Blog #064 – Your THERMOGRAPHY COMFORT LEVEL – Emissivity? What is it? Is it important?

Every target surface that you point your infrared camera at has a surface characteristic of emissivity.  How’s your comfort level with that subject?  I talked about this a little in blog #015 (Radiosity!  What is it?)  As you might remember, there are three components to radiosity: (1) emissivity (2) reflectivity (3) transmissivity.  All three have to equal one.  So, if the emissivity is 0.95 and the transmissivity is 0.00 the reflectivity is what?  Yes, 0.05.

How important is it to understand emissivity?  Well, how important is the accuracy of your temperature reading?  Your infrared camera, if it is a radiometric camera, gives you a surface temperature reading, right?   Let’s say your IR camera is in perfect calibration and the reading is minus 3° F.  Is that an accurate temperature?  Maybe!  Maybe not!  The target surface characteristic called “emissivity” has a major influence on it.   When you hear the word “emissivity”, what comes to mind?  The thing that comes to my mind is the word “emit”.  Target surfaces vary in the amount of infrared radiation that they “emit.  The higher the emissivity of the surface, the more infrared radiation it emits.  The more it emits the more accurate the temperature reading from you camera.  Please notice that I have emphasized the word “surface”.  Why?  Because an infrared camera reads only the infrared radiation that is emitted from the “surface”.  For example, on a painted wall the camera reads the infrared radiation emitted from the last coat of paint, not anything below that.  Polished chrome, for example has a very, very low emissivity of 0.05 (high reflectivity).  Paint has a very, very high emissivity of 0.95 (low reflectivity).  What, then, is the emissivity of painted chrome?  It’s the same as the emissivity of “paint” because that is what constitutes the surface.  Notice the same image I used in blog #015, the image of the car with a chrome surround on the windshield.

Taken with Fluke IR Fusion camera

Taken with Fluke IR Fusion camera

The ambient temperature is around 110° F.  The painted door panel is 144.1 ° F.  The polished chrome surface is reading -3° F.  The paint, due to the high emissivity of paint (.95), is giving us a relatively accurate temperature surface temperature of 144.1° F.  The polished chrome, with its very low emissivity  (.05), is giving us a very inaccurate temperature of minus 3° F. 

 A good question to ask yourself when pointing an infrared camera at a surface is: “What is the emissivity of this material?”  If you are involved in moisture investigations or building envelope investigations you are most often viewing high emissivity surfaces.  Be careful about aluminum HVAC surfaces, though.   If you are involved with industrial, manufacturing, mechanical investigations you will have to be more aware of the varying surface emissivities.  In the next blog I will address how you can change the emissivity of a surface to achieve accuracy.

 Call me any time for further discussions on these subjects.

How’s your comfort level in thermography?
(The above comments represent my opinion).

Rod Hoff / Restoration Consultants Inc
Thermography Instructor / IR camera sales
3284 Ramos Circle, Sacramento CA 95827
toll free 888-617-3266 ext 301
fax 916-736-1134
rhoff@restcon.com

Provider of Fluke TiS, TiR, TiR1, Ti, Ti25, TiR27, Ti27, TiR29, Ti29, TiR32, Ti32, TiR3, and TiR4 infrared cameras.

See DEMO www.moistureview.com/demo.html

Posted in building envelope, Fluke, general, infrared cameras, Thermography | Tagged , , , , , , , , , | Leave a comment

Blog #063 – Your THERMOGRAPHY COMFORT LEVEL – Exercise #4 – insulation detection!

Review Blog #060, #061 & #062 and continue with the exercise.

Cool wall cavity areas (darker color) and warmer wood framing (lighter color):

Scenario #7 – viewed from the outside during the cooling season (summer) – are the bays insulated?

Scenario #8 – viewed from the inside during the cooling season (summer) – are the bays insulated?

exercise cool bay scenario

exercise cool bay scenario

(Answers:)

Scenario #7 – no insulation

Scenario #8 – insulated

 The intent of these 8 scenarios in these four blogs (#060, #061, #062, #063) was to give you an opportunity to practice thinking on a molecular level.  Hopefully this has raised your thermography comfort level.

