hvac/r-value question

Ok folks, just got my camera and I am getting going on the infrared inspections. I am certified level I, but felt the majority of the course was beyond what info I need as a HI. Can anyone give me a little advice on scanning hvac systems and compressors, what to look for where to be looking, and any info on the likes. Also can anyone tell me a sure fire way to calculate r-value in walls? I have the flir sd which has the alarm, but as far as I can tell it cant exactly help calculate r- values. I feel like I should have taken the $500 nachi infrared course, it seems more appropriate. Thanks for all your help, Tim


Glad to see you posting!

May I suggest you subscribe to http://www.irinfo.org:80/tip_of_week.html and the many other IR site available.

I believe you’re R-value expectations are beyond any IR camera that I’m aware of. About all you can do with IR is evaluate for presence or absence of insulation in walls ,ceilings, floors and air or moisture intrusion at these locations. Beyond that you may be able to identify other mechanical anomalies but not R-value calculations.


Hey Tim who’s course did you take to get your Level-1 ??? did you take building science Level-1
Barry is correct on his statement Tim. If you set your emissivity on 96 for the indoor of the home you will get a proper reading when you use your camera. That’s what I have mine set at and it shows a clear visual of what to look for. Aslo make sure your distance from the wall is accurate. Check to see what your pixel size is for your camera which make a difference also. My camera pixel resolution is only 120x120 which is nothing compared to other nice camera I saw in class. The flir bcam-sd is made for more close up shots, this is what I was told by FLIR Mfg. Call and ask lots of questions, they will help you with any questions that you may have

NO dumb answer should go unanswered. All the guys here have helped me out also.

Good luck

Actually, your emissivity setting should be set to 1.00 when conducting a “qualitative” survey.

Good luck :slight_smile:



Don’t confuse him now.:wink:

Well guys, thanks for all the feed back. I was under the assumption with the ir camera I might possibly be able to get an idea of the r-value with a formula measuring inside temp vs outside tem and a few other factors thrown in,oh well. I will check out all the websites , and I have been researching as much info on line as I can. Thanks again for the feed back, Tim

Looks like another Lvl I vs. BS course issue.

I have written an Excel Spread sheet based on two graphs to approximate r-value.

What are you trying to use this for?


Because emissivity affects temperature value…not the image. The emittance tables provided by camera manufactures are “average” values taken in laboratory environments. They DO NOT take into consideration viewing angle, target shape, surface condition, or surface temperature.

Now, emittance is a critical consideration when dealing with “quantitative” themography or “acurate” temperature measurement. A thermographer can deal with emittance by using default values, emittance tables, estimation, or modification of surface. But, the “best” choice for dealing with emittance is to “measure” the emittance value (Level II Theory).

Just remember that “emittance” is not a static value. If you are not taking temperature measurements, just leave it to 1.00.


Kevin if looking at just thermal patterns as most Hi’s do I have not been able to tell the difference between 0.95 and 1 so I keep mine set on 0.95.

I was in class with a bunch of line electricians and they tried to pin the instructor down as to what was a specific E value for their work. The instructor would not commit kept bring out the crumpled aluminum and just smiled…

My Level 11 book arrived UPS today from Flir hope to have it read a couple of times before class starts, looking forward to it.

Hopefully after reading your Level II book and attending the class, you will understand why it is considered “best practices” to just leave the E value at 1.00.

You will also learn what the crumpled aluminum is for and how it is properly used. Every thermographer who needs to take “acurate” temperature measurements should have one.

Good luck with your Level II :slight_smile: If the FLIR class is anything like the one I took at Infraspection, you will have a lot of fun. Bring your thinking cap…it can be challenging at times.


OK, as I thought. What you were saying at my bed time was not clear.

There is no reason to set E to 1 if you are ignoring the temp measurement (I take these values out of the scan completely when doing qualitative work).
It (as you said) has no effect on the scan, only the temp reading on the screen. This reading is not a locked value when you snap the pic. You can change it on your computer (or in high end cameras) to anything. It has no effect on the scan, only the reading on the screen. Internally, your camera is recording an “Apparent Temp” of 1 and then doing the math to adjust the output numbers on the screen anyway.

You must set the E to 1 when determining emissivity (and when using the R-Value program we were discussing) because these numbers are needed for accurate mathematical computation.

I personally do not agree with setting the camera E to 1 as the majority of building materials are closer to the 95%E than 100%. In the event that you are looking at the “apparent temperature” between two objects in a qualitative instance to determine “relevance” (one circuit breaker versus another overloaded one) the delta T is closer to accurate. If you have a 10 degree delta at .95 it will be 5% higher (greater split towards error) at 1.0.

Though you should not be using the temp in quantitative scans, you can’t help it when you you are trying to justify to yourself that the anomaly is significant.

To adjust for reflect. Another setting that can be changed “later”.

