Author Archives: ibd2013

Comparing Infrared and Capacitance Moisture Inspections

Two of the most used non-destructive inspection technologies are infrared thermography and capacitance.  There are pros and cons to using either.

IR_90841a  IMG_3852

How each technology works.

Roof surfaces emit infrared energy which is viewable using an imaging radiometer (infrared camera).  When the inside/outside temperature of a roof assembly is sufficiently different, areas of the assembly  that contain wet insulation will conduct more energy to the surface and the surface will radiate more energy, allowing the thermographer to locate patterns in real time that distinguish  between the wet and dry areas to be marked on the roof surface.

Capacitance meters use two pads a few inches apart to read the electrical characteristics of the roof assembly below the meter.  Dry material below a dry membrane yields a zero reading while wet materials will yield a positive reading. Readings are taken on a grid pattern.  Wet readings are grouped together and marked as a wet area on the roof surface.

Coverage

Infrared requires the surface to be clear and viewable.  Areas that are under equipment or covered in water, loose equipment or debris are not viewable.  The roof has to be the same construction and under the same energy influence.  Radiated energy from walls or equipment and convection energy from roof units or wall louvers will affect the surface temperatures.

Capacitance meters only read the location below the meter.  A good meter is sensitive enough to detect trace moisture.  The reading can be considered to represent a larger area depending on the type of insulation and roof construction.

Advantages

Infrared provides an image of the wet area which may help identify the source.  Infrared may locate a smaller area that a capacitance grid could miss or wet insulation under a dry layer that a capacitance meter would not detect.

Capacitance can be used during the daytime and require less trips or time on site.  Capacitance can detect trace moisture that may not affect the surface temperature enough for infrared to see a pattern.

Limitations

Infrared thermography requires a dry surface at the time of the inspection and for a period of time before the inspection.  There must be an inside/outside temperature difference of the roof assembly in order to provide the energy to conduct to and radiate from the surface.  Wet areas may be masked by sufficient energy from walls, roof units, or anything that can influence the surface temperature.

Capacitance requires a dry surface at the time of the inspection.  The readings are spot and taken on a grid.  A small wet area in between grid points may be missed.  The meter cannot distinguish lighter moisture near the surface from heavier moisture in the top layer of insulation.

A Real Life Comparison

Recently we had the chance to compare the two head to head on a small modified roof.  We performed the capacitance inspection first by walking every other run of the membrane taking a reading every 5-6 feet.  We located and defined 3 wet areas by taking additional readings around the positive readings until we encountered negative readings in each direction.  After the roof cooled, the same areas were located and no additional areas were discovered.  The left photo is after locating and marking one of the wet areas using the capacitance meter with the dots indicating a wet reading and the No Symbols indicating a dry reading.  The thermogram is of the same area after the roof had cooled.  Looking close at the thermogram, one can see the marks from the capacitance inspection.

Either technology would have worked and found all there was to find on this roof under the conditions and at the time of the inspections.

IMG_5863a  WA 1

Which is best for your roof?

It depends.  Generally, if one layer of Perlite or wood fiber, a capacitance inspection may give the best bang for the buck. Multiple layers or where you want to find where the core of Polyisocyanurate has wet, infrared can provide more information. When the entire condition of the roof is desired a combination of infrared and capacitance will provide information about the plies, the top layer of insulation and lower layers.  And for some roofs a nuclear moisture inspection may be a better fit than either, but that’s another article.

This article is written primarily considering low-slope roofing.  The same applies to other similar constructions such as insulated wall assemblies or insulated steep-slope roofing.

Capacitance Roof Moisture Inspections

Capacitance roof moisture meters can be used to trace leaks or perform a complete roof moisture inspection.

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Positive reading next to an obvious hole in the roof membrane.

Tracing leaks is accomplished by taking readings in the problem area, noting the positive readings and their level and looking for the highest readings which often indicates the source.

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Pegged reading and paint mark to indicate the positive reading.

Full roof moisture inspections are performed by taking readings on a grid pattern over the entire roof.  When a positive reading is found, additional readings are made in each direction until a negative reading indicates dry material.

IMG_1047
Wet area located and defined using the capacitance roof moisture meter.

 

Find the Cold Air at the Source

Do you have any cold locations in your home, office or other building.  Sometimes it’s easy to find the source when you can feel the air around a door, window or wall outlet.  Other times, it’s not so obvious and that’s when we may be able to help.

This first image is showing cool trails from where cold outside air is flowing in under a baseboard.  You could probably find a problem like this feeling along the floor with you hands.  The infrared camera makes it quick and easy to locate and show the extent of the problem visually .

infrared thermogram air leak
Air leak under baseboard of wall.

 

This second image shows one cool stud space above the window and indicates missing insulation.  You would not feel air flow, but might feel the cold from this cool spot on the wall and it could feel like a cold draft of air.  These are the elusive type of problem which are hard to find without using an infrared camera.

