External wall insulation, external wall internal insulation, sandwich insulation

(1) The first is the external thermal insulation of the external wall. This technology is to install the thermal insulation layer on the outer surface of the external wall, which is composed of thermal insulation layer, protective layer and fixing materials.

The advantages are: high thermal performance, good heat preservation effect, and low comprehensive investment. It is not only suitable for new construction, but also for old building renovation, with a wide range of applications. The insulation layer is wrapped on the outside of the main structure to protect the main structure and prolong the life of the building. Basically eliminate the influence of hot (cold) bridges, at the same time eliminate condensation and mildew, and improve the comfort of living.

The disadvantages are: because the insulation layer is on the outside of the wall and the environment is harsh, the requirements for the materials of the insulation system are strict; the material requirements are matched and compatible with each other; higher requirements are placed on the weather resistance and durability of the insulation system; construction The difficulty is large, and there must be a better-quality construction team and technical support.

(2) The second is the internal insulation of the external wall. This technology is to add an insulation layer inside the external wall structure.

The advantage is: because the insulation layer is on the inside, the temperature of the inner surface of the wall drops rapidly with the drop of air temperature in the evening in summer, reducing the sultry feeling. The durability is better than the external insulation of the external wall, which greatly increases the service life. Conducive to safety and fire prevention. The construction is convenient, and it is less affected by wind and rain. The construction is simple, the cost is relatively low, and the construction technology and inspection standards are relatively complete.

The disadvantage is that it is difficult to avoid hot (cold) bridges, which reduces the thermal insulation performance, and it is prone to condensation, humidity and even mildew on the inner surface of the outer wall of the hot bridge. The insulation layer is built indoors, which not only occupies indoor space, but also reduces the usable area. Moreover, the user's secondary decoration or additional hanging facilities will cause damage to the insulation layer, which is not easy to repair. It is not conducive to the protection of the building envelope. Cracks in the thermal insulation layer and walls have become a common phenomenon, while the internal thermal insulation cracks are always in the eyes of the residents, which will have a long-term impact on the residents' aesthetics and psychology, and become the focal point of complaints.

(3) The last is sandwich insulation. This technology puts the insulation material between the inner and outer walls of the same outer wall. Both the inner and outer walls can be made of traditional clay bricks, concrete hollow blocks, etc.

The advantages are: good waterproof, weather resistance and other properties, which form an effective protection for the inner wall and insulation materials. The selection of insulation materials is not demanding, and various materials such as polystyrene, glass wool and rock wool can be used. The requirements for construction season and construction conditions are not high, which will not affect winter construction.

The disadvantage is: due to the influence of the thermal bridge, the insulation performance of the wall is weakened. The beams and columns that combine the steel bars and the wall are still thermal bridges; the outer wall sandwich insulation wall is thicker, reducing the effective use area. The seismic performance is poor. Because the insulation layer is between the two load-bearing rigid walls; the joints of the prefabricated panels are prone to leakage; the outer wall sandwich insulation is likely to cause damage to the wall structure due to large temperature fluctuations at both ends of the structure.

Thermal conductivity and heat storage coefficient of external wall insulation

Thermal conductivity: Thermal conductivity refers to the heat transfer through an area of 1 square meter in 1 second (1S) for a material with a thickness of 1m and a temperature difference of 1 degree (K, ℃) on both sides under stable heat transfer conditions [Unit: W/(MK)]. The thermal conductivity of a material is numerically equal to the thermal density divided by the negative temperature gradient. It is generally believed that the smaller the thermal conductivity of the thermal insulation material, the better the thermal insulation effect of the material.

Material heat storage coefficient is divided into material heat storage coefficient and surface heat storage coefficient.

The heat storage coefficient of a material is generally the ability of the material to store heat.

The surface heat storage coefficient refers to the heat stored or released in a surface area of 1 square meter within 1 hour when the surface temperature of an object increases or decreases by 1 ℃ under the action of periodic heat. The larger the value, the better the thermal stability of the material.

As the saying goes, the smaller the heat storage coefficient, the faster the heat will come, and the faster it will go when it is cold.