(Design of the Sixth Design Institute of Machinery Industry, Zhengzhou 450007, China) can effectively ensure the quality and durability of the building. This article will combine the author's practical experience and analyze the design of building insulation, and make full use of favorable factors and disadvantages to be considered. Factors, at the same time put forward the measures for comprehensive treatment of building insulation design; combined with the actual situation of the project, in order to meet the building insulation requirements, the selection of insulation design scheme for building envelope system is proposed, which aims to provide reference for building insulation design.
0 Preface Insulation is one of the important functions of building envelope system and one of the important contents of building structure design. Insulation design should be carried out for all types of buildings in cold areas as well as buildings with non-cold areas but with air conditioning requirements. Through the thermal insulation design of the building, it can effectively ensure the insulation quality of the building and the reasonable use of construction investment; at the same time, it can effectively ensure the quality and durability of the building, and it is very important for reducing the investment in heating, energy conservation and air-conditioning equipment. The role.
At present, the building is insulated and designed, and the main part of the insulation is the external wall and the roof. In combination with the author's practical experience, in the use of the building, there are parts with large temperature difference and heat preservation requirements on both sides, and the insulation design should be adopted. Its building insulation design includes comprehensive insulation treatment in the design of the building scheme and insulation of the enclosure. This article will combine the practical engineering experience to further explore the two aspects of building insulation design.
1Integrated treatment principle of building insulation design In order to effectively achieve the better insulation effect of buildings, the principles of building insulation design should be fully grasped so that the buildings can satisfy these principles as much as possible, thus achieving the effect of keeping warm with half the effort. The author combines the practice and summarizes the design principles that should be mastered for the thermal insulation design of the building as follows: The building should have a good orientation and ensure that the building has proper spacing. When the building has a good orientation, solar energy can be effectively utilized to achieve energy saving and sterilization effects. The orientation of the building should not allow the large outer surface of the building to face the winter dominant direction to reduce convective heat transfer losses.
Select the effective building shape and plane form, and grasp it by the figure coefficient (S) of the building. The body shape factor (S) is the ratio of the outer surface area of ​​a building in contact with the outdoor atmosphere to the volume it encloses. The shape factor of a building has different requirements for different regions and different building layers, as shown in Table 1.
Table 1 Building shape coefficient stipulates that the number of building layers is 3 layers, 10 layers, cold regions, cold regions, hot summer and cold winter regions, mild regions, A hot summer and warm winter regions, and mild regions, B, should not limit the insulation of building envelopes. Performance, so that the building's envelope structure has good thermal performance. Therefore, at the time of design, the total thermal resistance of the building envelope structure is not lower than the minimum thermal resistance, so as to effectively control the inner surface temperature; at the same time, it should have a certain thermal stability, avoid moisture, and prevent condensation in the wall.
In addition to the insulation properties of the envelope structure, the window walls of the building will have a greater impact on the heat consumption of the building. Therefore, appropriately reducing the window-to-wall ratio of the building and strengthening the tightness of the building can effectively avoid the adverse effects of cold air infiltration. For avoiding cold air infiltration, an effective way can be adopted by increasing the tightness of the building, for example, reducing the door and window openings of the building and reducing the weak links, such as setting the door bucket and avoiding the dominant wind direction.
2 The comprehensive design technology of building insulation design integrates the above-mentioned comprehensive principles of building insulation design. When constructing building insulation design, it should make full use of favorable factors. For example, when the building has a good orientation, solar insulation measures should be effectively utilized.
For the south-facing large window, a large amount of sunlight is penetrated during the winter season, and a special insulating curtain or insulation board is used to block the window at night. The indoor floor needs to be made of materials with high heat storage capacity, such as brick or concrete. It absorbs heat during the day and stores heat. It is released to the room at night to maintain a certain temperature in the room. The other facing structures are strengthened as much as possible. Keep warm and reduce heat loss.
For the case where there is sunlight adjacent to the main room, there is not only a large window in the sunlight, but also the regenerator on the ground. The sunlight is stored on the regenerator through the glass to store heat, thereby increasing the indoor temperature, while the main room is through the sunlight. Heat is obtained between adjacent walls or windows. Use a thermal curtain at night to separate the sunlight from the main body. In addition, in order to effectively prevent overheating in the summer, there should be adjustable venting and shading measures above the window.
Measures to reduce the impact of cold winds. As far as possible, the large outer surface of the building should not be oriented towards the winter dominated wind direction. When the conditions are limited and the dominant wind direction cannot be avoided, the doors and windows should be opened as little as possible on the windward side. At the same time, make full use of the surrounding natural conditions to block the wind.
The thermal characteristics of the room should be suitable for its use. For example, the room used throughout the day should have greater thermal stability. In case of outdoor temperature drop or intermittent heating, the room temperature fluctuates too much; for rooms that are only used during the day, After the start of heating, the room temperature can rise to the required standard faster. For indoor and outdoor temperature fluctuations, in order to maintain the required standard of indoor thermal environment, the intermittent time of heating in the heating mode should not be too long, in case the night temperature does not reach the basic thermal comfort standard.
