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Application Notes:
Moisture in Building Envelopes |
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The presence of moisture in building envelopes, whether from leakage or condensation, can have serious consequences. For example, moisture in insulation reduces its insulating capability, causing heating and/or cooling losses and wasting energy. Moisture can also cause structural deterioration and foster the growth of mold, while a serious roof leak can damage or destroy a building's contents.
Thermography, also known as thermal imaging, is well suited to identifying wet spots in building envelopes. As a diagnostic technique, thermography captures two-dimensional images of the apparent temperatures of equipment and structures. Thermal images can reveal anomalies in roofs and walls that can indicate the presence of moisture as buildings cool after having been under a thermal load. This happens because water conducts and stores heat better than most building materials. So, when a roof or wall cools, wet or damp areas cool slower than dry areas and show up as "hot spots" on thermal images.
The following discussion focuses on using thermal or infrared (IR) imaging to check for moisture in the envelopes of Moisture in building envelopes For more information on Thermal Imagers go to www.fluke.com/thermography Application Note Applications for Thermal Imagers industrial, commercial and institutional buildings, including moisture in roofs, walls and insulation.
What to check?Check the outside walls and roofs of buildings after they have experienced a thermal load, e.g. a solar load on a hot, dry day. Eastfacing walls might be checked in the afternoon and (in the Northern Hemisphere) south- and west-facing walls and roofs after sundown. A significant thermal gradient (15 or 20 %) between the inside and outside is essential in order detect thermal anomalies attributable to the difference in heat capacity between the materials of construction and the additional moisture load.
When potential wet spots in exterior walls and roofs are identified, follow up with an inspection inside the building, to further refine the outdoor findings. Inside inspections can also independently pinpoint moisture in ceilings and walls caused by leaks, water pipe breaks, firesprinkler discharges or other water-producing events. Fast action with a thermal imager following a water-producing accident can identify which materials must be dried or replaced.
What to look for?Collecting thermal images is a good first step in analyzing a structure and identifying suspected problem areas. Unlike other moisture-detecting technologies, such as meters, thermography requires no physical contact with roofs, ceilings, walls or floors. In addition, you can check inaccessible areas and cover a large area in a single image.
Regular building-envelope inspections are key to prolonging the lives of industrial, commercial and institutional buildings. New construction and especially new roofs should by thoroughly inspected 6 to 9 months after construction, while the structure is still under warranty. That time lag allows the structure to experience the elements, hopefully a rainy season. Then, perform additional building-envelope scans every two to five years. Compare them to the original, baseline images to establish trends and determine remedies to any deterioration. Experts estimate that preventive maintenance of this kind will double the life your facility's roof. Roof inspections should be conducted with the imager mounted on a tripod, so that the technician can concentrate on properly adjusting the camera to maximize the thermal resolution and analyzing the image.
Fluke thermal imagers now include IR-Fusion®*, a technology that fuses a visual, or visible light, image with an infrared image for better identification, analysis and image management. The dual images are accurately aligned at any distance heightening details, making it much easier to spot where further investigation is needed.
What represents a "red alert"?Give any building-envelope condition that poses a safety or health risk the highest repair priority. Next, any roof leaks or moisture conditions that threaten production, electronic data, electronic equipment or the integrity of the building itself should receive immediate attention.
What's the potential cost of failure?Flat roofs are the parts of commercial, industrial and institutional buildings that are the most likely to fail, and they are expensive to replace. Factors vary so much from facility to facility that it's difficult to put a price on roof replacements, but one expert writing in 1989 came up with a range of weighted averages between $4.50 per square foot for mechanically attached singleply roofs and $8.00 per square foot for coal-tar built-up roofs.*
Follow-up actionsBefore checking your building for moisture, be aware that this kind of inspection constitutes one of the most challenging ...
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