Flat Roof Inspection Question - White Color

I have a rather LARGE commercial building with a roof that is covered in a white Acrylic material. The layers on this roof are (from bottom) :

  1. Concrete Deck
  2. Vapor/moisture Barrier
  3. 3.5 inches Dow Board (that insulating type)
  4. Acrylic overlay membrane (white)

I know the prevailing wisdom is to shoot a flat roof at sunset/night…and this is how I have done all my others, but now I am wondering on this roof …if it would be better shot in the morning, as the sun begins to load up this white acrylic cover.

I would guess at this point the “colder” areas would show possible water damage, as they would be the slowest to thermally load.

Or does the “color” make no difference?

I would appreciate your thoughts. Thank you in advance.

Hi Rob,

It can be done BUT there are many limitations and hurdles to overcome and understanding thermal loading and thermodynamics is paramount.

I played like Peter Pan chasing my shadow on one I performed… :slight_smile:

These were early morning right at sun up.

My shadow… you can see exactly where I was standing

Object shadows…
cool shot.jpg

You’re on the right track… and possibly comparisons between the two times can assist you in determining your answers.

cool shot.jpg

General recommendations for inspections on roof is 2 hours after sun up or down down. I have seen that not always hold true though. I believe that the white roof will not absorb sun radiation as quickly but we may only be talking about a half hour difference or so. I would recommend waiting a little while after sun up for a day inspection and for night during this time of year you should be able to get there any time from now to 2 hours after sun down.

OJ Utter
Level III Thermographer

Dear Rob:

IR Inspections of Flat Roofs is a previous topic that can be found in the Tip of the Week section at the IRINFO.ORG website. It can be found at the following URL:

Several other Tips and Feature Articles pertaining to infrared inspections of roofs are available free of charge.

As to your question regarding roof membrane color, do not confuse albedo with emiitance. White roofs will absorb plenty of heat from the Sun during daylight hours and should be inspected from around sunset until several hours thereafter.

When inspecting after sunset, your actual window of opportunity will depend upon several interelated factors including, but not limited to: local weather conditions before and during the inspection, roof moisture content, roof surface conditions, and the sensitivity of your thermal imager.

To ensure accuracy, all infrared data should be verified by invasive testing.

To help ensure best results, you might also wish to obtain a copy of Infraspection Institute’s Standard for Infrared Inspection of Insulated Roofs. This comprehensive 11 page document is available from the Standards Section of the Infraspection Online Store.

Please feel free to give me a call should you require further assistance or information.

Hope this helps.

Thanks to all who responded. Jim I did purchase your specs for roof inspection. Very informative and will use sections of it in future specifications/quotes.

It did not however shed light on this particular question so I guess a bit of trial and error is in order.

Now a quick last question:

This roof is LARGE and I think I would like to use some flood lights at night to help in getting around. I don’t think this light will make any impact on the thermal images but might help me from falling on things. The light itself should have no impact on the thermal load. So the question is:

Can I use large floodlights at night when taking thermal images on a roof?

Thanks again.


I perform all my flat roof inspections 1 hour after sunset, no matter what color the roofing material is. As long as you perform these roof inspections after sun-down (having no sun reflection, will allow roof to cool down to normal temperatures), your IR camera will absolutely detect any moisture intrusion within the roofing material.

As for the floodlight use…Light will not make a difference in IR readings as long as the flood light is not beaming in one location more than a few minutes, your IR readings will not be affected. I’d only be concerned with heat build-up at the lit-up areas of the roof. Simply keep the light moving.

Here’s a nice IR image of a roof leak that was occurring at a college in Massachusetts. They had no idea where the source was until I arrived…

Here’s the same college at a different roof…

Note that the moisture intrusion (on the underside of the roofing material) will be warmer due to the conditioned area below.


Two questions, is that a Duro-Last roof system? And are those walk pads loose or glued to the membrane?

It has been my experience that moisture will be detected below walk pads if not glued to the roof membrane. Not necessarily a moisture issue, in fact if these pads are removed (if not glued) the moisture/water is visible.


I believe Rob is referring to a Thermoplastic roof membrane. Are you of the opinion that a thermal scan can be performed on this roof membrane? I have never attempted a scan on a roof membrane such as this although I have visually inspected a few roofs with this system. I’m of the opinion that it would be difficult at best if not impossible to do a scan on this roof system.


My advice for what it’s worth is:

  • Map out the roof the day before the scan and note all obstacles and limitations. This will also afford you the opportunity to do a visual.
  • Do not use flood lights (it will play havoc with your eyes)
  • Inspect the roof with a partner. He/She should be with you at all times. We sometimes get “tunnel vision” when scanning.
  • Have a cell phone with you.
  • If you are using a ladder to gain access to the roof make sure you tie the ladder. Can you imagine if the ladder is not there when you finish the job!!
  • Notify your local police department of your intentions (citizens will contact the police, trust me on this one)
  • Be aware of your surroundings at all times
  • Know your limitations and also your camera’s limitations.

Good luck and be safe!!

You could use LED flood lights, they produce almost no heat. There are several systems available. We do not sell them but check out Lowe’s or Home Depot, they both carry them. David is right that light will mess with your eyes, but if you cannot see you cannot see. LED’s are a lot more focused so the flood effect on your eyes will not be as bad.