How’s your comfort level in thermography?
(The above comments represent my opinion).

Rod Hoff / Restoration Consultants Inc
Thermography Instructor / IR camera sales
3284 Ramos Circle, Sacramento CA 95827
toll free 888-617-3266 ext 301
fax 916-736-1134
rhoff@restcon.com

Provider of Fluke TiS, TiR, TiR1, Ti, Ti25, TiR27, Ti27, TiR29, Ti29, TiR32, Ti32, TiR3, and TiR4 infrared cameras.

See DEMO www.moistureview.com/demo.html

Posted in building envelope, Fluke, general, infrared cameras, Thermography | Tagged , , , , , , , | Leave a comment

Blog #062 – Your THERMOGRAPHY COMFORT LEVEL – Exercise #3 – insulation detection!

Review Blog #060 & #061 and continue with the exercise.

 

(Warm wall cavity areas (lighter color) and wood framing (darker color):

#5 scenario:  viewed from the outside during the cooling season (summer) – Are the bays insulated?

#6 scenario:  viewed from the inside during the cooling season (summer) – Are the bays insulated?

Exercise warm bay scenario

Exercise warm bay scenario

(Answers:)

Scenario #5 – insulated

Scenario #6 – no insulation

 Look for Scenario #7 and #8 in blog #063 on Nov 16.

How’s your comfort level in thermography?
(The above comments represent my opinion).

Rod Hoff / Restoration Consultants Inc
Thermography Instructor / IR camera sales
3284 Ramos Circle, Sacramento CA 95827
toll free 888-617-3266 ext 301
fax 916-736-1134
rhoff@restcon.com

Provider of Fluke TiS, TiR, TiR1, Ti, Ti25, TiR27, Ti27, TiR29, Ti29, TiR32, Ti32, TiR3, and TiR4 infrared cameras.

See DEMO www.moistureview.com/demo.html

Posted in building envelope, Fluke, general, infrared cameras, Thermography | Tagged , , , , , , , | Leave a comment

Blog #061 – Your THERMOGRAPHY COMFORT LEVEL – Exercise #2 – insulation detection!

Review Blog #060 and continue with the exercise.

Cool wall cavity areas (darker color) and warmer wood framing (lighter color):

Scenario #3 – viewed from the outside during the heating season (winter) – is the wall insulated?

Scenario #4 – viewed from the inside during the heating season (winter) – is the wall insulated?

Excercise cool bay scenario

Excercise cool bay scenario

(Answers)

Scenario #3 – Insulated

Scenario #4 – No insulation

 Look for Scenarios #5 and #6 in Blog #062 on Nov 9.

How’s your comfort level in thermography?
(The above comments represent my opinion).

Rod Hoff / Restoration Consultants Inc
Thermography Instructor / IR camera sales
3284 Ramos Circle, Sacramento CA 95827
toll free 888-617-3266 ext 301
fax 916-736-1134
rhoff@restcon.com

Provider of Fluke TiS, TiR, TiR1, Ti, Ti25, TiR27, Ti27, TiR29, Ti29, TiR32, Ti32, TiR3, and TiR4 infrared cameras.

See DEMO www.moistureview.com/demo.html

Posted in building envelope, Fluke, general, infrared cameras, Thermography | Tagged , , , , , , , | Leave a comment

Blog #060 – Your THERMOGRAPHY COMFORT LEVEL – Exercise #1 – insulation detection!

Are you comfortable using your infrared camera to investigate insulation issues?  I’m going to give you a method to determine if the wall is fully insulated or not using your infrared camera.  You start with two basic steps:  Step #1-Identify the heat source and thus the direction of the heat flow!  Step #2-Identify the path of least resistance, the lowest R-factor.  Inspecting walls for insulation issues with an infrared camera requires an understanding of the 2nd Law of Thermodynamics.  That law defines the direction of heat flow and is simple:  hot goes to cold.  The speed with which “hot goes to cold” is affected by at least a couple of factors:  (1) the ∆T from surface to surface (the greater the temperature difference, the greater the conductive speed) and (2) the R-factor (the greater the R-factor or R-value, the slower the conductive speed).    In a fully insulated wall the framing members would be the path of least resistance and the  bay would be the path of most resistance to heat flow.  In a wall that does not have insulation the bay would have the lower R-value and thus be the path of least resistance and the framing members would have the higher R-value and thus be the path of most resistance.  Try to see this on a molecular level because that’s the way energy (heat) flows.