Missing insulation above window
Missing insulation above window

 

This third image is a similar problem to the first and shows air flow under a window sill.  You might find this by feeling around the window with your hands, but may mistake it for air entry around the electrical boxes.

Air infiltration under a window sill.
Air infiltration under a window sill.

Trace Leaks to the Source

IBD can use several non-destructive ways to trace leaks to their source.  See below or download Trace Leaks to the Source.

 

IR_90841a
Leak source located at vent pipe using infrared .
IR_93262
Two leaks located on ballasted EPDM roof using infrared
IR_0222a
Area of wet insulation as seen from below a metal deck on an EPDM roof.
IR_0102a
Locating where leak reaches the metal deck using infrared.
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Active leaks at fasteners on a metal roof using infrared.
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Leak traced to vent pipe using a capacitance roof moisture meter.

 

Thermography Brief – Moisture in Ballasted Roofs

Infrared thermography can be used to locate wet insulation in a ballasted single-ply roof system. The ballast stone does increase the challenge and may require waiting longer after sunset to start an inspection. A higher vantage point can help to pinpoint areas for closer inspection. The standards call for a large inside/outside temperature difference, but this is not always necessary. The main condition is that the ballast stone is spread evenly and has a uniform depth.


Ballasted_04

The wet area is around the vent and extends diagonal toward the lower left of the thermogram. See next image for a more defined view from above.  Ballasted EPDM / EPS insulation / concrete deck. Outside temperature was 73F+/-.


Ballasted_05

The above image shows the same wet area of the first image, but taken from a the vantage point of a higher roof level.  Ballasted EPDM / EPS insulation / concrete deck. Outside temperature was 73F+/-.


Ballasted_06

EPS insulation wets (absorbs moisture) very slowly and a small wet area like this one only 1-2 feet wide will appear amorphous.  Ballasted EPDM / EPS insulation / concrete deck. Outside temperature was 73F+/-.


Ballasted_07

A distinct board pattern extending from below a raised walkway on the right side. Ballasted EPDM / Polyisocyanurate insulation. Outside temperature was 34F+/-.

Download the PDF version of this Thermography Brief.

Thermography Application Courses

IR Inspection of Building Envelopes & Roofs is a two-day theory and application course for the use of thermal imaging to locate and evaluate energy loss and moisture problems within building envelopes and insulated roofing systems. This is a non-certification course that focuses on these specific applications. Course attendance may be applied to training requirements for thermographer certification.

This course covers infrared theory, heat transfer concepts, equipment operation and selection, standards compliance, image analysis and report generation.

Students are trained to identify and document thermal patterns caused by improper design, workmanship or material failure. Attendees are encouraged to bring their own imager for individualized training or to learn how to use it more effectively.

Course tuition includes all course presentations, Course Reference Manual and Certificate of Completion. Courses usually begin at 8 am on the first day and end at 5:00 pm on the second day.

Prerequisite: None

For fees and registration information contact us .

Certified Infrared Thermographer

Level I Certified Infrared Thermographer® is a five-day course for the application of qualitative thermal imaging for P/PM, Condition Assessment, Condition Monitoring, Quality Assurance, Forensic Investigations, and Building Sciences.

This course covers infrared theory, heat transfer concepts, equipment operation and selection, standards compliance, image analysis and report generation.

Students are trained to identify and document thermal patterns caused by improper design, workmanship or material failure. Specific applications include: electrical distribution systems, mechanical systems, steam systems, refractory systems, underground piping, active thermography, building envelopes and flat roofs.

Students are encouraged to bring their own imager for individualized training or to learn how to use it more effectively.

Course tuition includes all course presentations, Student Reference Manual, and Infraspection Institute Certified Infrared Thermographer® exam. Certification card and diploma issued with passing grade of 80%. Course is approved by the InterNational Association of Certified Home Inspectors and meets the training requirements for their Infrared Certified professional designation and logo.

Classes begin at 8 am daily Monday through Friday. Class ends by noon Friday.

Prerequisite: None

For fees and registration information contact us .

Infrared Electrical & Rotating Equipment Inspections

Opportunities to improve system performance by reducing unplanned outages and repairs.

  • Identify and document exceptions in electrical systems that are caused by deteriorated connections, short circuits, overloads or other problems.
  • NFPA 70B recommends infrared inspections of electrical equipment annually Identify and document exceptions in rotating equipment that are caused by friction due to improper lubrication, misalignment, worn components or other problems.
  • Scan before shutdown to locate minor problems for timely repairs
Thermogram showing exception related to fuse box
Thermogram showing exception related to fuse box
Matching photo to thermogram of fuse exception
Matching photo to thermogram of fuse exception

 

 

 

 

 

 

 

 

 

 

Thermogram of electrical exception related to cabling.
Thermogram of electrical exception related to cabling.
Matching photo to thermgram of cable exception.
Matching photo to thermgram of cable exception.