can you tell me the margin of error in flat top inspection ? I just did one and there was a big hot spot during the night and cold in the morning.  The roof is made of non absorbent insulation covered with a layer of grey asphalt ( no gravel ). Nothing inside the company at the location of the hot spot could cause the temp. variation on the roof.  It was not reflection either.

The hot spot could be caused by the thickness of the roof coating at that location. Heavy thick areas of coatings will retain heat and cold longer. The way I would check it would be to cut a core or try a Tramex moisture meter calibrated for roofing.  Do you have a visual of the area?

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Al Kravitz
Roof Consultants, Inc.
alkrav@roofconsultantsinc.com
www.roofconsultantsinc.com

Yes I do but the picture is small, I had some prob with the compression for your site.  I can e-mail you a bigger one if you like.  As you can see, the form is not square or rectangle as we  normally expect to see.  the roof is 140 X 160 Ft and this defect if it is one is abour 12 X 15 Ft

 Thanks

 Louis

Just as a side note, there is a lot of reflection in your image.  Short wave works much better, and in some situations, is the only type of imager that will work on a flat roof.  I would back up your findings with a core sample, mositure meter and/or nuclear testing.

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See if you can send me a visual image as well as the non compressed IR image so I can make some sense of this.

I too see a lot of reflection in the image but it is too small to determine the problem

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Al Kravitz
Roof Consultants, Inc.
alkrav@roofconsultantsinc.com
www.roofconsultantsinc.com

Louis-Andre,

There are always factors to consider when doing a roof survey - reflections, thick tar, mounds of gravel, dirty spots, time of day, heating/cooling conditions - and on and on... But, from your question, it looks like you've considered many of these already:  1. You did the survey both in the evening and the morning.  2. You researched the materials - non-absorbent insulation and grey asphalt (roll roofing).  3. You researched other causes for the heating you detected.  4. You already determined that the heat was not from a reflection.

It sounds like you did everything right, and looks like you took a good photo.  You've limited your margin of error as much as possible.  That said, we are still only photographers at this point.  Present your photos, the conditions under which they were taken, even research/articles to back up why youv'e taken the photos if you have to.  But, ultimately this is where your job as a thermographer ends.  You've provided the information to lead your customer to the next phase - further testing.  Yes, you could do capacitance meter or other testing to help verify your findings.  But as a thermographer you are done.

To this particular photo - roll roofing is an excellent emitter, water could stand on the non-absorbent insulation, it would show up warm at night (following good solar loading), it could show up cool in the morning as the sun is just starting to warm the roof.  It sounds like a winner.  Test it... it's easy to do on asphalt with a Tramex.  If you are going to do roofs - at Tramex Capacitance Meter needs to be in your toolbox. 

Best regards,

Thomas Kremser

Altheus Infrared, Inc.

www.AltheusIR.com