The defects of building envelope structure are mainly divided into surface surface thermal defects and internal surface thermal defects, including thermal bridge defects, ring beams, columns, corners, etc., which are weak parts of the thermal function of the building's outer protective structure, which affects the building. An important factor in energy saving effects and building thermal comfort. Most of these wall thermal defects are concealed. Engineering data and conventional on-site inspection methods are not sufficient to determine the location and severity of the site, and then affect the evaluation of building thermal power and energy efficiency. The infrared thermal imager can be used to quickly and comprehensively identify the thermal conditions of the building and find out the parts with thermal defects, which have the effect of looking at the overall situation. Therefore, prior to the detailed inspection of the building envelope structure, it is advisable to prioritize the inspection of building thermal defects.

A. The concept of thermal bridge

• Thermal bridge means: some parts of the building envelope structure, under the effect of temperature difference in the chamber surface, constitute the area where the heat flow is relatively full and the inner surface temperature is low. These parts become bridges with a lot of heat transfer, so they are called thermal bridges . Sometimes they are called cold bridges. The reason is that the part where this phenomenon occurs can always feel the presence of cool air. low.

• Heat is an energy. The conduction of heat energy requires a route and a bridge. Those parts with low thermal resistance and large heat transfer coefficient supply heat-conducting bridges. Therefore, these parts are called “ heat bridges ” . The terminology used in the Building Thermal Design Standard ( GB50176-93 ) is “ Thermal Bridge ” .

• Thermal bridges are often caused by the fact that the heat transfer coefficient of this part is much larger than that of adjacent parts and the insulation function is much worse. This is a very common phenomenon in the envelope structure. For example, metal, concrete or reinforced concrete beams, columns, slabs and ribs built in brick walls or aerated concrete walls, ribs in prefabricated insulation, and metal joints in the sandwich insulation wall for the two walls in the splicing table a metal anchor for the fixed insulation board in the external thermal insulation wall, a keel provided in the inner insulation layer, a joint part of the selected balcony board and the main structure, a door and window frame in the heat preservation door and window, especially a metal door and window frame, etc. Wait.

• In the cold season, the heat dissipation area of ​​the corner of the outer wall is larger than that of the heat absorption area. The air flow rate in the corner is slower. The heat in the room is less than the adjacent flat part. It is also the hot bridge where the heat flow is full and the inner surface temperature is low.

• Due to the low temperature of the inner surface of the thermal bridge, during the winter, when the temperature is lower than the dew point, water vapor will agglomerate on the surface to form condensation.

2. Application category

Infrared thermal imaging cameras are used more and more widely, and are often used in building construction for building thermal defect detection; building air tightness testing; moisture leak detection; building energy auditing; heating systems and pipelines, electrical equipment protection and defects Detection, etc. The infrared camera relies on its simple and high-power detection method, which has gradually become a powerful test for engineers.

1. Building thermal defect detection to ensure building quality

Using a thermal imager to detect and analyze structural defects is a quick and useful method. A clear heat map can provide you with detailed building thermal information. You can clearly see the building's heat loss, moisture and building gas. In the case of tightness, in addition to this, you may use this information to summarize the insulation effect of the building and check whether the building is at risk of defects, and this information is supplied by infrared camera-non-destructive testing method!

2. Find the location of the roof leakage

Finding a roof leak is a typical application of infrared cameras in building inspection. Long-term buildings in the year, the sun, the rain and the erosion of the atmosphere, the building is extremely vulnerable, the damage will cause the effect of heat insulation or heat preservation to fall, and rainwater leakage and other problems occur. Severe circumstances will affect people's lives. With excellent thermal sensitivity, the infrared camera can clearly show the slender temperature difference, find and locate the leak point, and ensure the building quality.

3, building energy audit review

In building inspection, the infrared detection method is a method for measuring the rapid evaluation of building energy consumption. The thermal imaging camera has excellent thermal sensitivity and provides a clear infrared image for analysis of building insulation loss, thermal and thermal bridge defects. The infrared camera can fully reflect the loss of building energy consumption due to external walls or doors and windows, the situation of the radiator and the detection of the external wall of the building. The infrared camera can supply a high-resolution heat map and is an aspiration for building exterior wall inspection and protection.

4. Detecting the equipment and work of the heating system

The thermal imaging camera provides intuitive and convenient operation to quickly and safely detect the equipment and operation of the air conditioning ventilation system. The infrared camera can clearly show the distribution of the temperature field, and the temperature distribution can be found at a glance, which can be used for the work review of the air conditioning ventilation system. In addition, the short-term method of infrared camera supply is used to detect the presence of siltation and blockage of the radiator.

5. Check and measure the operation of the solar system

The purpose of checking and measuring the operation of the solar system is to ensure that the system is safe and useful. The solar system works completely in the light of the sun. A defective light-sensing unit not only jeopardizes the function of the system, but also causes system defects, and then a large amount of heat energy occurs, posing a risk of fire defects. Thermal imagers are used in solar system testing to detect potential fire risks and the risk of defects affecting system operation, to greatly protect system safety and to ensure personnel safety.

6. Pipe inspection, whether there are leaks and cracks

The general way to check for defects in the pipeline is to uncover the entire wall or the ground and perform a thorough inspection. This is an amazing and costly method of damage. The infrared thermal rubber meter can supply a non-destructive test and a targeted detection method to make the damage small and cost-saving. For example, to detect the leakage of water pipes in the floor heating system, the infrared thermal imager can accurately locate the leak points and repair them by measuring the heat distribution on the surface of the ground through the principle of heat transfer. Do not need to damage the defect-free parts, make the repair more power and specific, and then save the repair cost and time.

7. Moisture leakage detection

In the building, not only the water pipe rupture will cause the wall to be wet. Because the erosion of the atmosphere will damage the structure of the building, these defective structures are prone to rain leakage problems. If the water cannot be boring in time, then Moisture builds up in the walls. The thermal imager can clearly map the distribution of the surface moisture of the building, find the high-humidity risk area, and investigate the cause to avoid the harm of a larger area.

8. Mildew risk detection

Building cold bridges can lead to energy loss. In these areas, such as high humidity in the air, it is easy to integrate water, which will cause mildew. The occurrence of mildew will not only damage the quality of the building, but also affect the health of the residents. The infrared camera provides the surface moisture imaging function of the building, clearly reveals the high temperature area, and quickly and easily finds the risk of mold.

9. Building air tightness testing

In short, if the building doors and windows do not have the correct equipment, in the winter, the cool air will be poured, and the heating leakage will occur. As a result, the heating system load will increase and the working cost will be added. This problem is called “ building gas”. Confidentiality " defect. The so-called " building energy saving " generally refers to the airtightness test of the building, and the cause of the sealing problem may be caused by the quality of the insulation layer, the quality of the construction or the aging during the construction process, and the problems that lead to the leakage are found. It is the key to reducing energy loss. The function of infrared thermal imaging is to find the airtight defect parts agilely. Through the pressure test, check the key parts such as doors, windows and pipes, find the leak points agilely, supply useful qualitative analysis basis, find the problem location area, and make it simple and clear. .

10. Large-scale building panorama analysis

When using a thermal imaging camera to photograph large buildings, photography can only be partially performed due to the limitations of the photographic space. Infrared thermal imager's new picture stitching function, using the panoramic stitching helper to stitch several pictures into a panoramic heat map, without affecting the clarity of the pictures and the photographic data. Panoramic analysis of the entire building makes it easy to spot thermal defects.