches fiberglass loose fill in atticAverage R-value of 2.3 per inch3.5 x 2.3 = R-8
      3.5 inches cellulose loose fill in atticAverage R-value of 3.4 per inch3.5 x 3.4 = R-12
      24 inches fiberglass loose fill in atticAverage R-value of 2.3 per inch24 x 2.3 = R-55
      3.5 inches fiberglass dense pack in wallAverage R-value of 4 per inch3.5 x 4 = R-14
  • Measuring Closed Cavities

    The most common cavities are within standard vertical walls. In North American frame homes, the typical wall is assembled from wooden two-by-fours (3.5 inches in actual thickness), or two-by-sixes (5.5 inches in actual thickness).

    Vaulted or cathedral ceilings have closed cavities above their ceilings instead of attics. These roof cavities vary in depth depending on the roof framing, but are usually 8 to 14 inches thick. Some homes are built with a combination of open and closed attic cavities.

    Closed cavities are also sometimes constructed over garages or above unheated basements. These floor vaults vary in thickness depending on the framing, but are usually 6 to 12 inches thick.

    The trick to inspecting vaults is in finding access to look inside. You may be tempted to skip this inspection on the assumption that the cavity was completely and correctly filled during construction. Our experience has shown this is rarely the case. Take a look at our suggestions on inspecting these areas of your home here.

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