External wall insulation materials are one of the main measures for building energy conservation. The waterproof function of building insulation layer has a significant impact on the energy-saving effect of building insulation, and even affects the functionality and durability of the building. This article mainly analyzes some important factors that affect the waterproof performance of building external insulation layers, and proposes corresponding technical measures. Others believe that external wall insulation materials are the cause of structural cracking in buildings.

 1. The structure of the insulation layer is not aligned, resulting in instability and cracking of the building structure.

In recent years, there have been many methods for building insulation in China. In order to reduce costs, some building units choose internal insulation, sandwich insulation, and self heating. These practices lead to the formation of two different temperature environments in the building envelope, resulting in different deformations in different temperature environments, causing unstable states of the external wall insulation materials of the building structure, and leading to cracks in the building structure.

Taking indoor insulation as an example, due to the influence of indoor temperature environment, the annual temperature difference between the inner wall of the insulation layer and the floor does not change much, generally within 10 ° C. The outer wall of the external wall insulation material is affected by the indoor environmental temperature. The annual temperature difference varies greatly, generally between 3060 ℃. When the temperature changes by 10 degrees, the deformation of thick walled materials is about one millionth. Due to the annual temperature difference deformation, the deformation difference between the inner and outer walls of a 50 meter high insulated building is 15-30 millimeters. Due to changes in the temperature environment on both sides of the insulation layer, a new temperature field is formed in the building. Compared to buildings without insulation, the motion state of buildings with insulation is very different. Different deformations can cause many cracks in the walls of different parts of the building structure, leading to water seepage from the exterior walls.

2. Incomplete external insulation leads to cracks in different parts of the building structure due to different deformations.

The structure of the external wall insulation material is reasonable. Avoiding the influence of outdoor environmental temperature on the deformation of building structures, the building structure is relatively stable. However, structural components such as balconies, canopies, drainage ditches, parapets, and roof decorations are not insulated, and the deformation caused by temperature is different from the external insulation of exterior walls. The crack at the intersection of the non insulated part and the external insulation part of the outer wall causes damage to the adjacent waterproof layer.

3. The difference in deformation speed between adjacent materials leads to structural cracking.

The thermal conductivity of concrete is 1.74W/(m · k), and the thermal conductivity of aerated concrete is about 0.2W/(m · k). The temperature difference between the two is about 8 times. The thermal conductivity of cement mortar is 0.93W/(m · k), and the temperature difference between cement mortar and aerated concrete is about 4-5 times. Due to the variation of temperature difference, cracks and gaps appear at the interface between the two materials at different deformation speeds. Especially the cracks between concrete frames and lightweight infill walls, aerated concrete blocks, and cement mortar surface will seriously affect the waterproof performance of the wall after one or two years of deformation and damage. Cracks will develop year by year, greatly reducing the waterproof performance of the wall.