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Community and Q&A

Is thermal imaging accurate?

Willo2355 | Posted in General Questions on

Customer had a thermal imaging co come out .images showed temperature deference so around wall outlets and switches.He thinks it is because of bad insulation install around them . ????Isn’t there a building code not to pack or install too tightly ???

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  1. Dana1 | | #1

    The standards for installing insulation isn't spelled out in building codes, but there are standards for rating the quality of batt insulation.

    When code requires a minimum R value in a framed cavity, voids and compressions will violated that code in the areas affected. But installing insulation "too tightly" will usually RAISE the R-value in those areas, as long as the cavity is completely filled. Packing it tightly (up to some limits) gives it a higher R/inch, so as long as all available inches are filled, it's a net win.

    For instance, blown fiberglass insulation fills all voids/gaps and thus has no compressions, but can be installed at a number of densities. At 1lb per cubic foot density most modern blown fiberglass comes in at about R3.7/inc, but at 1.8lbs density (packing it nearly twice as tight) it's usually about R4.3/ inch. Compare the R-value of this product at different installed densities:

    Voids & gaps and compressions where the insulation doesn't completely fill the volume are a far more likely installation error than packing too tightly (which is actually hard to do.)

  2. davidmeiland | | #2

    I do a lot of IR and could show you images of air leakage at outlets from virtually every house. Unless air paths into the walls are aggressively eliminated, they show up at outlets and a lot of other places, sometimes on exterior walls and also on interior walls in many cases. Fiber insulation has almost no effect on this although my belief is that dense-packed walls perform better than batted walls. Foamed walls usually but not always look a lot better.

    You could also be seeing the fact that batt insulation is rarely cut perfectly around electrical boxes or anything else, so there are usually air pockets around boxes that get cold and show up on the drywall with IR. There is also the fact that an electrical box is effectively a hole partway through the insulation. Depending on the size of the box and the depth of the wall, there can be very little insulation behind the box.

  3. DIYJester | | #3

    To answer your question, it depends.

    I deal with industrial clients that use $10,000 plus cameras for testing of various things such as furnaces,refractory, utility boilers, electrical equipment (breakers, connections, buckets, transformers, LTCs), mechanical equipment (bearings, paper machine siphon tubes). The biggest thing I've seen that causes poor images is not understanding emissivity and how objects can show radiation of energy of others.

    So in all, if done correctly, by someone who understands the equipment, its limitations, and truly how to use it; it is really accurate.

    I would say though you are probably dealing with a problem like the others have suggested unless you have a question about the images.

  4. GBA Editor
    Martin Holladay | | #4

    You've gotten some good answers here. To sum up:

    1. Thermal imaging is accurate, but adjusting a thermal imaging camera properly and interpreting the images on the screen is tricky. These skills require training. For more information on this issue, see An Introduction to Thermal Imaging.

    2. It is extremely common to see cold spots at electrical outlets on exterior walls during the winter. These cold spots are usually caused by two problems: (a) the lack of an effective air barrier, and (b) sloppy insulation installation practices or the use of a low-quality insulation product like fiberglass batts. For more information on these two issues, see:

    Questions and Answers About Air Barriers

    Installing Fiberglass Right

  5. johndoe2015 | | #5

    I usually use Daptex latex foam and shoot it all around the outlet behind and around it to help deal with the fiberglass airgaps. The latex foam is opencell and not as good as closed cell but its easy to trim/clean up around the electric boxes with water and towels.

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