Hey David, that was the deal, I spoke lots of people, most of ITC and flir and the majority recommended to take the level I. When all was said and done I gave them my input and I got an E mail from the hire ups offering me the BS course stating it was the one I should have taken. I just think these manufacturers and educational facilities need to take a bit more responsibility in training per field, They spend lots and lots of money marketing to HI’s, they should be responsible for teaching for our field. Just my feelings. The r-value reading is not cruciall at all, Just lots of curious clients, thats all. Thanks again, Tim

The laws of physics state that in theory only a perfect blackbody can have an emittance value of 1.00. Since there are no perfect blackbodies in the real world, the “best practices” method of eleminating “emittance” from a qualitative survey is by setting the camera to 1.00.

You don’t have to agree :slight_smile:

As far as your example above, I believe you are incorrect.

You have it “backwards.” If you lower the emittance, the Delta-T will “increase”

Here is a good document for you to read: https://secure.infraspection.com/comersus/store/comersus_viewItem.asp?idProduct=4125


This is why InterNACHI designed an infrared certified course for home inspectors.
But everyone has to find out on their own. Sometimes we have to pay a lot of money
and time to see the light.

Another well known infrared training school saw our course, and has now followed
our lead and is offering the same type of course and hours as InterNACHI infrared course.
They have started using InterNACHI’s Infrared Certified Trademark and logo also.
I applaud their actions. We need courses for home inspectors.

Good luck and call me if I can help. 936-546-2435

The E setting for home inspections works well from .80+ to 1 according to the
FLIR - ITC instructor who is over the BS course. I have that in writing. Since
it does not change the image, I see no debate for home inspectors who are only
comparing patterns for the most part.

Yes, sorry!
I was late getting out the door for work this morning. Got ahead (back wards) of myself! :slight_smile:

Now that doesn’t sound right after it re-read it! By higher, I meant to say the error factor is higher not the delta T.

My intention was to explain that most building materials are in the .95 range and below.

When you use 1.0 you are more in error because (as john said) there is no real 1.0 black body anywhere.

It is more likely that an object will be at (or closer to) .95 or below in Home Inspection.
When you set the camera at 1.0 you are moving away from accuracy at a greater degree. Plus or minus doesn’t matter, it is “more wrong”!
Why should I set my camera to 1.0, a setting further away from the known emissivity of all materials in the inspection?

I think the best practice is to remove it completely in quantitative work (as I posted).

Why, except to perform emissivity and T Reflect adjustment would I want an error factor increased by using 1.0 on an object with a .86 (or such)emissivity?

Thanks Kevin, I have it.

Also, good chart in the other link. I would post it but I don’t want to loose all this.

First, I think you are getting mixed up with your definitions of “qualitative” vs “quantitative” thermography.

Second, your assumption that if you set your camera to a default E value of 1.00 you are “more in error” does not make sense and is not accurate.

Lastly, I’m tired so I don’t want to debate with you. Agree to disagree :slight_smile:


Yea, I had a tough day today as well.

Beyond keeping things straight! :wink:

Chat with you next week, I’m on vacation upon completion of this report.

Before I go…

Lets draw pictures.

We have a scan of unfinished sheetrock with an emissivity of .93, Temp 86.6

Charlie B keeps his camera at .95, Temp 86.2

Kevin uses 1.0, Temp 85.4

86.6 - 86.2 = .4

86.6 - 85.4 = 1.2

I see this as “more in error”.
The camera did the calculations. Is it accurate?
Can you help me make sense of this? Why should Charlie and I change settings to get a measurement three time less accurate?
Is 1.2 degrees F significant? I guess that depends if you are taking direct or indirect readings.

I set my emissivity at .96.

I see no reason why any HI should set their camera at 1.0. If your performing qualitative and quantitative applications, that’s fine, but the average HI should be setting their emissivity at .96 in order to obtain close to perfect images and apparent temperatures.


I’ll try my best to explain it :slight_smile: Let’s start with a few definitions that I think need to be made very clear because you are again mixing them up.

Qualitative: art and science of detecting, displaying and recording the *thermal patterns *across the surface of an object

Quantitative: art and science of detecting, displaying and recording the thermal patterns and temperatures across the surface of an object

With that being said, I don’t care about the temperature of the sheetrock in your example above. What matters is the “thermal patterns” associtaed with the surface of the sheetrock. In your example I assume that we are looking at missing or mis-applied insulation behind the sheetrock. The temperature of the surface is irrelavent!

How do you know the emissivty of the sheetrock? Did you obtain that .93 value from a table? If so, you could be “very” wrong is taking “accurate” temperature measurements. This gets into “quantitative” thermography and that is where your seem to be getting mixed up. One of the worst things you can do is take a emissivity value from a table in order to measure temperate accurately. These tables are “average” values taken in laboratory environments. They DO NOT take into consideration viewing angle, target shape, or surface condition. The “best” method of accurately measuring the temperature of the sheetrock is to “measure” the emissivity.

Therefore, your whole example could be as you put it “more wrong.”

NO, NO, NO!!!

The camera is going to calulate the settings we put into it. It will LIE to YOU! Especially if the thermographer does not take the proper steps to “accurately” measure temperature.

I’m trying, but I think you are stuck on the “temperature” part of it.

It is NOT three times less accurate. Again, the temperature is NOT rellavent! Furthermore, the whole example is not “accurate” because you did not take the proper steps to measure for E,R & T.

Hope this helps :slight_smile: