Glossary – N

NECA: National Electrical Contractors Association, Bethesda, MD.


Negative Pertinent Finding: Absence of an exception or a thermal pattern that can be explained by artifacts from construction details or environmental conditions such as shadows and reflections.


NEMA: National Electrical Manufacturers Association, Arlington, VA.


Never Bond: A term used to describe a dry or resin-starved laminate where voids are discovered
between laminate layers due to insufficient wetting of the lamina layers with resin during construction. Newton (N): SI unit of measure for force.


NIST: National Institute of Standards and Technology, Gaithersburg, MD.


Noise Equivalent Temperature Difference (NETD): A measure of the amount of infrared radiation, measured in milliKelvins, required to produce an output signal equivalent to the electronic noise of a particular infrared imaging system. Manufacturers of thermal imaging systems often provide NETD values as a measure of an imager’s thermal sensitivity. Lower values generally indicate better performance.


Non-Destructive Testing (NDT): A method to evaluate the disposition, strength or composition of materials or systems without damaging the object under test. Typically used to evaluate moisture content in roofing assemblies, the three common test methods are electrical capacitance, infrared thermography and nuclear backscatter.


Non-Imaging Radiometer (Infrared Thermometer): An instrument that measures the average apparent surface temperature of an object based upon the object’s radiance.


Non-Veterinarian: A person who is not a Doctor of Veterinary Medicine. NRCA: National Roofing Contractors Association, Washington, D.C.


Nuclear Hydrogen Detection (NHD) Meter: A device that contains a radioactive source to emit high velocity neutrons into a roof system. Reflecting neutrons are measured by a gauge that is used to detect hydrogen; the quantity of hydrogen detected may be linked to the pressure of water.