3 Insulation design of building envelope structure The insulation of building envelope structure is mainly reflected in exterior wall insulation design and roof insulation design, while exterior wall insulation is a very important part of building insulation design. This paper will focus on the insulation design of external wall. Conduct an in-depth discussion.
3.1 Theoretical analysis of external wall insulation design At present, the design method adopted for the insulation design of the external wall of the building is mainly the minimum thermal resistance method, as shown in formula (1). However, when the actual insulation design of the building, such as residential buildings, hospitals, kindergartens, office buildings, schools and clinics, the outer wall of the building is light material or the inner composite lightweight material, the minimum transmission of the outer wall The thermal resistance shall be added on the basis of the calculation of the minimum thermal resistance obtained by the formula (1), and the additional value shall be adopted as specified.
Degree, n is the temperature difference correction coefficient, which can be obtained by looking up the table; Ri is the internal surface heat transfer resistance, m2.K/W; At is the allowable temperature difference between the indoor air and the inner surface of the outer wall. 3.2 External wall insulation design considerations As the main component of the building envelope structure, the wall's insulation capacity requirements depend on the nature of the use of the room and the technical and economic conditions. The author proposes that the following aspects should be considered: 1 The inner surface of the outer wall should be fully guaranteed. Dew, that is, the inner surface temperature of the external wall of the building should not be lower than the dew point temperature of the indoor air; 2 for civil buildings, not only to ensure that the inner surface of the outer wall does not condense, but also to meet certain thermal comfort conditions, restrictions The internal surface temperature, so as to avoid excessive cold radiation effects; 3 the exterior wall of the building should have a certain thermal stability.
3.3 Building exterior wall insulation design program In order to meet the building insulation requirements, the common exterior wall insulation design has the following options: adopt a single material insulation design. This design is made of a material with a small thermal conductivity as the insulation layer to meet the insulation requirements of the external wall. The thermal insulation material used in this design has a relatively high thermal insulation performance; since the thermal insulation material does not bear the weight bearing effect, the flexibility of the selection is relatively large.
For example, aerated concrete block wall or light hollow block wall, this insulation design is suitable for the insulation wall insulation requirements of non-load bearing structure.
Insulation design combining bearing material and thermal insulation material. This scheme is characterized by simple construction and convenient construction. In the aspect of thermal insulation materials, the thermal conductivity should be relatively small, and the material strength should meet the bearing requirements, and at the same time have sufficient durability. For example, a reinforced concrete wall or a masonry structure wall, a cement perlite mortar insulation layer on the inside, and a 2 mm thick paper ash cover. This thermal insulation design can be used for wall insulation of the external wall bearing structure.
Insulation design for mixed practices. In the case of a separate construction method that still fails to meet the insulation requirements, or in order to meet the construction insulation requirements, the technically unreasonable design can be adopted. For example, there are both an insulating layer of solid material and an outer wall enclosing the air interlayer and the load-bearing structure. The thermal insulation design of this thermal insulation design is more complicated, but has better thermal insulation performance, especially for the exterior wall of buildings where high thermal requirements are required. For example, for a reinforced concrete wall, a closed air interlayer of 40 mm or more is placed in the middle of the wall, and a 4 mm thick plastic coated double-layer aluminum foil board is laid at the same time. This hybrid exterior insulation design can be adapted to buildings with higher insulation requirements.
3.4 Insulation design of the abnormal part of heat transfer of the external wall of the building The above proposed external wall insulation design is for the main part of the external retaining wall body, for the part of the external wall where the heat transfer is abnormal, such as the outer wall In the middle of the beam and so on. The heat loss of these heat transfer abnormal parts is more than the heat loss of the same area of ​​other parts. For these "cold bridge" parts with weak thermal performance, corresponding insulation design measures must be taken to effectively ensure the normal indoor room of the building. climate.
The insulation design of the joints between the prefabricated exterior wall panels. Considering the insulation requirements of the peripheral siding, a high thermal resistance material with a thickness of 50-100 mm is added to the pre-fabricated exterior wall panel in the middle of the thickness of the panel, which can effectively solve the problem of insulation of the main part of the façade panel. However, at the connection node of two adjacent prefabricated exterior wall panels, due to the need of on-site processing of structural connections, it is impossible to form a composite wall panel with insulation function, and it is easy to form a "cold bridge" for such joints. "Special insulation construction must be carried out on site.
Insulation design of common heat transfer abnormalities in walls. Reinforced concrete beams, lintels and other components in the building are more likely to form "cold bridges". In order to avoid excessive heat loss in these "cold bridge" parts and possible condensation on the inner surface, local parts should be taken at these parts. Insulation construction measures.
4 Conclusions This article will combine the author's practical experience, analyze the construction insulation design, make full use of the favorable factors and the unfavorable factors to be considered, and at the same time put forward the measures for the comprehensive treatment of building insulation design; combined with the actual situation of the project, in order to meet the building insulation requirements, The selection of insulation design schemes for building envelope systems is intended to provide a reference for building insulation design. ID: 6836
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