Continuing my bad insulation smell saga, I've been exploring the room in question with a thermal camera. I have attached an example image that shows a cold spot in the wall (rest of wall is ~20°C).

Is there a simple way to determine if this spot is due to poor/missing/damaged insulation, or wet insulation? I suspect the answer is "drill a hole and look," but maybe someone more experienced than me has a trick.

enter image description here

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    If it wet enough the wall might feel spongy/soft at that spot, would still need to open to find the cause. If water pipe behind there, opening it up sooner is important to make sure of no leaks. If no pipes behind, it becomes more of when you have the time job. Have you seen the movie The money pit?
    – crip659
    Apr 1, 2022 at 11:49
  • @crip659 I have not seen the money, but I am indeed living in a money pit. This is an exterior wall with no pipes anywhere near. The drywall shows no sign of wetness.
    – negacao
    Apr 1, 2022 at 12:07
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    @SolarMike, you're right, I was hoping for an easy way out. But the last time I drilled a hole and looked, it was full of mouse shit and is going to be really expensive to deal with. I need a nice sandy beach to bury my head in. :)
    – negacao
    Apr 1, 2022 at 13:42
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    what is on the outside of the house in that spot?
    – jsotola
    Apr 1, 2022 at 22:36
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    Having dealt with wet walls myself, I can only say you reach a point of TINA - "There Is No Alternative" - you have to make a hole and take a look. Apr 3, 2022 at 3:21

1 Answer 1


It appears to me that insulation is missing in that spot, I have no idea why. The only way to be sure is look, using your suggestion to drill a hole and possibly place a small camera in. The fiber optic borescope are available for very little money. If possible drill the hole behind a picture or something hanging on the wall, that will help conceal it until you resolve your problem. If there is nothing there think of something to hang there to hide the hole until you fill and paint it.

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