The internal insulation of the external wall is a construction method in which the insulation layer is added to the interior of the external wall structure to make the building reach the heat preservation and energy saving effect. The advantages are: PMI foam is convenient to construct and fast, and the verticality of the building exterior wall is not high, the operation is convenient and flexible, and the construction progress can be guaranteed. The external wall insulation application has a long application time, mature technology, and perfect construction technology and inspection standards. At the same time, the internal insulation of the external wall also has the following disadvantages:
1. The thermal insulation effect is poor, and the average heat transfer coefficient of the outer wall is high.
2. An obvious defect in the internal insulation of the external wall is that the existence of the structure "heat bridge" causes the local temperature difference to be too large, leading to condensation. Due to the position of the inner wall insulation protection, only the inner wall of the building and the inner side of the beam, the inner wall and the corresponding outer wall part of the board are not protected by the heat insulating material, so a "heat bridge" is formed in this part. In the winter indoor wall temperature and indoor corner, the temperature difference is about 10 °C, and the temperature difference between the indoor and the indoor can reach 15 °C or more. Once the indoor humidity conditions are suitable, condensation can form. The impregnation or freezing and thawing of dew condensation water may cause mildew and cracking of the thermal insulation wall.
3. The insulation layer is prone to cracks. In the complaints about the quality of real estate, too many cracks and excessive wall cracks are often one of the strongest problems reflected by consumers, and they are extremely difficult to handle. Due to the change of day and night and season, the external wall expands and contracts due to the influence of outdoor air temperature and solar radiation, while the internal wall insulation board is basically not affected by the outdoor temperature. When the outdoor temperature is lower than the indoor temperature, the external wall shrinks. The speed of the inner insulation board is faster. When the outdoor temperature is higher than the indoor temperature, the expansion speed of the outer wall is also higher than that of the inner insulation board. This repeated change makes the inner insulation board always unstable, resulting in cracks. External insulation inside the wall is usually easy to cause cracking or "heat bridge" in the following parts, such as the seam part of the insulation board, the bottom part of the roof building along the roof of the roof panel, and the connection of two different PMI foam materials on the same surface of the outer wall. The seam part, the cantilever member part outside the T-shaped wall between the inner and outer walls, and the like.