Building energy-saving detection is a technical operation related to the thermal performance of raw materials, equipment, facilities and buildings used in energy-saving buildings by professional technicians using standard methods, suitable instruments and equipment and environmental conditions. Let's learn about energy-saving quality inspection of construction projects!

First, the concept of detection

It is an important means to ensure the construction quality of energy-saving buildings. The quality inspection of building energy-saving projects is divided into two parts: laboratory inspection and on-site inspection. Laboratory testing means that samples are processed in the laboratory and relevant testing parameters are measured in the laboratory; On-site detection refers to the measurement of relevant detection parameters of the test object or specimen at the construction site.

Second, the significance of detection

Building energy efficiency refers to the implementation of energy-saving standards, the use of energy-saving technologies, processes, equipment, materials and products in the planning, design, new construction (reconstruction and expansion), transformation and use of buildings, the improvement of thermal insulation performance and the efficiency of heating, air conditioning, refrigeration and heating systems, the strengthening of the operation and management of building energy systems, the use of renewable energy, the reduction of heating, air conditioning, refrigeration and heating, and the reduction of indoor thermal environment quality. Simply put, building energy conservation means "reducing the energy loss in the building" and "improving the energy utilization rate in the building". China's building energy-saving work began in 1980s, and 1993 formulated GB50 176 Code for Thermal Design of Civil Buildings. With the rapid development of the national economy and the rapid expansion of the construction industry, new buildings not only consume a lot of energy in the construction process, but also continue to consume a lot of energy in the long-term use process, and the building energy consumption has accounted for 1 /3 of the national total energy consumption. Since 2000, the state has strengthened the work of building energy conservation nationwide. A series of building energy-saving standards, regulations and norms have been formulated. It should be said that as long as we start from the leading work of building energy-saving design, we should select and use energy-saving materials and products in strict accordance with building energy-saving design standards; In the process of energy-saving project construction, the construction of energy-saving materials and product systems can be well controlled, and the energy-saving performance of completed buildings can be fully guaranteed. However, this is not the case. Especially in hot summer and cold winter areas, most designers lack knowledge of building energy efficiency, and their understanding of new building energy efficiency codes and standards needs to be improved. At the same time, the construction period is long and there are many energy-saving construction links; Builders and developers do not know enough about the importance of building energy efficiency, and often deviate from the design and standards in construction; Coupled with the drive of interests and the infiltration of bad social atmosphere, it is inevitable to cut corners. In view of the above phenomenon, in order to ensure the quality of building energy-saving projects, it is necessary to supervise the quality of building energy-saving construction through relevant testing. The National Building Energy Efficiency Quality Supervision and Inspection Center can accept the entrustment of building energy efficiency testing and carry out building system evaluation.

Third, the detection classification

1, laboratory and field tests

Like the quality inspection of conventional building projects, the inspection of building energy-saving projects is divided into two parts: laboratory inspection and on-site inspection. Laboratory testing means that samples are processed in the laboratory and relevant testing parameters are measured in the laboratory; On-site detection refers to the measurement of relevant detection parameters of the test object or specimen at the construction site.

2. Type inspection and sampling inspection

From the construction quality control process of building energy-saving projects, building energy-saving detection can be divided into type detection of components, thermal insulation and energy-saving systems and components (referred to as type detection), on-site sampling re-inspection detection (referred to as re-inspection detection) and on-site supervision and inspection detection (referred to as supervision detection). Type test is a necessary condition for building energy-saving components, materials, thermal insulation and energy-saving systems to enter the construction site. Enterprises entering the construction site should have an effective type test report with complete test parameters. Due to the large amount of building energy-saving components used in construction projects, most of the on-site construction personnel are not well educated, unfamiliar with new building energy-saving new products and systems, and lack of relevant practical experience, it is necessary to review the sampling of building energy-saving components and components of thermal insulation and energy-saving systems. Due to the short promotion time of building energy-saving work, the understanding of building energy-saving technology and energy system products by relevant personnel at all levels of building engineering design, construction and supply generally needs to be improved. During this period, it is particularly important to strengthen the publicity and training of energy conservation and the supervision of the government and its functional departments. Regular and irregular supervision and inspection by the government and its functional departments in the process of building energy-saving construction can correct the defects in the design process in time, prevent fake and shoddy "energy-saving products" from mixing into the construction site and avoid making "tofu residue" projects.

