Testing Building Envelope Systems Using Infrared Thermal Imaging
Introduction
Buildings of all kinds, ranging from houses to factories to high rises, may be troubled by problems related to the design, construction and maintenance that can be difficult to diagnose and resolve. The major problems found in the following buildings:
- Consumption excessive energy due to missing or damaged insulation, insulation performing incorrectly, and excessive air leakage through the thermal perimeter
- The moisture damage from leaks or condensation, especially in walls or roofs
- Ice damage to sloped roofs
- Poor distribution and HVAC performance
- Inadequate verification of construction details or detachment of structural performance of façade materials
- "Sick building syndrome, mold growth and health Other issues
Often the problems – and their causes and their consequences – can not simply not be seen until after costly damage has been done. At this moment the only recourse may be extensive, costly reconstruction. For example, a building Name a nursing home, has had significant problems caused by a poorly designed roof / insulation system ceiling and these included loss excessive heat during the winter months and, therefore, damage extensive ice due to melting snow. Hundreds of thousands of dollars were spent in various attempts, poorly planned to correct the underlying causes. Ultimately the owners simply lived with the problem continued because the corrective actions have been deemed too expensive. Despite this unfortunate resolution, the thermograms helped owners negotiate a financial settlement with the architects and contractors.
When used correctly, imaging Heat allows owners, architects, contractors and inspectors to verify building performance, identify potential problems and validate corrective solutions.
A great value of infrared thermography is that it provides a means of see the invisible thermal signatures related to many of these problems in the building. When properly used, thermography enables owners building, architects, contractors and inspectors to locate problems, verify building performance, and validate solutions. When people act on this information, and significant savings resulting buildings are more comfortable! All surfaces radiate heat invisible. You felt the energy emitted by the sun or a stove burner. The infrared cameras are specially designed electronics that detect thermal radiation. They convert images in this thermal radiation or infrared images which visually describe the temperature differences as small as 0.05 ° C. These portable, battery operated instruments record the thermal data is as always, digital images or conventional video tape or video Digital. The live image is displayed in a viewfinder or an LCD screen. Different temperatures by radiation are represented by different colors or shades of gray. Although it may sometimes be useful to display temperature values, it is often not necessary in construction. Instead, the temperature differences are usually more interesting. Given the right conditions most characteristic of buildings thermal exposure models that can be interpreted by a qualified person. The infrared systems themselves are fairly easy to operate and thus a number of Thermographers conduct building inspections. The task of interpreting the imaging understanding the root causes of problems and solutions are more difficult. Thus, Thermographers often work closely with a team of building scientists, architects and contractors. The key to using thermography is to understand what models successfully associated thermal problems are studied and when those models will be visible in the infrared image.
Building applications for thermography
Thermography has been used since the mid 60s to solve the construction problems. In the late 70s and early 80s, a time when fuel prices rose dramatically, thermography has been widely adopted as a tool to help determine building performance. Since then other applications have been developed and refined, in particular related to the verification of structural performance. The major building-related applications for the technology are detailed below.
Insulation Checks
Missing, damaged or non-performance insulation of they stand out clearly in a thermal image when there are at least 10 ° C (18 ° F) temperature difference is stable from the conditioned space and outdoor air. It is often possible to work with less of a temperature difference due to differences in heat capacity building materials. The inspection is usually done inside and outside. Often, the best results are from from within because of influences fewer but better overall understanding of the building can often be acquired for a larger view altitude outside.
Missing, damaged or non-performance insulation to distinguish clearly in a thermal image when there are at least 10 ° C (18 ° F) temperature difference is stable between space and air conditioning outside.
It is essential to know the type of insulation in the building and construction details, including how insulation has been installed. Insulation may be in place but not performing, often destructive evaluation is warranted to establish basic conditions or understand the exact details of construction. Each type of insulation has a characteristic pattern. A soft foam insulation is likely shrinkage and cracking when installed incorrectly. Many factors impact the image you see. When work is done during the day or early evening, the impact of solar loading must be considered. The affects of the sun can easily last 6-8 hours at a time inside and outside, after a wall was exposed. This often results in the direction of heat flow being reversed, make pictures to confusion and misdiagnosis. Wind must also be reckoned with, as it can both quickly eliminate the thermal difference on a surface and build others. If construction problems are wind-related, ie "we are cold on windy days, then it is wise to do inspection with a wind load. The cost of poor performance of insulation are enormous. In addition to excessive energy consumption, there May be frozen expensive plans water pipes or sprinkler systems, health problems related to growth Mold in colder areas, damage to roofs and interiors caused by ice dams, condensation and water intrusion.
