Problems with external wall insulation
After the assessment, we can know that the external wall insulation systems used in my country's construction market mainly include the following types: polystyrene board thin plaster insulation system, rubber powder polystyrene particle insulation system, steel wire grid insulation system, polyurethane insulation system5, Extruded polystyrene board insulation system. Although these kinds of external wall insulation systems have their own advantages and characteristics, they all have disadvantages of different degrees, mainly as follows.
1. Thin plastering of polystyrene board.
①Limited by the strength of the EPS board, it will be damaged and cracked when it is not plastered.
② There is a cavity and it is easy to fall off.
③ It does not match the life of the building.
④ Heavy finishes are limited.
2. Rubber powder polystyrene particles.
① The thickness of the insulation layer is uneven, which affects the insulation effect.
②The rubber powder has poor water resistance and weather resistance. When the rubber powder cement mortar is bonded to the polystyrene board, the initial bonding force is relatively large. With the passage of time, the adhesive strength of the rubber powder gradually dissipates and is not durable.
③ Two-component on-site batching construction, the operability is not good, and the thermal insulation coefficient is difficult to guarantee.
3. Steel wire mesh frame.
①It does not have good operability.
② The proportion of data components is not determined.
③ Durability is doubtful.
4. Polyurethane.
① The formula and ratio of thermal insulation boards are chaotic and unstable, resulting in poor physical stability of the boards and poor thermal insulation effects.
② The construction of spraying has not been solved, and it is difficult to guarantee the quality of the project.
5. Extruded polystyrene board.
①The XPS board is not firmly bonded to the plastering mortar, and it is easy to fall off.
②External tiles fall off faster and more seriously.
③The permeability is poor, and condensation is inevitable.
Based on the above analysis, it is not difficult to find that the most prominent and critical problems of the several types of external wall insulation systems commonly used in the construction market in my country are easy to crack, easy to fall off, poor durability, insufficient thermal insulation performance, poor permeability, and poor construction operation. The method is not determined, the control method is not in place, etc. Especially for the widely used polystyrene board thin plaster and extruded polystyrene board insulation system, the hidden danger of falling off has become an unexpected real disaster. Mr. Chen Fuguang, deputy director of the Science and Education Committee of the China Building Materials Industry Association, has already reminded everyone that he clearly and firmly pointed out: "Practices at home and abroad have proved that if the quality of this external thermal insulation method cannot be guaranteed, it is very prone to the disadvantages of mortar cracking and grid cloth falling off. The lifespan is the same as that of buildings, especially buildings with high-rise frame and frame-shear structures, once this phenomenon occurs, it is difficult to remedy and repair, and there will be endless troubles."
Reasons and Countermeasures
The reasons for thermal insulation cracking and shedding of external wall insulation materials are quite complex. The following mainly analyzes the reasons for cracking and shedding in the construction process. Since the external thermal insulation grid cloth of the external wall is usually completed at the construction site, the quality of the construction is very important to ensure the quality of the external thermal insulation system.
1. There are hidden dangers of cracks during the treatment of the base and the pasting and fixing of the insulation layer on the base. The main reasons are: the flatness of the surface of the base does not meet the quality requirements of the allowable deviation items of the external insulation project for the base, and the deviation of the flatness is too large. The surface of the base layer contains substances that hinder pasting, and no interface treatment has been performed on it. The adhesive used does not meet the quality and performance requirements of the external thermal insulation technology, or the embedding depth and number of anchors do not meet the requirements of the design specifications when mechanical fixation is adopted.
2. Cracks on the wall surface caused by the external thermal insulation construction of the paint finish. Due to construction factors, the reasons for the cracking of the external thermal insulation wall surface of the paint finish are: the grid cloth is drily lapped or the lap is not enough, and cracks are formed at the lap joint; the position of the mesh cloth is close to the thermal insulation layer, which cannot Anti-cracking effect, the plastering mortar layer is prone to cracks. Construction in winter is prone to cracking, hollowing, and falling off. Grinding is used for leveling. This method damages the dense structure of the polystyrene board surface, affects the bonding with the plastering mortar, and also reduces the thermal insulation effect of the thermal insulation layer when the grinding thickness is too large. When constructing the surface layer, if the layer is exposed to the sun or under high-temperature weather, the water retention performance of the layer is insufficient, which will cause the surface layer to lose water too quickly and cause cracking.