Fourth, the content of the exam

Building energy-saving testing content includes:

1, material properties (thermal conductivity, density, moisture content) of the main components of the thermal insulation system;

2. Performance of external wall insulation system (heat transfer coefficient, weather resistance, wind load resistance, impact resistance, bond strength, on-site physical inspection of external wall energy-saving structure);

3. Energy-saving detection of heating residential buildings (indoor and outdoor average temperature detection, heat transfer coefficient of envelope, internal surface temperature of thermal bridge, unit heat consumption of building, thermal defects);

4, building doors and windows (air tightness, thermal insulation performance);

5, heating and air conditioning system energy-saving project (indoor temperature, relative humidity, water pressure, wind pressure, air volume, wind speed, hydraulic balance, water replenishment rate, heat transfer efficiency, air conditioning unit water flow, total hot and cold water flow, total cooling water flow);

6 power distribution and lighting energy-saving projects (average temperature, lighting power density, low-voltage distribution power supply, speed);

7. Monitoring and control of energy-saving projects (monitoring and control of energy-saving projects);

8, insulating glass (dew point);

9. Anchor bolt (pull-out test of anchor force on site).

The main instruments and equipment include thermal conductivity tester, infrared camera, external wall weatherability tester, wire drawing tester, thermal insulation system tester, door and window air tightness test system, explosion-proof door air tightness test system (building air tightness test system), dust particle counter and so on.

Verb (abbreviation of verb) detection method

1. Energy-saving detection of external wall insulation system mainly includes system weather resistance test, system wind load resistance test, system impact resistance test, tensile strength test and heat transfer coefficient measurement test. In the current building energy-saving detection, the main technology is to quickly and accurately measure the thermal performance of the building envelope, that is, the heat transfer coefficient of the envelope. There are two main methods to measure heat transfer coefficient: heat flow meter method and hot box method. Heat flow meter is a commonly used instrument in building heat consumption measurement. The basic principle of its detection is that at least two heat flow meters are arranged at the tested part to measure the heat passing through the building components, and four thermocouples are arranged around the heat flow meters and on the corresponding cold surfaces to measure the temperature, which is directly transmitted to the microcomputer system, and the heat transfer coefficient value is obtained through calculation. The working principle of hot box method is to establish the required temperature, wind speed and radiation conditions in the boxes (cold box and hot box) on both sides of the specimen. After reaching the steady state, the heat transfer performance of the sample can be calculated by measuring the air temperature, the surface temperature of the sample, the temperature of the inner wall of the box and the power input into the metering box. Hot box method is not suitable for on-site detection, but suitable for laboratory measurement of heat transfer coefficient of external walls, floors, doors and windows. At present, the more advanced method is infrared thermal imager method. Infrared thermal imager is a high-tech product integrating advanced photoelectric technology, infrared detector technology and infrared image processing technology. Thermal imager is a non-contact instrument to measure the surface temperature of an object quickly, which can directly display the temperature distribution range of the object surface. In addition, there are many display modes, large output information, data processing, simple operation and convenient carrying.

2. Detection of building exterior doors and windows The energy-saving detection of building exterior doors and windows mainly includes the detection of heat preservation and air tightness. Doors and windows are the components with the weakest thermal performance in building envelope, and the energy consumption through doors and windows accounts for a considerable proportion of the whole building energy consumption. The investigation shows that because ordinary steel doors and windows are used in heating buildings in some parts of northern China, the sum of heat transfer and air permeability of external windows in winter can reach more than 50% of the total energy consumption of buildings. In summer, the heat gained by solar radiation entering the room through sunny doors and windows becomes the main body of air load. Evaluation of thermal insulation performance of exterior doors and windows by heat transfer coefficient. The detection method is calibration hot box method. One side of the specimen is a hot box to simulate the indoor climate conditions of heating buildings in winter, and the other side is a cold box to simulate the outdoor climate conditions in winter. Under the condition that the gap of the specimen is sealed and the air temperature, airflow speed and thermal radiation on both sides of the specimen remain stable, the heat loss through the outer wall of the hot box and the frame of the specimen is subtracted and divided by the product of the area of the specimen and the air temperature difference on both sides, and the heat transfer coefficient of the specimen can be obtained. Generally, the pressure method can be used to detect the air tightness of external doors and windows, that is, the pressure difference between the inside and outside of external doors and windows of buildings is artificially created by using the principle of pressurization or decompression such as fans, and the air permeability under this pressure difference is measured.