If you go back and read Blog #004 (Jan 10, 2011) you’ll see a brief discussion on the recommended ∆T  ( outside surface to inside surface ∆T of the wall being inspected).  Sometimes the difference in ambient temperatures (inside to outside) is sufficient.  But the influence of the sun and wind can change the outside surface temperature dramatically from the ambient temperature.  For example, the outside ambient temperature could be 30°F and the outside wall surface could be 120°F due to solar heat.  So, it’s a good idea to be aware of what’s happening on the outside of the wall that you are inspecting.  The recommended ∆T (temperature differential surface to surface) is 18°F or greater.  This is perhaps due to the nature of the R-value of materials.  R-values can be expressed as the temperature difference needed to transfer 1 BTU/hr/ft².  For example, R-19 value would require a 19° F temperature difference to transfer 1 BTU/hr/ ft².   1 BTU is  not of lot of heat transfer, is it?  The effect on the target wall that you are looking at is very small.  I was looking at an uninsulated wall with a 73°F inside surface temperature and a 47°F outside surface temperature.  That is a 26°F ∆T, well above the 18°F minimum suggested.   The area on the wall where the wood framing is located read 74.3°F.  The bay read 73°F.  That is only a 1.3°F temperature difference.  That’s why it’s important to have a “sensitive” infrared camera for this type of work.   The lower the ∆T from outside surface to inside surface, the less thermal effect you’ll see on the wall you are inspecting.  As mentioned, some infrared cameras are more sensitive than others and will pick up more detail.  (Get the most sensitive camera you can afford

In this blog #060 and the following three blogs I want to give you some exercises containing a variety of scenarios so that you can practice identifying insulation issues.  If you think your way through these exercises you’ll raise “your Thermography comfort level”

(Warm wall cavity areas (lighter color) and wood framing (darker color):

#1 scenario:  viewed from the outside during the heating season (winter) – Are the bays insulated?

#2 scenario:  viewed from the inside during the heating season (winter) – Are the bays insulated?

excercise warm bay scenario

excercise warm bay scenario

(Answers:)

Scenario #1 – no insulation

Scenario #2 – Insulated

Look for scenarios # 3 and #4 in blog #061 on Nov 2.

How’s your comfort level in thermography?
(The above comments represent my opinion).

Rod Hoff / Restoration Consultants Inc
Thermography Instructor / IR camera sales
3284 Ramos Circle, Sacramento CA 95827
toll free 888-617-3266 ext 301
fax 916-736-1134
rhoff@restcon.com

Provider of Fluke TiS, TiR, TiR1, Ti, Ti25, TiR27, Ti27, TiR29, Ti29, TiR32, Ti32, TiR3, and TiR4 infrared cameras.

See DEMO www.moistureview.com/demo.html

Posted in building envelope, Fluke, general, infrared cameras, Thermography | Tagged , , , , , , , | Leave a comment

Blog #059 – Your THERMOGRAPHY COMFORT LEVEL – NETD. What is it and why is it important?

When shopping for an IR camera one needs to match up certain features of the camera to the investigative needs of the thermographer.  So, we need to understand and look at “camera specifications” which are found in the “spec sheets”.  The most expensive thing you can do is get a camera that doesn’t fit your needs.  For example, is there a difference in the needs of a thermographer who is performing inspections on high ∆T (temperature difference) items (such as motors, electrical, etc) verses the thermographer who is performing inspections on small ∆T surfaces (interior/exterior building surfaces) ?  Yes!  This is where we become concerned about the “sensitivity” of the detector array in the camera.  Performing inspections on surfaces that have a 100 degree F differential does not require the same sensitivity as performing inspections on surfaces that have a 2 degree F differential.  For example, evaporative cooling usually results in a drop in temperature of only a few degrees F.  The more sensitive the detector array, the easier it will be to locate such issues.  When you look at a spec sheet for a particular camera, look for “thermal sensitivity” or the NETD (noise equivalent temperature differential).   You’ll usually see something like this:  ≤0.1 °C at 30°C target temp. (100mk);  or ≤0.07 °C at 30°C target temp. (70mk);  or ≤0.05 °C at 30°C target temp. (50mk).  The lower the number, the more sensitive the camera.  The 50mK infrared camera detector array is much more sensitive than the 100mK detector.   You’ll notice, too, that the lower the number the more expensive the camera.  I would not recommend a camera that has an NETD higher than 100mK. 

