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IR pitfalls


Chris Bernhardt
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There's lots of non-specific warnings out there with respect to using IR in a home inspection. I'll start with a few easy pitfalls, and I hope others will join in and add to it or tell stories.

Tip 1: Be careful when your camera is set to autorange. I'll usually start out with it on autorange, but autorange can make an anomaly with insignificant temp differerential look like some big deal. When you find a curious anomally, take the camera off autorange, and read the indicated temps on and around the anomally. Often times, what appeared to be some big time anomally has no significant temp differential.

Tip 2: Always, always, always verify the anomaly. To do that in normal HI work, you'll need more than one moisture meter. The GE Surveymaster isn't sensitive enough to detect water pooling on the back of ceiling drywall. You'll need a Tramex ME+ or someother brand that sensitive.

Tip 3: When you start out, I recommend that you have a GE Surveymaster and a Tramex ME+ and if can swing one, a Tramex Wet Wall Detector. Every anomaly that you are curious about, scan it with the Tramex and the SM and then probe it with the SM in pin mode. I don't know how you can make a verification of an IR anomaly without carefully scanning it and sometimes even probing it with your moisture meters. When I find a bona fide leak, I'll make more effort to study how the camera correlates with what the moisture meters say and what my eyes say, etc.

Tip 4: Conduct your own experiments. Get a piece of drywall, siding products and other building materials and even make up mock assemblies and simulate leaks and scan with your IR cam and moisture meters etc.. If doing this doesn't make you an expert, I don't know what will.

Tip 5: At least for me, my IR cam is an order of magnitude more useful in the rainy season then in the summer. In the summer, I'm mostly catching leaky 2nd story plumbing fixtures.

Tip 6: Be aware that your moisture meter may be pegging on the damp swollen floor around the toilet and the IR cam sees nothing. For those times when there's no heat flux, experiment with a heater to create some flux and then get a cool image of the outline of all the moisture damage. I use a hand held hair blower. I would like to know what others have found useful for inducing a flux quickly.

Tip 7: Play around with the palettes. Now, I haven't found that one palette is necessarily better than another for this thing or that thing. If anyone has, please let us know. Changing palettes can sometimes be useful at indicating the difference between moisture and insulation anomalies in the ceiling assembly before you have time to go and drag in your ladder, to go up and scan it with your moisture meters.

Tip 8: Use your IR camera. Don't leave it in the case. Make it a point in every inspection to do a quick scan and try and learn something.

That's all I have time for, for now. I hope others will add to this.

Chris, Oregon

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That's pretty good stuff, especially #1 and #2.

I'm in the experimental stage, and have set up various situations similar to what Chris described. It's a tricky thing to understand, and practice is key.

Yes, it's fairly useless for envelope work unless there's been heavy rains.

What's really amazed me is how many times I find leaks after a heavy rain.

I haven't owned it during a heating season yet; I'm looking forward to finding insulation issues.

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My use of IR so far has been primarily to find plumbing and roof leaks. I don't get worked up with the insulation anomalies, as there's always some in my neck of the woods. However, the IR camera is great for finding the missing insulation in vaulted ceilings in new construction.

I also haven't gotten in to looking at the electrical system with IR. I was hoping that Jim Katen has or will and can give us some pointers.

Chris, Oregon

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Yeah, the insulation thing isn't all that exciting, and there's always missing or inadequate insulation in Chicago.

With the electrical, I haven't found much of anything. There's always a breaker or two that are a few degrees warmer than other breakers, but that's about it.

The AFCI's are always several degrees warmer than other breakers.

That's about it, but I'm not stopping trying to find stuff.

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I've been told looking at IR in gray scale is the best way to look for anomalies, and the rainbow and iron colors are mainly for show. I typically scan in the rainbow mode and will switch to gray scale once I find an anomaly. I’ll admit the anomaly in gray scale is easier to interpret because there’s a lot less to distract you.

One question I’ve been meaning to find the answer too is, how hot is too hot for an electrical breaker? Like Kurt said AFCI and 220 volt breakers under load are typically a higher temperature, most around 90-100 degrees depending on ambient temperature which seems to be normal. I would imagine the only true way to know is the same size breaker under the same load and comparing the two. I would like to know what temperatures the breakers are that ya’ll are scanning though. Also when scanning electrical panels do ya’ll scan the breakers under a load? Such as, running the heating and air etc?

