My new toy - IR Thermometer


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Old 01-03-16, 07:15 AM
P
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My new toy - IR Thermometer

I bought myself a Milwaukee Laser temp gun, model 2266-20 and started to test all my improvements (extra insulation on the attic, closing off recessed lights etc....)

I must say that I am bit confused about the readings.... and so I wonder...how many of you pros are using such tools, as it seems to me they are not that accurate.

For example; how do you explain that pointing at a wall with brand new R19 I am at the same temp. reading as when I point at another part of the same wall that I know has very old R11 insulation?

Just looking for general feedback on these tools and what to really expect of them.

thanks!
 
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Old 01-03-16, 08:18 AM
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Hi Paul,
There may only be a couple of degrees difference between the surface temperature of an r-11 and an r-19 wall. That surface temp does not directly tell you how much heat is passing through. This link looks good although I have not read it specifically, many others.
https://www.ag.ndsu.edu/pubs/ageng/structu/ae1373.pdf

In addition, IR Thermometers have a target area and that area can include wall studs which would average into the temp reading with a lower number.

Years back I borrowed and used one and like it, but they do take some getting used to. In my work I use an infrared camera to get the whole picture and they are immensely powerful tools, and you can rent them now.

Be sure to account for the reflectivity of any surfaces you test.

Bud
 
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Old 01-03-16, 08:42 AM
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IR thermometers are good gadgets and can be a useful tool but you do need to know how to interpret the results. First you have to understand that it's seeing light. Not light we can see but it's light none the less so it can be reflected and affected by the surface it's coming from. So, using an IR thermometer on shiny metal surfaces can yield some really odd results.

Next is the viewing area. It's basically a lens on the front so it looks out in a cone. Even if you have a laser dot for aiming the area the sensor sees is actually a cone fanning out in front of the device. Some fan more than others but you can quickly be up to a saucer sized viewing area. Then you have to guess if it's seeing an average of the area or if one item is emitting (shining brighter) than the others and dominating the reading.

For serious fun beg, borrow, steal or rent a IR camera. They are extremely good at pointing out insulating problems. But any device will have trouble sensing an insulation problem if the temperature outside is nearish the inside temp. So, the cold of winter is best. Cold spots and studs stand out very obviously. In the fall and like this winter when we've had very mild temperatures insulation problems can be difficult to spot inside. But an IR camera can easily spot the difference between different R values. With an IR thermometer you need really cold temps outside and some skill/experience.
 
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Old 01-04-16, 07:00 AM
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Paul, I'm not a pro but have used an IR gun with much success so I'll offer my thoughts. Unless you're doing this for some scientific purpose I wouldn't be so concerned about absolute numbers as much as variances and trends. Look for places where the reading changes and try to interpret that change to see what you can do. Keep in mind that you want to stop cold from getting in and heat from getting out.

I'd say you're doing it right: going into the attic and look for hot spots as an indication of where insulation is needed - you'll probably also find gaps caused by plumbing, etc. Possibly go into the basement and do the opposite, looking for colder areas to caulk or seal. If you have hot air heat identify ducts / registers to seal. Lastly, go outside and do the same - seeking places where heat is escaping that you can caulk.

From a technique perspective, the further your gun is from the point you're aiming at the more other stuff will interfere with the reading. Thus, try to get as close as possible.
 

Last edited by Tony P.; 01-04-16 at 07:32 AM.
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Old 01-04-16, 10:25 AM
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Originally Posted by Tony P
I wouldn't be so concerned about absolute numbers as much as variances and trends
I agree with this statement.

Interpretation is key with these things - point the thermometer at a mirror & when you get a section of the mirror reading 80+ degrees, it'll help you understand one of the key principles on using one properly. Another thing - point this directly at a heat supply vent for a minute & then measure something. Let the thermometer "cool off" & measure that same thing a minute later & that second reading will be lower. Lots of things you gotta worry about as opposed to pointing & shooting but look for variation as opposed to the exact numbers. Just don't go comparing a reading of a shiny metal duct with that of drywall.

These things measure thermal radiation to deduce a temperature reading. Everything emits thermal radiation (ever seen those infrared police-helicopter videos & though you can see the suspect, you can still make out the outlines of buildings, trees, etc..)...so the closer you are, the better.

Regardless of the technology, saying a wall that has R11 is at the same temp as a wall that has R19 is a vague statement. Too many questions. Thermal equilibrium is always happening. The point of insulation is to impede (conductive) heat transfer. Like Bud says, a single temperature reading doesn't tell you anything about heat loss. Two objects with the different levels of insulation could be at the same temperature at t=0, different temperatures at t=5, and the same temperature at t=10 because equilibrium has been reached.
 
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Old 01-05-16, 04:31 AM
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thanks guys....thought it would be a different experience I guess...
 
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Old 01-05-16, 07:54 AM
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Don't let us ruin the party...have fun with it, learn what you can from it, just make sure you realize some of its intricacies before making decisions based on data you obtain from it.
 
 

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