 The ASNT (American Society of NonDestructive Testing) says: “The noise equivalent temperature difference is also the primary index of the infrared thermographic system.  This index indicates the temperature resolution and shows the minimum detectable temperature difference appearing on a target surface whose emissivity ε is nearly equal to 1.0”…  “A smaller value indicates better temperature resolution of the system.”

 The images below show the capability of highly sensitive infrared cameras and this is what you need to perform a thorough job in building diagnostics.

Taken with a Fluke 70mK Ir camera

Taken with a Fluke 70mK Ir camera

 Notice that the framework is only .2° F (2/10 of a degree) cooler and the effect of the hot water pipe is less than a 2 degree F rise in temperature.

Fluke 50mK detector

Fluke 50mK detector

This image was taken with a Fluke Ti32 infrared camera  with a 50mK detector array.  Notice the detail and the sensitivity.  This camera can detect and collect greater detail which helps the thermographer who is performing energy audits home inspections and moisture investigations.

How’s your comfort level in thermography?
(The above comments represent my opinion).

Rod Hoff / Restoration Consultants Inc
Thermography Instructor / IR camera sales
3284 Ramos Circle, Sacramento CA 95827
toll free 888-617-3266 ext 301
fax 916-736-1134
rhoff@restcon.com

Provider of Fluke TiS, TiR, TiR1, Ti, Ti25, TiR27, Ti27, TiR29, Ti29, TiR32, Ti32, TiR3, and TiR4 infrared cameras.

See DEMO www.moistureview.com/demo.html

Posted in building envelope, Fluke, general, infrared cameras, Thermography | Tagged , , , , , , , | Leave a comment

Blog #058 – Your THERMOGRAPHY COMFORT LEVEL – Why use infrared for home inspections?

To answer that question we have to ask “Why do people choose to get a home inspection before buying a house?”  It’s to reduce the “RISK” factor.  The greater the investment, the greater the risk!  So, a trained home inspector offers a valuable product, his expertise in performing an examination of the building for possible problems.  The time to know about problems is obviously BEFORE the purchase so that problems can be negotiated in the price or fixed.  Home inspections are traditionally performed as a visual inspection with all of the limitations that come with visual inspections.  For example, can you, with your eyes, detect possible missing insulation?  No!  Can you, with your eyes, detect possible moisture issues in walls, floors, and ceilings if stains are not present or visible water is not present?  No!  And the person that hires a home inspector understands the limitations of a visual inspection.  That means that the reduction in “risk”, the thing that the customer is paying you for, is limited too.  What if you could further reduce your risk using a more in-depth inspection?  Does that sound attractive?  To many people it is not only attractive, but it is preferred.  The images below represent the results of two types of inspections:  visual inspection verses infrared inspection.  Which inspection would you want BEFORE you purchase this house?

No sign of a problem.

No sign of a problem

Now we see a possible problem

Now we see a possible problem

No indication of a problem

No indication of a problem

Now we see a problem

Now we see a problem

One of the advantages in using this Fluke IR Fusion camera is that you can demonstrate the infrared capability verses the visual capability.  Present the images like I did above and let the customer see the value of infrared.

How’s your comfort level in thermography?
(The above comments represent my opinion).