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Anomalies are relative. There's no particular range and span to find stuff that I know in normal HI work. Like I said, I run around with the IR camera set on autorange and then only take it off autorange when I find an anomaly that I want to analyze further.

Grayscale can sometimes give you better contrast, but I prefer to use the iron palette on my IR camera. In other words, I normally run around with it on the iron palette, then I might switch through several other palettes when I'm studying an anomaly.

I can set alarms on my camera, which I have found marginally useful sometimes when I'm looking for potential condensation points in the winter.

The thing to understand is that the IR representation is highly relative; don't think of it as absolute in HI work. You are not going to be standing there trying to analyze the image. You don't have the time, at least I don't and my camera doesn't have that level of resolution anyway. Instead I scan fairly quickly around to find anything interesting. Then my process of analyzing an anomaly includes:

  • Look at the thing without using the camera by using your eyeballs. Try and glean any possible clue that you can use in future work.
  • Consider the assembly and materials of what you are looking at. Understand the limitations of how moisture or the defects you are looking for are typically represented. To know this stuff takes a deeper consideration as to the science of it all, perhaps this is what the non-specified warnings are based on, I don't know.
  • Use any of the other tools at your disposal to characterize the anomaly. For example, with drywall I usually start with the Tramex (high sensitive scanning moisture meter), then if it indicates something, I switch to my GE Aquant (less sensitve scanning moisture meter), and if that indicates something, maybe switch to a protimeter (pin type meter moisture meter).
  • I might try and charge part of the anomaly with my hand or another heat source, then stand back and use the IR camera to watch how the results decay/fade; moist/damp/wet assemblies have more thermal capacitance.

One particular scary thing is that perfectly looking roofs may actually be leaking. If they are, I can usually find them during the rainy season with IR even though my eyeballs can't. But, during the summer, I can't know for sure if the that roof leaks or not. What I realized in my second year is that the envelopes of a building leak. They all leak. The concern is whether the leaking is problematic or not. Any one assembly can handle a certain moisture load, but understand this that the variables are huge. In other words, you can't go to school or take a class to teach you rules that will guarantee results. And again, maybe this highly relativeness of using IR is the basis of the non-specific warnings.

I think the problem is some folks come at the HI thing thinking that all they have to do is learn a large set of absolutes, and then they can kick back and be successful. That's what I love about this biz, it's full of relativities, and that seems to drive some folks crazy.

Chris, Oregon

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Tip 9: Don't make the mistake of expecting to find all important anomalies just by scanning with your IR camera. Always, always, always, include a careful scan with your eyeballs and a powerful flashlight. Some of my most important finds, I missed on my initial IR scan. The reasons:

  • Either I was too far away and the anomaly was relatively small for the resolution of my camera
  • The camera autoranged at an inopportune moment due to heat source like a light fixture, heat register, or just about anything, which obliterated the anomaly.
  • The anomaly has come to equalize with room temp and won't show up until you step the temp in the room

Tip 10: You don't always need the big temp diff you've heard about. I suppose if I was doing whole home IR evaluations, I would make more of an effort to get them, but in performing just a regular home inspection, I make no attempt to create them. Just stepping the temp by a degree or two by turning on the heating system can create dramatic results in the winter; think thermal capacitance.

Tip 11: Best time for looking at the exterior is shortly after nightfall on a windless night.

Tip 12: When trying to find 2nd story plumbing leaks, always scan the ceiling first carefully noting the presence of any anomalies even scanning them with your moisture meters, then go and run water, then later rescan the ceiling for changes both IR and verify with the moisture meters. Plumbing near the surface of the drywall can induce an anomaly in the ceiling assembly and if it's near enough, you'll even pick up the capacitance of the pipe or even the water in a trap with a moisture meter. In other words after the piping cools or heats, an anomaly is induced, but because you already had scanned suspected areas with your moisture meter and the fact that the moisture meter is indicating no significant change means it's probably not a leak. In some cases, you might not initially know where the piping is. As you run water, scan the ceiling with IR and take a moisture meter reading to establish a basis upon any anomally you see developing. Later at the end of your test, you can then rescan the anomalies for any significant changes from the initial basis that the moisture meter indicated.

Tip 13: Other uses - After I have been running water in plumbing fixtures for a little while, I'll check visually for leaks, but as many of you know leaks might not show up right away, so at the end of the inspection I might go back and scan around the toilets and in sink cabinets with the IR camera quickly. I have on some occasions found leaks that had escaped detection of my eyeballs.

