How to Tell If Walls Are Insulated

Home insulation
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  • 01 of 05

    Checking Walls for Insulation Without Removing Drywall

    Fiberglass Insulation in Walls
    Hans-Peter Widera/Getty Images

    If your house is too cold or too hot, despite the furnace or air conditioner constantly running, you may begin to wonder what's going on. As long as you have effective windows, good weatherstripping, and attic insulation, your house should stay reasonably warm or cold. The next logical thought might be: Do I even have insulation in the walls? Unless you bought the house new, built it yourself, or remodeled it yourself, this can be a vexing question.

    Attic insulation, by contrast, is easy to check on. Simply find the attic access panel (usually located in a closet), set up a ladder, and pop your head in the attic. You will instantly know whether or not you have insulation. Walls are a different matter. 

    Two common methods do not yield definitive answers: touching the wall and knocking on the wall. An uninsulated wall will feel chilly to the touch only when there is a significant difference between interior and exterior temperatures. Also, you need to have another insulated wall in the house to touch, by way of comparison. Knocking on the wall is even less reliable. Unless you are highly experienced at this, insulated walls often sound as hollow as uninsulated walls.

    Short of entirely gutting the walls and removing all drywall, there are a number of methods that will let you know if your walls have insulation. Most of these methods are invasive, but only slightly so. In some cases, the small holes will be covered up with another material. Or the hole will be in a visible area but it can be patched easily. In some cases, no hole needs to be created since you will be using existing holes.

    Tools and Materials You May Need

    Not all of the following tools will be necessary. Use only the tools that you need.

    • 3/4-inch hole saw
    • Flat pry bar
    • Brad gun or cordless nailer
    • Inspection scope
    • Stud finder
    • Hammer
    • Cordless drill with a driver bit
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  • 02 of 05

    Remove Electrical Box and Check Wall

    Electrical Box
    Lee Wallender

    Cutting a sizable hole in the drywall is one of the best methods for determining whether or not your walls have insulation. Your walls already have many holes in the form of cutouts that accommodate electrical boxes for light switches and outlets. In some cases, you can remove the faceplate with a cordless screwdriver and see fiberglass insulation packed so tightly in the walls that it pushes through slits around the box.

    Old-work or remodel boxes can be removed entirely since these boxes are not attached to the studs.

    1. The circuit that runs to the box should be shut off.
    2. Remove the wires from the device, taking note of their positions.
    3. Once the box is free of the wall, slip the cables out of the back. Make sure that they do not fall back into the wall.
    4. Now you can check in the wall for insulation.
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  • 03 of 05

    Check Under the Baseboard for Insulation

    Drywall will often have space at the bottom as a normal part of the installation. You might be able to see fiberglass insulation or, more likely, the paper facing of fiberglass insulation. 

    1. Gently insert your pry bar behind the shoe molding or baseboard (the trim that runs along the bottom of the wall). To prevent damage to the wall, put a piece of thin board behind the pry bar.
    2. Pry back the baseboard. These moldings are usually secured only by brads and are easy to remove. Use your pliers and pull straight back to remove any wayward brads protruding from the wall.
    3. If you do have fiberglass, the paper backing might push out of the bottom since it needs to be stapled to the bottom-most stud. Blown-in insulation might be visible through this slit, as well.
    4. Re-install the baseboard.
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  • 04 of 05

    Cut Hole Through Area Covered by the Baseboard

    If insulation is not visible through the bottom of the drywall, try to cut a small hole about 1-inch above the floor. This hole will rise above the bottom-most stud but will still be lower than the top of the baseboard.

    1. Using a stud finder, locate a space between two studs.
    2. Mark a light line along the top of the baseboard.
    3. Remove the baseboard.
    4. Cut a 3/4-inch hole in the drywall near the floor but still below the level of the line that you marked.
    5. Insulation that runs the entire length of the wall cavity will get caught in the drill. A reasonable conclusion is that the entire wall has insulation.
    6. If you see no insulation and you have an inspection scope, run it into the wall and look upward for insulation. A wire clothes hanger with a hook formed on the end also allows you to probe around. When you pull out the hanger, it should have some insulation attached to it.
    7. Install the baseboard again.
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  • 05 of 05

    Cut Hole Above Kitchen Cabinets or in Closet

    Instead of checking low areas for insulation, another option is to check high areas that are not visible.

    1. Locate a high area that is fairly unobtrusive. In kitchens, this will be above the cabinets. In bedrooms, this will be inside of closets.
    2. Cut a 3/4-inch hole in the drywall over the kitchen cabinets: the lower, the better. Do not cut so low as to affect the cabinets. As with other methods, you first want to locate studs so that you do not inadvertently try to cut into a stud. Keep the drywall plug. You will reuse this when later fixing the hole in the drywall.
    3. Run the inspection scope or wire down. Because blown-in insulation can settle and leave a space at top, it is important to check several feet down. With the wire hanger method, you can quite clearly hear the hanger tapping both ​sides of the wall. With the inspection scope, it is visually obvious.