infrared camera design engineer
Testing Building Envelope Systems Using Infrared Thermal Imaging
Introduction
Buildings all types of houses to factories to high rises, can suffer from problems related to design, construction and maintenance that can be difficult to diagnose and resolve. The major problems found in buildings include:
- Excessive use of energy due to missing or damaged insulation, insulation inadequate performance, and excessive air leakage into the surrounding thermal
- Moisture damage caused by leaks or condensation, especially in walls or roofs
- Ice damage to pitched roofs
- Poor performance or HVAC distribution
- Inadequate monitoring of construction details and structural performance of delaminations facade materials
- "Sick Building Syndrome," mold growth and other issues related to health
Often the problems - and their causes and consequences - Simply can not be seen only after serious damage is done. At that point only one appeal may be extended, costly reconstruction. For example a commercial building, a nursing home, had major problems caused by a poorly designed roof / ceiling insulation system, which included excessive heat loss during the winter months and as a result, extensive ice damage result of snow melt. Hundreds of thousands of U.S. dollars were spent in various poorly planned attempts to correct the underlying causes. At the end of the owners lived just with the continuing problem because corrective actions were deemed too expensive. Despite this unfortunate resolution, the thermo grams helped the owners to negotiate a financial settlement with the architects and contractors.
When used properly, thermal imaging allows builders, architects, contractors and inspectors verify building performance, potential problem areas to identify and validate corrective solutions.
A great value of infrared thermography is that one way of seeing the invisible thermal signatures on many of these problems in the building. When properly used, thermography can building owners, architects, contractors and inspectors to locate problems, verify building performance, and validate solutions. When people act on this information, significant savings rise buildings and comfortable! All surfaces radiate invisible heat energy. You've felt this energy radiated by the sun or a stove burner. Infrared Cameras are specially designed electronic devices that detect thermal radiation. They convert this thermal radiation into images, or thermo grams, which visually portray temperature as small as 0.05 ° C. This portable, battery-operated instruments record the thermal data either as still, digital images or conventional videotape or digital video. The image is displayed live in a viewfinder or an LCD screen. Different radiant temperatures are displayed as different colors or shades of gray. Although sometimes it useful to display the temperature values, it is often necessary in building work. On the contrary, the temperature differences are usually the most interesting. Given the right Most buildings thermal conditions exhibit characteristic patterns that can be interpreted by a qualified person. The infrared systems themselves are fairly easy to operate and thus a number of buildings conduct thermographic inspections. The task of interpreting the images, understanding the cause of problems and finding solutions are all difficult. This thermographic often work closely with a team of building professionals, architects and contractors. The key to successful use of thermography to understand what thermal patterns associated with the issues under study and know where those patterns are visible in the infrared image.
Building Applications Thermography for
Thermography has been used since the mid-60s building to solve problems. During the late 70s and early years '80, When a fuel rose dramatically, thermography has been widely embraced as a tool to determine building performance. Since then other applications developed and refined, with particular regard to the verification of structural performance. The main building-related applications for the technology below.
Insulation Checks
Missing, damaged or non-insulation will perform are clearly in a thermal image when there are at least 10 ° C (18 ° F) temperature difference between the stable and the air conditioned space. It is often possible to do work with a temperature of less widespread due differences in the thermal capacity of building materials. The inspection is usually done both inside and outside. Often the best results are obtained from within due less influence, but a better understanding of the total of the building can often be gained from greater views of the exterior elevations.
Missing, damaged or non-performing insulation will assist in a clear thermal image when there are at least 10 ° C (18 ° F) temperature difference between the stable conditioned space and the atmosphere.
It is essential to the nature of the insulation in the building and construction details, including how the insulation was Installed know. Isolation may be in place but not performing, often destructive evaluation is warranted to baseline conditions to determine whether the precise structure understand detail. Any type of thermal insulation has a characteristic pattern. A soft foam insulation is susceptible to shrinkage and cracking in poorly installed. Many factors impact of the image you see. When the work is done in the daytime or early evening, the influence of solar - loading must be considered. The influence of the sun can easily last 6-8 hours on both the inner and outer wall after one is exposed. This often results in the direction of heat flow is reversed, for disturbing images and misdiagnosis. Wind should also be reckoned with as it can easily skim the thermal difference on a surface lift and others to improve. If wind-related building problems, that is, "We are cold on windy days, "it is wise to carry out the inspection with a wind load. The cost of the poor performance of the insulation are enormous. In addition to high energy consumption, can costly freeze-ups of water or fire sprinkler systems, health issues related to mold growth in cold places, damage to roofs and interiors caused by ice dams, condensation and water intrusion.