Chris, Oregon

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I would like to know what others have found useful for inducing a flux quickly.

A halogen work lamp on a stand can be quite useful for this. Point it at a suspected surface for a while, then turn it off and look with the camera. The main thing I use is a 4000W electric heater. Close the doors to a room with the heater inside and the temp usually goes up several degrees in half an hour or so.

Best time for looking at the exterior is shortly after nightfall on a windless night

I like to go right after dawn, when it has been cold all night and the house is heated.

The camera autoranged at an inopportune moment due to heat source like a light fixture, heat register, or just about anything, which obliterated the anomaly

If I am looking at walls, I set the camera to a narrow span, anywhere from 6-10 degrees, and keep it there. Going back and forth fairly often between manual and auto is usually necessary.

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Yes, I've found it necessary to switch back and forth between auto and manual; on occasion, some incident will mess up the read on auto.

I've found that just after sundown or right @ dawn is the best time for looking @ building envelopes.

How many flat roofs have you guys done?

I'm not finding it particularly helpful on flat roofing issues. I do flat roofing right after sundown, and honestly, I don't think I've ever found a problem with roofing with the IR.

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Either sundown or dawn will work. I haven't experimented doing both. I wonder if one is more useful then the other depending on whether it's winter or summer.

It appeared that the flat roof guys were picking some time in the middle of the night that was creating the best temp diff. I haven't gotten into looking at flat roofs. I'm imagining that theres lots of thermal capacitance that they get to rely on, so they pick the coldest time of the night or morning to check the roof.

Thanks David for sharing your heat source tip.

Chris, Oregon

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I would suspect sunset to be a terrible time to scan a flat roof. After cooking all day the temps will be so consistent that you'd need a hole big enough to put your foot through to see it, even with Kurt's hi rez camera. I would think that early morning would yield better results. My experience is that differentials of only a few degrees are far easier to see (in any palette) when temps are cooler, 70's and 80's rather than 100+.

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The proposed theory of *just after sundown* is like the other stuff; you're betting the transition of the heated roof to the cooling roof is going to show you the temperature difference of the water film under the membrane. I read and heard this technique proposed on several occasions. Of course, like all of it, timing is the key. You can't just go up and shoot and leave; you have to hang around for a while, take a lot of shots, and get lucky, basically.

I've found anomalies, but honestly, I could find the leaks without the IR. Roofing isn't that complicated.

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I've read comments from several flat roof IR guys and the timeframe seems to be at least a few hours after sundown, when the day was warm and sunny and the night is clear. They go up in the dark, hopefully with someone to help keep them safe, since walking around looking at the screen will make you blind when you try to see where you're placing your feet.

Of course, if you're really cool you just do an aerial survey and never even land in the state where the building is located. http://www.aitscan.com/roofmoisturefindir.php

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  • 4 weeks later...
  • 3 months later...

I'm a new memeber buying a thermal imager this week, looking forward to participating with and learning from you all. As to the questions about using IR to scan electrical panels, I am an electrician by trade and have been to some thermography seminars where this came up. i plan to use mine for electrical PM in an industrial setting. First anomalies are just that, different and unexplained, 30 degrees F in difference from the hot breaker to all the rest is a major problem, ten is normal variation, Scale adjustments need to be made for checking this, 20 can be load but merits checking into, first the tighteness or torque on the screw that holds the wire into the breaker most THLQ or HACR residential type 20 amp breakers with 12 ga wire require 25 inch pounds of torque, if you check your own panel under load then torque all of the breakers (while turned off) then re-scan a while later you will probably observe a big reduction in heat, resistance= heat! I picked up a nice torque driver at Harbor Freight for ten bucks adjustable from 5-50 IN/lbs. What's really important is that 240 appliances like the range or condenser are balanced or are at the same temp by 3 degrees between legs. (note some new appliances like high efficiencey dryers run two separate 120 legs and this will not apply to them) It helps to use a clamp meter to check that the amperage under load does not exceed the breakers rating or that of the wire guage 20 amps for 12ga etc. I have used Thermal imaging to find hot wires then used a clamp meter to find out that there were 30+ amps going through the wire because the breaker was siezed and the circuit was overloaded. Pay special attention to this condition with regards to the bridge tabs on the sides of wall outlets! I watched the wall catch on fire at a friends house right in front of me while I was drinking a cup of coffee, the paint started bubbling! Outlets should not be installed with four conductors, but rather two with nutted conections in the back of the box. Good luck!

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