Rod Hoff / Restoration Consultants Inc
Thermography Instructor / IR camera sales
3284 Ramos Circle, Sacramento CA 95827
toll free 888-617-3266 ext 301
fax 916-736-1134
rhoff@restcon.com

Provider of Fluke TiS, TiR, TiR1, Ti, Ti25, TiR27, Ti27, TiR29, Ti29, TiR32, Ti32, TiR3, and TiR4 infrared cameras.

See DEMO www.moistureview.com/demo.html

Posted in building envelope, Fluke, general, infrared cameras, Thermography | Tagged , , , , , , , , | Leave a comment

Blog #057 – Your THERMOGRAPHY COMFORT LEVEL – Using IR – Flat roofs verses slanted roofs?

Are you comfortable when you are asked to perform a moisture investigation on a “roof”?  Roofs are notorious for water leaks and highly expensive to repair.  An infrared camera is a great tool for pointing us in the right direction to locate the failing membrane.  Remember, though, infrared cameras are not moisture meters and therefore are not used to “verify” the presence or absence of moisture.  I’ll refer to two kinds of roofs:  (1) flat roofs and (2) slanted roofs.  There is a greater application for thermography in finding moisture issues in flat roofs than slanted roofs.  Why?  Water ponds or settles right beneath the failing membrane when the roof is flat.  The water doesn’t usually run off to the side (unless there is a slant – thus the problem with slanted roofs).  There is an advantage to having the water settle right beneath the failing membrane, which is what should happen on a flat roof.  Using the principle of “thermal capacitance” a thermographer can identify “areas of investigation” where a moisture meter can be used to verify the presence of moisture.  How does this work?  During a sunny day the energy from the sun cooks the roof membrane and any water that is beneath it in the insulation.  So, we obviously need a “sunny day” as a prerequisite for flat roof moisture investigations using infrared cameras.  Water has a higher thermal capacitance than the roof membrane.  So, after the sun goes down, the roof membrane starts cooling down.  The water starts cooling down, too, but at a much slower rate.  The hot water will transfer heat to the membrane above it and keep it warmer than the adjacent dry areas.  When viewed with a thermal imaging camera you’ll easily see a warm area which is begging for more attention.  That’s when you pull out your moisture meter and verify and enjoy the fruits of your labor.

Caution!!!  Moisture investigations on flat roofs demand certain prerequisites.   The investigation needs to be done at night after the sun has gone down and the roof has had time to cool down.  And, as already mentioned, there is the need for heat from the sun, a sunny day.  So, cloudy, overcast days most often hinder the investigation.  And since wind cools things down, you need to make sure that your scan is done in a “no wind” situation.  Although the principle of thermal capacitance is simple and straight forward, flat roofs vary from building to building and can be very complicated.  Understanding the makeup of the roof layer by layer is very important.  Conductive heat transfer is a part of the equation in order to keep the roof membrane warm.  The success of conductive heat transfer is affected by the “path of least resistance” from the water to the membrane.  The  point is that the principles are easy, the roofs can be complex.  Know your roofs!!!

Image of moisture signature in flat roof

Image of moisture signature in flat roof

Due to the high thermal capacitance of water we can see a heat signature after the membrane has cooled off.
Can you use an infrared camera for slanted roof moisture investigations?  Yes, but not using the principle of thermal capacitance.  Water travels according to the direction of the slant and doesn’t have the time needed to heat up.  So, we use the principle of evaporative cooling and scan the roof from the inside.  If moisture reaches the underside surface of the roof you will usually experience evaporative cooling, which will drop the temperature of the wet area a few degrees F.  I hope these comments have raised your “comfort level”.

How’s your comfort level in thermography?
(The above comments represent my opinion).

Rod Hoff / Restoration Consultants Inc
Thermography Instructor / IR camera sales
3284 Ramos Circle, Sacramento CA 95827
toll free 888-617-3266 ext 301
fax 916-736-1134
rhoff@restcon.com

Provider of Fluke TiS, TiR, TiR1, Ti, Ti25, TiR27, Ti27, TiR29, Ti29, TiR32, Ti32, TiR3, and TiR4 infrared cameras.

