Infrared thermography
Images courtesy IR Analyzers/Vector Mapping
The infrared thermography method uses infrared imaging to identify temperature differentials between dry and wet locations to indicate the presence of water in the system. This method operates on the principle wet insulation has a higher thermal mass and, therefore, retains heat longer than dry insulation. Although this method is not time consuming and allows the operator to sample the entire roof, it can provide misleading information. Since the testing relies on differences in temperature, mechanical equipment, heating/cooling systems, and shaded areas can adversely influence the results.
Infrared imaging per ASTM C1153, Standard Practice for Location of Wet Insulation in Roofing Systems Using Infrared Imaging, and Testing Application Standard (TAS) 126-95, Standard Procedures for Roof Moisture Surveys, is used to determine the location of wet insulation in contact with the membrane in the roofing system. This test method is often used at night when the roof begins to cool because the wet insulation (higher mass) retains heat longer than the dry area (lower mass). The infrared camera is able to capture the temperature differential between the dry and wet roof areas.
Unlike electronic leak detection, infrared thermography is unable to identify the source of the leak. However, moisture content can be measured using core samples.
Infrared thermography can be specified to analyze the presence of moisture in all types of roof membranes. However, it is incompatible with ballasted roof assemblies or PMR/IRMA varities. During testing, the membrane must be dry and devoid of condensation. This test method is not suitable on insulations that do not absorb water, such as expanded polystyrene (EPS) and closed-cell sprayed polyurethane foam (SPF). Additionally, infrared thermography should not be specified when the existing roof deck is capable of retaining significant amounts of water. These wet-applied decks include lightweight concrete and poured gypsum.
Similar to other methods of moisture detection, infrared thermography can generate false positives, and the operator’s experience is important for interpreting results accurately.
| INCREASING RESILIENCY OF ROOFING SYSTEMS |
| The federal government has initiated a mandate to increase the resiliency of the built environment through the Climate Resilient Buildings and Core Public Infrastructure project at the National Research Council Canada (NRC). The initiative includes two major projects relevant to the roofing industry.
The Guidelines for Commissioning and Certifying the Resiliency of Roofs Subjected to Extreme Weather Events project involves developing field protocols to perform in-situ assessments of wind uplift resistance, watertightness, and thermal performance. These tools will allow the industry to assess the capacity of a new roof, ensuring it was installed to meet the design requirements and withstand climatic events. The guidelines will also provide the industry with a method of assessing the remaining roof capacity after either an extreme event or field aging. The Codification of Material Properties for Building Adaptation to Climate Change project includes evaluation of the properties of more than 20 common building materials for various climatic zones to develop a database of climate-dependent material properties. One of the major outcomes of this initiative is the development of an online database tool to improve access and ease of use for the building envelope community. Both NRC projects are aimed at increasing the resilience of the building envelope and roofing. These initiatives were identified through an industry consultation on building resiliency held in 2016. The methodologies derived from the climate adaptation projects are scheduled for inclusion in the National Building Code of Canada (NBC). |
