In June 2004, Beijing took the lead in issuing the design standard of 65% building energy efficiency. According to the national energy saving development plan, the standard of 75% energy saving will be fully implemented by 2020, and Beijing may start to implement it in 2008. Zhen group, an early domestic construction enterprise engaged in building energy conservation, took the lead in the experimental transformation of low-energy buildings of the company's office buildings around the concept of "making green environmental protection community and creating low-energy boutique residence". For the energy-saving transformation of external wall insulation, after many verification, it is finally decided to adopt the composite insulation system of Extrusion board and vitrified micro bead insulation mortar. The system belongs to internal and external mixed insulation, with external insulation as the main part, and the inner side is plastered with 30mm thick vitrified micro bead insulation mortar. The principle of this scheme is: temperature gradient, layer by layer excessive, scattered stress, layer by layer release.

As we all know, temperature cracks are caused by the joint action of temperature and drying shrinkage, which accounts for a considerable proportion of the cracks in the external wall. To solve the cracks in the external wall, we must first solve the temperature cracks. The linear shrinkage of the glazed bead insulation mortar is very small, and the anti crack mortar on its surface is composed of high molecular polymer modified material and high modulus and high elastic alkali resistant fiber, which has good anti crack effect. The thermal insulation mortar placed in the outer layer can effectively protect the inner organic thermal insulation material from the external adverse conditions, and at the same time, it can not make the surface of the organic material reach the critical temperature and produce degradation and thermal shrinkage. When the thickness of extruded board reaches 70mm and polystyrene board reaches 90mm, the insulation effect is almost high. It is not economical to continue to increase the thickness. It is an excellent way to supplement it with glazed bead insulation mortar. In addition, the thermal insulation mortar insulates part of the heat and allows part of the heat to pass through. It is treated by the organic thermal insulation material on the inside, so that the temperature difference between the two layers is not too large, and the probability of cracks is reduced, so that both materials can give full play to their role, so as to achieve the effect of thermal insulation and create a high comfortable living environment.

The original external wall structure of this office building is 360 fair faced brick wall. After watering, cleaning and moistening, the external wall is leveled with 3-5mm mud mortar. After 15 days of curing, 70 mm thick extruded board is pasted. The construction method of gluing and anchoring is adopted for the gluing of the extruded board. A 50 mm wide and 15 mm high adhesive tape is plastered around the board, and 8-10 mm bonding points are plastered in the middle. The bonding surface is not less than 40%. 24 hours after the construction of pasting extruded board is completed, holes shall be drilled on the wall to install anchors. The effective anchorage length into the structural wall shall be 40mm, with at least five anchors per square meter, and the anchor surface shall be provided with a pressure plate with a diameter of not less than 50mm. After that, the alkali resistant plastic coated glass fiber gridding cloth is fully paved and the anti crack mortar is scraped. Among them, the {hottag} expanded glass bead thermal insulation mortar developed by Beijing huaweijia Technology Co., Ltd. is selected. In the construction process, through on-site random sampling, it is sent to the national building materials industry testing center for freeze-thaw resistance test, and it is sent to the test after natural maintenance for 10 days. After 25 freeze-thaw cycles from – 25 ℃ to + 65 ℃, there are no cracks, hollows, blisters and peeling on the surface, and the compressive strength loss is only 7%. The test results meet the requirements. Seven days after the construction and maintenance of the anti crack mortar for the extruded board, the thermal insulation mortar plastering construction is carried out. Firstly, the 25 mm thick thermal insulation mortar is plastered, and the surface is smoothed with a trowel. After hardening, the high-quality hot-dip galvanized steel wire mesh is fully paved, and then the nylon expansion bolt is installed. The two-way middle distance is 500 mm, not less than four per square meter, and it extends into the structural wall for 40 mm to connect with the steel wire mesh. Then, apply 15mm thick insulation mortar, smooth the surface with trowel, maintain naturally for 3 days, and scrape 2mm anti crack mortar in time. So far, the whole construction of thermal insulation mortar is completed. After the wall is dry, apply elastic water-resistant putty and brush exterior wall paint.

In addition to good thermal performance, this kind of insulation system also has good fire performance: the fire resistance of vitrified beads is 1280 ~ 1360 ℃, which improves the fire rating of buildings; Reliable durability: because the glass beads are inorganic materials, their stability and weatherability are higher than those of organic materials; It is convenient for the selection and construction of exterior wall coating: the solvent of oily coating enters the plastering layer through capillary holes, when it reaches the surface of organic thermal insulation material, it will degrade the thermal insulation material, thus destroying the whole thermal insulation system; It has good cost performance, safety and good energy saving effect.

At present, this kind of insulation system has passed the expert review, and the standard atlas and construction technical specification have been prepared. According to experts, the system is especially suitable for energy saving and thermal insulation requirements in cold and severe cold areas, and has great application value.