See DEMO www.moistureview.com/demo.html

Posted in Fluke, general, infrared cameras, Thermography | Tagged , , , , , , , , | Leave a comment

Blog #056 – Your THERMOGRAPHY COMFORT LEVEL – Specular verses Diffuse

The question comes up sometimes about the reflectivity of glass, since it has a high emissivity of .92.  If the emissivity is .92 the reflectivity is .08.  So why can I see my infrared reflection when pointing my infrared camera toward glass?  Two words the thermographer needs to add to his vocabulary if he haven’t already: specularity and diffusivity.  Specular reflector is defined by ASNT as: “Smooth reflecting surface that reflects all incident radiant energy at an angle complementary (equal around the normal) to the angle of incidence.  A mirror is a specular reflector.”  Diffuse reflector is defined by ASNT as: “Surface that reflects a portion of the incident radiation in such a manner that the reflected radiation is equal in all directions.  A mirror is not a diffuse reflector.”

What is glass made of?  Sand!  Both sand and glass have a high IR emissivity and a low IR reflectivity.  You can see your IR reflection in glass but not in sandpaper.  Why?  Glass is a good example of a specular surface and sandpaper is a good example of a diffuse surface.  Water has a very high emissivity – .98.  And yet you can see the IR reflection of the sun in the water using your infrared camera.  

I took an image with my Fluke Ti32 infrared camera so that I could have both the visible light image and the infrared image.  These two images are really the same image.  One is blended down to 100% visible light and the other is blended to 100% infrared in the picture-in-picture mode.   I saved them as two different images and then exported them to the jpg file format.  In the first image (the 100% visible light image) you can see the glass window with a piece of sand paper being held up.   In the second image (with the 100% infrared) you can see my IR reflection in the glass but not in the sandpaper held below my head.  Although both the sandpaper and glass have a high emissivity you see a reflection only in the glass.  Why?  Again, the glass is specular and the sandpaper is diffuse.  On a hot day in the summer time you can get a “cold” reading on glass if you are standing at an angle where your infrared camera is catching a reflection of the sky.  Hopefully you will be more comfortable now when you run into these situations.

visible light image of sand paper and glass

visible light image of sand paper and glass

"infrared of sand paper and glass

infrared of sand paper and glass

How’s your comfort level in thermography?
(The above comments represent my opinion).

Rod Hoff / Restoration Consultants Inc
Thermography Instructor / IR camera sales
3284 Ramos Circle, Sacramento CA 95827
toll free 888-617-3266 ext 301
fax 916-736-1134
rhoff@restcon.com

Provider of Fluke TiS, TiR, TiR1, Ti, Ti25, TiR27, Ti27, TiR29, Ti29, TiR32, Ti32, TiR3, and TiR4 infrared cameras.

See DEMO www.moistureview.com/demo.html

Posted in building envelope, Fluke, general, infrared cameras, Thermography | Tagged , , , , , , , | Leave a comment

Fluke Thermal CashBack Promotion

Get some relief from the economy and get cash back when you purchase a qualifying Fluke Thermal Imager.

$1,000 rebate with purchase of Ti32 or TiR32 Thermal Imager

$750 rebate with purchase of Ti29 or TiR29 Thermal Imager

$500 rebate with purchase of Ti27 or TiR27 Thermal Imager

Purchase a qualifying Fluke thermal imager between Sept 1, 2011 and Dec 31, 2011 and get Cash Back.

For a discussion of the feature differences in these high resolution cameras in the Fluke P3 Series, call me (Rod Hoff) at 888-617-3266 ext 301.

How’s your comfort level in thermography?
(The above comments represent my opinion).

Rod Hoff / Restoration Consultants Inc
Thermography Instructor / IR camera sales
3284 Ramos Circle, Sacramento CA 95827
toll free 888-617-3266 ext 301
fax 916-736-1134
rhoff@restcon.com

Provider of Fluke TiS, TiR, TiR1, Ti, Ti25, TiR27, Ti27, TiR29, Ti29, TiR32, Ti32, TiR3, and TiR4 infrared cameras.

See DEMO www.moistureview.com/demo.html

Posted in building envelope, Fluke, general, infrared cameras, Thermography | Tagged , , , , , , , , | Leave a comment