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What is the best way to determine existing insulation?

user-1140356 | Posted in General Questions on

In an existing home, what is the best way to determine existing insulation in the finished walls. It is known that the walls have unequal insulation due to renovations and additions to the house. That is, different areas of the house (and different areas of the same wall section) have different insulation. Some areas have 1 inch foam with 3.5 inches fiberglass. Some areas have cut and cobble foam insulation. Knee walls may have fiberglass that is sagging. Aside from buying an expensive thermal imaging camera, how can I tell what is in the walls, ceilings and knee spaces. Should I cut holes in the drywall? Can I poke a drill bit in and discover what is in there?

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  1. GBA Editor
    Martin Holladay | | #1

    A thermal imaging camera is certainly a useful tool to help you answer this question. For more information on thermal imaging, see An Introduction to Thermal Imaging.

    If you can't afford to hire an energy auditor to scan you home with a thermal imaging camera, you have to do your own detective work.

    (1) You can turn off the relevant circuit breakers and inspect insulation near electrical outlets. Remove the cover plate, and slightly widen the drywall opening. Use wooden chopsticks or similar tools to snag some insulation; if the crack is wide enough, inspect the crack with a flashlight. Then caulk the crack and replace the cover plate -- if necessary, with an oversized cover plate.

    (2) You can make inspection holes in the drywall. The best places for these holes are closet walls and locations behind large pieces of furniture. If no one in your house cares what the drywall looks like behind the furniture, your drywall patch can be fairly crude. Otherwise, get out the mud bucket, sanding screen, and paint.

    (3) You can remove a few courses of vinyl siding (if that's what you have) and drill a few holes in the sheathing from the outside of your house. Vinyl siding is easy to remove and re-install. Don't forget to patch the housewrap when you are putting everything back together.

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