Air Leak Location
Excessive air leakage can account for more than half the energy consumed by the condition of buildings. Of course adequate air exchange is essential for the health and safety of the residents, but most buildings have a much higher rate of air exchange than needed. The cause is often poor design and / or construction that allows air to move about the thermal circumference. The problems can be as simple as a failed door seal or as complex as an air route through a plumbing chase in an interior wall or ceiling plenum. The leakage pathway is often complex and not infrared, very difficult to visualize. Air leakage inspections are best performed when the airflow is directed and controlled. This may be achieved with exhaust fans, fan blower door specialist, or, in larger buildings, temporary modification of the HVAC system, a negative pressure in it. During the heating season the resulting sites of air infiltration appear cooler. The work can be done any time of year as long as the indoor / outdoor temperature difference is greater than a few degrees. Blower Door fans can also be used to quantify air leakage. This technique is invaluable in predicting building performance monitoring and air sealing work. Most types of insulation are not effective in reducing air movement through the thermal perimeter. Good construction practice includes interior air sealing; if not place effectively, the air moving through the interior and exterior surfaces and through the insulation. Unfortunately fiber is particularly sensitive to this problem. So, while the present isolation may be, is not performing as expected when the building is under a pressure gradient. This will usually go undetected until the fuel bill is paid.
Moisture intrusion or condensation
As building designs and techniques produce tighter thermal envelopes, moisture (leaks or condensation) has more and more problems. The water can penetrate through a small crack, but it is then trapped between the relatively impermeable materials. Well construction techniques usually involves both air sealing and moisture retarders to keep moisture from accumulating in the wall sections. Locating moisture with thermography is often simple, because water has both a high thermal conductivity and high heat capacity. Determining the source of the fluid, can be difficult. Condensing, rather than leakage, it is often the culprit so it is important sources of air leakage that moist air transport in the wall sections and the cold spots that can result in the identification condensing. The classic case is that warm moist air leaking through the insulation in a metal building or mobile home, because the cold underside of the metal roof condenses the contacts, and often freezes, making the residents of thought, wrongly, that the roof is leaking. Building damage caused by condensation include mildew growth, Spalling brick, roof membrane closure corrosion and reduced isolation values.
Construction of Exterior Insulation and Finish Systems (Eifs)
The growing popularity of buildings EIFS was accompanied by numerous cases of moisture in relation to structural damage. Although often attributed to leaky windows, water typically enters where sealing or flashing systems were inadequate or have begun to fail. Moisture is then trapped below the relatively impervious foam. In warm climates the decay of the wooden structural elements, which can very rapid action, is a major problem. Mold growth often accompanies the fluid results in health. Thermography is a valuable tool to locate moisture in EIFS. Inspections are best conducted in the early evening of the outside world after a sunny day with little or no wind. It may also be possible to locate moisture in during the cooling or heating conditions. The expanded foams tend to absorb water over time.
HVAC Performance
HVAC systems can be plagued by the design and installation problems that lead to excessive use of energy and / or uncomfortable buildings. Thermography helps building specialists visualize the otherwise invisible impact of this poor performance as indicated by excessively hot or cold. Once these are located, the underlying causes are determined, this can be reversed or misdirected or poorly placed supply air ducts, leading to short circuiting directly to the return air ducts. Unfortunately many of these problems are a result of poor design, by the time a thermographer identifies them, may be too late to correct. On the other hand, some problems (such as reverse Diffusers) very easy to correct. It is also possible to visualize the air flow itself! Thermography Several studies carried out by hanging layers of plastic mesh in a room. As the air flows through it, the temperature of the netting can be displayed. In most comfort-related cases, it is probably useful to just the image of the walls and objects in the room a technique that is much easier.