Air Leakage Locations
Excessive air leakage can represent up to half of the energy consumed to condition buildings. Of course, adequate air exchange is essential for occupant health and safety, but most buildings have ever higher rate of air exchange needed. The root cause is often poor design and / or construction permits air to move through the thermal perimeter. Problems can be as simple as a door weather seal failed or as complex as air through a path of continued plumbing in an interior wall or ceiling plenum. The escape route is complex and often without Infrared extremely difficult to visualize. Controls sealing air pipes are better when the air flow is directed and controlled. This can be accomplished with exhaust fans, specialized blower fan, or in large buildings, changing temporary HVAC system, to create negative pressure inside. During the heating season, the resulting sites of infiltration the air seems fresher. The work can be done anytime of the year as long as the temperature difference inside / External is greater by several degrees. Fans blower door can also be used to quantify the rate of air leakage. This technique is very valuable in predicting building performance monitoring of air and water proofing. Most types insulation is not effective to reduce the airflow through the thermal perimeter. Good construction practices include indoor air leakage, if not in an effective manner, air can move through the interior and exterior surfaces and through the insulation. Unfortunately, fiberglass is particularly sensitive to this problem. Thus, if the insulation may be present, it does as expected when the building is in a pressure gradient. This will usually go unnoticed until the fuel bill is paid.
Moisture intrusion or condensation
As the building design and technology production tighter thermal envelopes, moisture (leaks or condensation) has created more problems and more. Water may enter a small crack but is then trapped between the building materials relatively impermeable. Although construction techniques must generally be against both air leakage and moisture retarders to keep moisture from accumulating inside sections of wall. Location moisture thermography is often simple, because water is both a high thermal conductivity and high heat capacity. Determine the source of moisture, however, can be difficult. Condensation, rather than escape, is often the culprit It is therefore important to identify sources of air leakage that can transport moist air into wall sections and cold spots that can result condensation in it. The classic case is that of the warm moist air leaking past the insulation in a metal building or mobile home, as it contacts the cold surface of the metal roof it condenses and freezes frequently, causing occupants to believe, wrongly, that the roof leaks. Building damage due to condensation includes growth of mold, brick spalling, corrosion of roof membrane fasteners and insulation values reduced.
Construction of exterior insulation and coating systems (EIFS)
The growing popularity of buildings using EIFS has been accompanied by numerous cases of moisture related structural damage. Although often attributed to leaky windows, water typically intrudes where sealing or flashing are inadequate or have begun to fail. Moisture is then trapped under the relatively impervious foam. In warm climates the decay of framing timber which can occur very quickly, is a major problem. Mold growth also often accompanies moisture causing health problems. Thermography is a valuable tool to locate moisture in EIFS. Inspections are best conducted in the early evening outside After a sunny day with little or no wind. It may also be possible to locate the humidity inside during cooling or heating conditions. The panels of expanded foam insulation tend to become more absorbing water over time.
Performance HVAC
HVAC systems can be plagued by problems of design and installation that causes overuse of energy and / or buildings uncomfortable. Thermography allows experts to see the otherwise invisible impact of this bad performance as indicated by excessively hot or cold. Once these have been located, the causes can be determined; these may include reversed or bad airflow or misplaced distribution pipes, causing short-circuiting of air directly to the return ducts. Unfortunately, many of these problems are the result of poor design, when one identifies the thermograph, it may be too late to correct. On the other First, some problems (such as broadcasters reverse) are very easy to correct. It is also possible to visualize the airflow itself! Thermography Several studies have been carried out by hanging layers of plastic mesh in a room. As air circulates through it, the temperature compensation can be viewed. In most cases related to comfort, it is probably useful to the image simply walls and objects in the room a technique that is much easier.
