Non-Destructive Testing Services
The primary purpose of non-destructive testing is to identify and quantify areas of wet insulation within conventional low-slope roof systems. In many cases, non-destructive testing can provide a snapshot of the overall condition of the roof system beyond what can be seen on a visual basis.
Non-destructive testing may be utilized as a maintenance tool for several reasons such as justification that the roof is in a failure mode and in need of replacement, identifying problem areas before they manifest themselves as interior leak conditions and identifying areas of wet insulation for the purpose of energy savings due to lost R value.
Non-Destruction Testing Methods
There are three different methods of non-destructive testing to identify the presence of wet insulation; Infrared, Nuclear, and Capacitance. Roof Maintenance Systems can help you determine the best choice and value for your particular applications.
Infrared thermography utilizes an infrared imaging camera to detect heat or thermal energy patterns emitted from insulated conventional low-slope roof systems. Dry insulation will not hold heat; wet insulation will. Infrared must be performed in the evening hours after the roof surface has cooled to near ambient temperatures. Wet insulation will hold heat through solar loading and/or heat loss from the building interior.
The imaging camera will provide views of the wet insulation similar to how a video camera sees visible light. This allows the areas of wet insulation to be outlined in paint on the roof surface for easy identification and repairs where feasible.
Infrared is the most common and least expensive method of non-destructive testing. Some limitations include ballasted roof systems and roof systems with significant shading during the day preventing wet areas of insulation from solar loading.
Nuclear roof moisture surveys are a technique utilizing a radioactive isotope to emit high speed neutrons aimed at the roof from the roof surface. The presence of hydrogen atoms (water) slows the fast neutrons. The instrument sending the neutrons measures the rate of thermalization of the neutrons identifying areas of wet insulation.
Nuclear roof surveys are performed in a grid pattern usually 10’ x 10’ but can also be done at grids of 5’ x 5’, though the small grid size is substantially more expensive. This information is utilized to develop a computerized map indicating anticipated locations of wet insulation.
Nuclear scans are significantly more expensive than infrared, but unlike an infrared scan, can be performed during the day. Nuclear testing can also find standing water within the roof system and can read through multiple layers of insulation as far down as 8”. Limitations are the fact that nuclear scans are far more labor intensive and expensive, and the mapping provides anticipated wet areas as opposed to actual locations found with the infrared camera.
Electric capacitance/impedance testing sends an electric current into the roof and is based on the material’s ability to store electrical energy. If there is moisture within the roof system, the dielectric properties will provide higher readings than a dry material would.
Capacitance surveys can be performed with a hand-held device which is normally utilized for confirmation in conjunction with infrared or nuclear scans or on leak investigations for small isolated areas.
A deck scanner can be utilized as a standalone tool for larger projects. As with nuclear surveys, capacitance surveys can identify not only wet insulation, but interply moisture as well as standing water at deck level depending on the roof thickness. Capacitance, when using a deck scanner, does not rely on mapping but can clearly identify areas of moisture that can be marked on the roof.
Capacitance testing is more expensive than infrared testing, but normally less expensive than nuclear testing. Limitations include any membranes that conduct electricity such as EPDM (due to the carbon black within the material) and aluminum coated roofs.
All three methods of non-destructive testing should be confirmed through destructive testing (test cuts) to confirm the equipment is properly calibrated. There are other methods of non-destructive testing; however, they are primarily utilized for leak detection and confirmation of water-tightness of new roof systems, in particular those with overburdens such as vegetative roofs or pavered roof areas.
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