Soil heat sources
Heating coils be used more and more to keep, or sidewalks or driveways outside entrance free of snow or heat to provide spaces and rooms with hot water or electric wires. Thermography offers a quick way to check the location and performance of these devices underground. Typically the thermal pattern appears very clearly, even when the heat source is embedded in several centimeters of concrete. Also water pipes in wall sections can usually quite easily be established. Water leaks in pipes, or in a wall unit or under a sheet, may also be placed by infrared imaging (ultrasound, although the air also an effective method). The use of infrared imaging, a temperature difference is usually caused by running hot water through the pipe. Note that leaks under concrete slabs can not express themselves, because the water drained away in the sand / gravel base layer and the thermal effects are not visible from the surface. As an aside, are often asked to locate thermal reinforcing steel in buildings. This is much harder. Heating of steel is no easy task, usually performed with an inductive coil or direct DC-powered heating. Second, heat often insufficient to on the surface. Other methods, based on sending and receiving radio signals, are probably more useful.
Verification Construction Detail
No area of application is important that days, especially in commercial buildings, then the construction details and performance verification. Thermography is used with great success to verify bond beams and placement of reinforcement in concrete masonry unit (CMU) walls as structural elements of pre-cast, tip-up walls. How? The fixed parts of the walls change temperature more slowly than the rest. The inspection can any time carried into the thermal wall is a temporary condition - usually in the early evening when it cools. Because the inspection is performed during construction, deficiencies may prior to the occupation with a relatively minor inconvenience corrected. Verification of the placement of the insulation in masonry walls is more important than unity in the past due of high energy and health concerns about the growth of mold in cold cavity walls.
Sick building syndrome
If too tight or too damp buildings, health-related problems quickly come to the fore. Grouped as "Sick Building Syndrome", which may result from inadequate HVAC performance, moisture trapped in walls, fungus growing on cold, damp surfaces and inadequate air change rates. Many of these can be visualized and diagnosed, at least in part, with thermography to help solve this serious and common problems. Diagnosis of these problems is often a very complex process and, given the fact that disputes may be involved, it is not something to be incorporated into light.
Facade Delaminations
A large Part of the work is done in Southeast Asia, the inspection of the facades of large buildings for delaminations. Malfunctions of these materials can cause serious personnel injury. The masonry tiles used to face buildings tend to change quite rapidly when temperatures begin to delaminate over the underlying structure on which they were made. The daily cycle is usually the driving heat source and inspections are best done in the early evening hours after a warm sunny day.
Roof Moisture Inspections
The inspection of flat roofs, especially urban roofs (BUR) is proven for a number of years. The technique allows for the detection of moisture trapped in a roof system over time moisture leads to the pre-mature deterioration of the roof. The moisture seems warmer at night after a sunny day because of the increased thermal capacity. It roof surface is dry and the technique works best on roofs absorbing insulation. Inspection work can be achieved in a survey or a roof from a helicopter aerial survey or fixed wing craft.
Standards and References
Several important standards exist to support the work of conducting thermographic building inspections. These include the following:
- ASTM C 1060-97 - Practice for Thermographic Inspection of Insulation Installations in Envelope cavity of Frame Buildings
- ASTM C-1153-97 - Practice for the location of the Wet Insulation in Roofing Systems Using Infrared Imaging
- ISO 6781 - Thermal insulation, qualitative detection of thermal irregularities in building envelopes, Infrared Method
- American Concrete Institute Standard 530 Design / American Society of Civil Engineers Standard 5, masonry Building Code specification
Another excellent reference, although not a standard, the Canadian General Standards Board Guide for the thermal analysis of building enclosures (149-GP-2MP). Many building-related documents published over the years, many are gathered on one CD-ROM from SPIE, entitled Selected Papers of the Proceedings of Thermo Sense, published by John Snell and Doug Burleigh, available of SPIE organization.
Conclusion
When properly used by qualified persons, to thermal imaging technologies play an important role in visualizing otherwise invisible problems and building conditions. Contractors and architects are both using thermography to ensure the performance of their buildings. Building thermography specialists rely on to help them diagnose tough issues, left unresolved, are costly or dangerous. Owners trust on thermography as a tool for the commissioning of a new building. While a foundation of the expertise of the successful use of thermography for building diagnostics at must underpin, to work with most of the applications is often difficult. An appropriate infrared system is needed, with proper training and experience for the operator too. After additional knowledge of building sciences or access to that information is also vital. The primary return on an investment in building thermography is gaining a higher degree security of buildings will perform as intended and will be more comfortable occupants often at a lower cost.
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