Six, detection technology

China's building energy-saving detection technology and building energy-saving work develop simultaneously, which can be divided into two categories: direct detection and indirect detection. Direct detection is the method of energy measurement, that is, providing heat source to the detected building unit, and after it is stable, testing indoor and outdoor temperatures and measuring the total supply of heat source. According to the building area, the measured indoor and outdoor air temperature difference and the measured energy consumption, the unit heat consumption of the building is calculated under the temperature difference specified in the standard. The indirect method is to calculate the heat consumption of the building by testing the heat transfer coefficient and air tightness of the building envelope. Testing the heat transfer coefficient of envelope is usually to try to form a relatively stable temperature field on both sides of the measured structure, and to test the heat flow through the measured structure under the action of this temperature field, so as to get the heat transfer coefficient of the measured structure. There are two methods to test the heat transfer coefficient of envelope on site: heat flow meter method and hot box method. The direct method must be tested in the stable period of heating in winter, even for heating buildings in the north, it has certain limitations, and it is even more inconvenient to apply it in hot summer and cold winter areas. Although the indirect method is basically not limited by the heating season in theory, in order to obtain the stable heat flux density on both sides of the tested structure, it is usually suitable to test in winter and summer.

1. Detection of rubber powder polystyrene particle thermal insulation slurry and vitrified bead thermal insulation slurry

Rubber powder polystyrene particle thermal insulation slurry consists of rubber powder and polystyrene particles. Vitrified microsphere thermal insulation slurry is a one-component dry-mixed mortar with vitrified microsphere as aggregate and uniformly mixed with modified dry powder binder. During construction, add water and stir evenly, and then smear or spray it on the grassroots wall. Its thermal insulation and mechanical properties are closely related to dry density. Dry density specimen size: rubber powder polystyrene particle thermal insulation slurry is 300mm×300mm×30mm, vitrified bead thermal insulation slurry is 70.7m×70.7mm×70.7mm, and compressive strength specimen size is100 mm×100 mm×100 mm, and the standard of thermal insulation slurry is prepared. After molding, cover the sample with polyethylene film. And maintenance.

2, adhesive, plaster slurry detection

In the national construction engineering industry standard, the test method of tensile bond strength of adhesive and plastering slurry in water in the external thermal insulation system of expanded polystyrene board thin plastering external wall. The conventional method is: put the coated adhesive and plastering mortar layer horizontally on the standard mortar, then inject water into the water surface about 5mm away from the surface of the mortar block, let it stand for 7 days, then take out the specimen and put it on the side for 24 hours, dry it in a constant temperature drying oven at 50℃ 3℃, and then put it under test conditions for 24 hours.

3. Detection of alkali-resistant mesh cloth

According to the national building industry standard and the test method of reinforced material woven fabric, the specimens of thin plastered expanded polystyrene board external insulation system were prepared, and the initial breaking strength F0 and elongation at break were measured. The conventional method is as follows: all the samples used in the alkali resistance test are immersed in 5%NaOH aqueous solution at 23℃ 2℃, and the samples are immersed in a closed container for 28 days; Take out the sample, soak it in tap water for 5 minutes, then soak it in flowing tap water for 5 minutes, then dry it in a constant temperature oven at 60℃ 5℃ for 65,438 0 hours, and then store it in a test environment for 24 hours to test the alkaline fracture strength of the sample.

4, thermal conductivity detection

Thermal conductivity is the main technical basis for evaluating the thermal insulation performance of thermal insulation materials. Its physical significance is that under the condition of stable heat transfer, when the temperature difference between the two sides is 65438 0℃, the heat passes through the unit area in unit time. The methods of measuring thermal conductivity of materials are mainly divided into steady-state method and unsteady-state method. According to the national standard for measuring the steady-state thermal resistance and related characteristics of thermal insulation materials, we use a flat thermal conductivity tester based on steady-state method to measure the thermal conductivity of materials. Thermal conductivity shall be determined according to GB/T 10294 or GB /T 10295, and arbitration shall be conducted according to GB/T 10294. The conventional thickness and temperature difference of the specimen are (25 1) mm for EPS board and (25 1) for XPS board. Temperature difference: EPS board l5℃-20℃, XPS board 15℃-25℃, average temperature: EPS board 25℃ 2℃, XPS board10℃ 2℃, 25℃ 2℃.

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