by Ron Lucier
ITC Regional Thermography Course Manager

Yes, sports fans. It is time for the Boston Red Sox to begin another season which, as in the past 87 years will lead us to cry “maybe next year?” in October. Coinciding with our annual disappointment is the start of the roof inspection season in the Northern climates. As I have been getting many calls about this topic I feel that it is necessary to address journalism’s 5 W’s and H regarding infrared roof inspections.

Who? You. There are certain skills that the average infrared thermographer needs to acquire prior to becoming successful at roof inspection. Roof knowledge is essential. I highly recommend the courses that the Roof Consultants Institute periodically offers (http://www.rci-online.org). RCI is also a source for certified roof consultants – experts in roofing. While not required for every inspection, these folks have incredible experience. The biggest skill you need to require is PATIENCE. Infrared thermographers are accustomed to instant results – look at a bearing or piece of electrical switchgear and as long as either are in operation, analytical data is probably present. Unfortunately that is not the case with a roof. The Physics of radiation and heat transfer teach us that there are only certain times of the day and night that are appropriate for an inspection. More on this topic later.

What? The typical infrared inspection is on “low-slope” commercial roofs. Please do not refer to these as flat roofs – your credibility will be in question. A roof must be pitched (sloped) so that water can drain off. If it was truly flat it would not technically be a roof but a very shallow swimming pool when it rained. There are some infrared applications for residential roofs but I will address those in a future article.

Why? A roof seems like a very simple concept but in fact roofs are integrated systems that provide structural integrity, prevent water intrusion and provide building insulation. When a roof fails the most common effect is the introduction of water into the roof system, primarily into the insulation. This has negative consequences – extra weight, loss of R-value for the insulation and potential damage to the materials and equipment inside. An infrared inspection can locate the wet areas and only those areas may need to be repaired. Repairing 5000 square feet of roof is much less expensive than replacing 100,000 square feet.

How? There is an ASTM procedure available to help you become familiar with roof inspections (ASTM C1153 available from http://www.astm.org). This is the standard guideline that has been in use for over 15 years. It provides a good – but not perfect – approach to general roof inspections. The two methods that are covered are the walk over method and the fly over method. It does not address my favorite technique the walk under method (done during the morning so I can sleep at night…).

When? That is the big question and is the focus of our two day roofing course. The general requirements happen only a few times a year in most locations. Weather is usually the biggest factor in affecting the quality of the survey or even if the survey can be accomplished.

Safety! Thermographers have fallen from roofs and lost their lives. The subject of roof safety could be addressed in an article this size all by itself. In general I prefer two helpers in addition to the thermographer. One helper marks the locations of the thermal indications, the other watches out for those performing the inspection. Preceding an inspection a walk on the roof in daylight is strongly recommended as well as an inspection of the structure underneath the roof. Roofs do have a history of collapse.

Special Issue - ASTM C1153 was written when most of the cameras in operation were short-wave. Most of the infrared cameras sold today are long-wave. These work fine on most roofs but certain membranes, particularly black EPDM, under certain conditions (clear sky) the roof looks like a mirror! The emissivity of black EPDM is high in the long-wave (about 0.92). We are accustomed to think that this should help us but if the roof is cold – below 40 ºF and there is a clear sky (really cold), the roof is very efficient at reflecting the cold sky. The image to the right shows reflections and the warm areas associated with a large leak.  The good news is that the inspections can be done but be aware of the potential for significant reflection.

Conclusion – The use of infrared for roof inspections has an extensive history of success (I have been inspecting roofs with IR since 1984). There is a wealth of information presented in our roof course so if you wish to learn more – or come and teach us a few things – please register for one.

Click here to learn more about the roofing course and see the class schedules.

Thermographers know their animal thermal imprints, at least when it comes to lying dogs. We had a record number of correct responses for last months Brainteaser. Bob Madding was the first to guess correctly, but I had to disqualify him for being part of the ITC staff! But Jeff Long at New York Power Authority sent me a correct answer only 2 minutes after Bob, so he is our winner.

Thanks to Donna Harper, D.V.M. for contributing the canine thermal signature.

Brainteaser of the Month  [top]

Here is this month's brainteaser. This is a tough one, so I'll give you a clue. The thermogram is a result of changes made to a wall structure. First reader to email me with the correct explanation wins $20 in Infrabucks. Please put "Brainteaser" as the subject of the message.

Click here to email your guess

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