Heat sources of basement
Heating coils are used more and more, or to retain outside walkways or ramps free of snow or for heating rooms and hot water or cables. Thermography provides a quick way to verify the location and performance of these devices basement. Typically the thermal model appears very clearly even when the heat source is integrated in several inches of concrete. Similarly, water pipes in the Sections wall can usually be found very easily. Water leaks in pipes, either in a section of wall or under a slab, may also be located using imaging infrared (although the air ultrasound may also be a effective method). To use infrared imaging, temperature difference should usually be induced by running hot water in the pipe. Note that leaks under concrete slabs may not express themselves because the water is drained into the sand / gravel base course and the effects may not be visible from the heat surface. As a side note, Thermographers is often asked to locate reinforcing steel in buildings. This is much more difficult. Heating of steel is not a simple task, usually accomplished with an induction coil or powered directly by DC heating. Secondly, heat is often insufficient to express themselves on the surface. Other methods, based on sending and receiving radio signals, are probably more useful.
Verification Retail Construction
No area of application is more important today, especially in commercial buildings, that verification construction details and performance. Thermography is used with success to verify bond and the placement of stringers in the element concrete masonry (CMU) walls and structural elements of prefabricated, tip-up walls. How? The solid parts of the wall temperature change more slowly than the rest. The inspection can be conducted anytime the wall is in a transient thermal condition – usually early evening as it cools. Because the inspection is done during construction, deficiencies can be corrected prior to occupation of relatively minor inconvenience. Verify placement of insulation in walls of masonry unit shall be larger than in the past because of high costs of energy and health concerns about mold growth in wall cavities Cold.
Sick-Building Syndrome
When buildings are too tight or too wet, health problems quickly come to the forefront. Grouped as "sick building syndrome", they can result in performance inadequate HVAC, moisture trapped in walls, mold growth on cold, damp surfaces and inadequate air rate exchange. Many of them can be visualized and diagnosed, at least in part, by thermography to help solve these very shortcomings serious and common problems. The diagnosis of these problems is often very complex process and, given the fact that litigation may be involved, it is not something taken lightly.
Facade delaminations
Much work has been achieved in South Asia to inspect the facades of buildings for large separations. Failures of these materials can cause serious personnel injury. The masonry tiles used to face buildings tend to change temperature very quickly when they start to take off compared to the underlying structure to which they were affixed. The diurnal cycle is generally the heat source and conduct inspections are done better in the early evening after a hot sunny day.
Roof Moisture Inspections
The inspection of flat roofs, especially roof (BUR) has been proven for a number of years. The technique allows detection of moisture in a roof system, over time this moisture leads to pre-mature deterioration of the roof. Moisture seems warmer in the evening after a sunny day because of its higher thermal capacity. The roof surface must be dry and the technique works best on roofs with absorbent insulation. The inspection work may be done either in a survey on the roof top or in an aerial survey made from a helicopter or fixed wing craft.
Standards and references
Several important standards that exist to support the work of Thermographers perform inspections of the building. These include, among others, the following:
- ASTM C 1060-97 – Practice for Thermographic Inspection of isolation facilities in cavities Envelopes Frame
- ASTM C-1153-97 – Convenient location of Wet insulation in roofing systems using infrared imaging
- ISO 6781 – Thermal insulation, detection qualitative thermal irregularities in building envelopes, Infrared Method
- American Concrete Institute Standard 530 Design / American Society of Civil Engineers Standard 5, Building Code Masonry and specification
Another excellent reference, but not a standard, is the Canadian General Standards Board Manual thermographic analysis of the building envelope (149-GP-2MP). Many building Documents Related were published over the years, many are collected on a CD-ROM from SPIE, entitled Selected Papers from the Proceedings of Thermosense, edited by John Snell and Doug Burleigh, available to the United SPIE.
Conclusion
When is properly used by skilled people, technology, thermal imaging can play a powerful role in the visualization of construction problems otherwise invisible conditions. Contractors and architects are both using thermography to ensure the performance of their buildings. Building Effective on thermography specialists to help them diagnose difficult problems that, left unresolved, are costly or dangerous. Owners rely on thermography as a tool for controlling a new building. Even if a foundation of expertise should underpin the successful use thermography for building diagnostics, start with most applications, is often not difficult. A suitable infrared system is required, with a adequate training and experience of the operator as well. Having additional knowledge of Building Sciences or access to this Information is also essential. The primary return on an investment in building thermography is gaining a higher level of buildings insurance will work as expected, and the occupants are more comfortable, often at lower cost.
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