Message Board Thread - "Roof scan"

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Roof scan Darrin 9/1/2006
I did a scan on the roof of our leased building last night.. the conditions were perfect, hadn't rained for 2 days, sun beating down on the roof all day, clear, cool night etc..
The roof is a rubber membrane with 1 1/2" stone ballast and I know there are problems with leaks in other units that they have not been able to correct.During my scan I noticed the ballast on most of the roof radiated hot with the exception of 1 area. Since I thought I'd be looking for a warmer area as being the problem spot I am a little confused. Could the wet area of the roof be sucking the heat from the stone ballast making it appear cooler than the rest of the roof?
 
Re:Roof scan Al 9/1/2006
Ballasted EPDM membrane roofs are very difficult if not impossible to scan. It may be that your cool area has less ballast per s.f. than the rest of the roof due to wind erosion. Specs for the installation call for 10lbs per s.f. in the field of the roof, 12 lbs at the perimeters and 15 lbs in the corners. The amount of dirt build up between the rocks will also give hot images.
You may want to try scanning the underside of the deck in the morning to find cool areas that show moisture in the system.
 
Re:Roof scan Darrin 9/5/2006
Thanks for the tip!
 
Re: Roof scan Greg @ AITscan 9/8/2006
Hello:
You have to survey ballasted EPDM's just after dark. Because the rocks absorb a good deal of the energy during the day, the substrate (where the insulation is) gives up what little energy it has, as soon as the sun goes down.
Greg S.
greg@stocktoninfrared.com
 
Re:Roof scan gordo 9/8/2006
In my experience as a roof thermographer, loose-laid ballasted EPDM roof assemblies are difficult to obtain useful thermographic readings.

Ballast of large diameter,round washed river rock, particularly following warm, sunny days, will provide a "barrier" to being able to determine for moisture entrapped insulation below the membrane surface. I.e., you're reading the rock, not the assembly below the rock.

Also, the type of insulation utilized beneath the single-ply insulation is often expanded foam insulation (polystyrene or other), which will typically resist moisture absorption.

An alternative to trying and detecting leaks or entrapped damaged components from the exterior surface would be using the thermal imager on the inside. If moisture is present in the assembly, and active leakage is occurring, and you have a steel deck that you can see, take the imager and scan the underside. Moisture present within the flutes of the deck will typically be "colder" than the deck itself, andf the imager will be able to identify the difference. If the leakage is active, standing under the leak, scanning upward, you may be able to see the "pool" of moisture accumulating at the opening in the deck. Once you have identified the "pool", you may be able to see a "cold stream" (dark line) trailing towards the "pool". Where the cold stream ends is typically where your membrane opening is located. The key to scanning loose-laid, ballasted, single-ply EPDM roof assemblies from the interior is being able to see the underside of the structural metal decking, which might be hidden by a dropped ceiling system.

 
Re:Roof scan BrianC 9/8/2006
I have scaned hundreds of ballast roofs including stone and pavers and have had great success in locating wet materials. It is difficult but not impossible. You must have a good working knowledge of roof assemblies and a very sensitive camera. From your scan it looks like an area where the ballast is thin. When scanning a stone ballast roof you must move the ballast around in some areas to determine if it is a heavy or light deposit. After a while you will learn the difference. It also helps to wait later at night to let the stone cool.
 


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