One thing in all of these threads for flat roof inspections that I have noticed is no mention of fall protection. All of these commercial structures are required to provide you guys with tie offs for fall protection. Most of the time it is a cable or rope type of system around the outter edge of the structure. If they have one central tie off you can talk to the building owner about purchasing a retractable lifelife system as well. That will get you around the entire roof without having to constantly having to re-attach. I know HVAC service guys that have to get their own retractable lifeline systems then have the building owner provide a slightly elevated tie off for the retractable.

My manufacture for fall protection is owned by 3M and if you guys have any questions on that stuff feel free to email me and I can forward it on to the right person in the area that the building is in.

Jason Kaylor – JJ
VP of Sales
AC Tool Supply](http://www.aikencolon.com/)
Fluke Thermal Imagers](http://www.aikencolon.com/Fluke-IR-Thermal-Imagers_c_578.html)
FLIR Thermal Imagers
Fluke TiR1 Resources
FLIR B60 Resources](http://www.aikencolon.com/FLIR-Infrared-Imaging-b60-b-60-IR-Thermal-Imager-Camera_p_1564.html)
Retrotec Duct & Blower Door](http://www.aikencolon.com/Retrotec-Air-Blower-Door-Duct-Systems_c_1074.html)

Fall Protection Usually required if working within 6’ of roof edge if I recall correctly.

I think I paid around $150.00 for the basic set up. Any inspector who walks roofs should have one.


That’s a very good point Jason!
BTW Have you ever worked with a harness? It’s cumbersome to say the least.

Here’s the link I posted www.blackbearladder.com click on the fall protection link.
I agree Mario, they are a pain but save lives, not to mention if OSHA happens to be driving by and sees you without it you’ll get fined. It happened to me and the fine was $1500.00 but I negotiated it down to $750.00.

I’m not sure if there is a clause in the Reg’s. I seem to remember roof inspection being excluded but I think that’s more geared to set up for construction.

Agreed Peter!

Fall protection, and just safety in general is one of our main lines. Get a comfortable one. Most distributors do not carry the higher end ones, so often guys get stuck buying cheap harnesses. Yes they are still cumbersome just because it is an extra layer that you are not use to.

The top two in this list are about as comfortable as it gets for harnesses:


Those start around $175, in contrast the normal OSHA compliance harness and lanyard we sell for $72.50, which is what you will see at most places. Its like anything else you get what ya pay for.

Jason Kaylor – JJ
VP of Sales
AC Tool Supply](http://www.aikencolon.com/)
Fluke Thermal Imagers
FLIR Thermal Imagers
Fluke TiR1 Resources
FLIR B60 Resources](http://www.aikencolon.com/FLIR-Infrared-Imaging-b60-b-60-IR-Thermal-Imager-Camera_p_1564.html)
Retrotec Duct & Blower Door](http://www.aikencolon.com/Retrotec-Air-Blower-Door-Duct-Systems_c_1074.html)

Dear Rob:

Thank you for your purchase of the Infraspection Institute Standard for Infrared Inspection of Insulated Roofs. We are glad you found it useful.

Using flood lights on a roof is possible as long as they do not cause heating of the membrane in the areas to be inspected. In the 25 years that I have been conducting infrared inspections of large roofs, I have never used any type of floodlight. Instead, I have always relied on my thermal imager, available ambient light, and a good flashlight(s) when necessary.

You will note that the Infraspection Standard calls for a minimum of two people to be present on a roof as a safety precaution. Both should familiarize themselves with the roof prior to sunset and always be certain of their footing.

Unfortunately, IR inspections of flat roofs is topic that cannot be fully explored either in print or via a message board. As such, our best recommendation to anyone wishing to add thermal imaging to their services is to seek appropriate training.

Infrared inspection of flat roofs is a topic that is covered in depth in our Level I Certified Infrared Thermographer® training course. The topic is also equally covered in our applications course, IR Inspections for Home & Building Inspectors which is available to NACHI members for $500. Both courses are available as open enrollment classes or via our Distance Learning Program.

I would welcome the opportunity to work with you during an upcoming course where I am certain we can provide you with information to help ensure your success.

I hope this helps and wish you the best with your inspection.

Dear Mario:

IR inspections can be performed for flat or low slope roofs consisting of either a built up or single-ply membrane installed over, and in continuous contact with, a layer of insulation or an insulating deck. Roof may be either smooth, granule or gravel surfaced. If gravel surfaced, stones should be pea sized or smaller.

Spray applied foam roofs may also be similarly inspected.

For single ply roofs, membrane material may consist of of EPDM, modified bitumen or thermoplastic materials. While thermoplastics have a glossy surface, their emittance is still quite high.

As stated before, membrane color will not affect the inspection; however, any smooth-surfaced membrane, including black asphalt, roof can be quite reflective. This phenomena is especially noticeable during inspections conducted from rooftop level with a handheld imager. It will be even more noticeable if the roof has an aluminum coating and/or one is inspecting on a clear, cold night. Under such conditions, it is possible to miss significant quantities of moisture regardless of how careful the thermographer is.

To help offset the reflectivity of smooth membranes, I use a short wave imager whenever inspecting any smooth-surfaced roof. During the past 25 years, I have inspected millions of square feet of flat roofs and have never had a problem getting good results on TPO, PVC, EPDM, or BUR.

Unfortunately, portable SW imagers are no longer being produced on a large scale. Flir Systems does offer refurbished SW imagers with a warranty. Although SW imagers are more expensive that microbolometers, they can mean the difference between being able to perform an inspection or not.

Infrared Inspections of Smooth Surfaced Roofs is a topic I recently authored for IRINFO.ORG. Should you be interested, it can be found at the following URL:


Hope this helps.

Excellent advice Mario!