——Application of Thermal Insulation Lining Technology in Membrane Structure Building

Gangcha County is a county under the jurisdiction of Haibei Tibetan Autonomous Prefecture in Qinghai Province, and the performance center of the coastal Tibetan City on the Tsuowenbo Plateau in Qinghai Province is a landmark building in Gangcha County. The performance center is a circular building with a diameter of 50 meters. It uses double-layer membrane structure as the roof of the performance center. It belongs to the comprehensive roof structure system which used the insulation lining technology of membrane structure earlier in China.

The successful development and application of thermal insulation lining technology in membrane structure building breaks away from the dependence of building on traditional materials such as steel, wood and concrete, breaks the old architectural concept and creates new imagination space for architects. It is totally different from traditional architecture and has great influence on the basic disciplines of the future construction industry. It is the mainstream and trend of the development of architectural spatial structure in the 21st century.Because the thermal insulation lining material has the properties of heat preservation and light transmission, it has the advantages of energy saving, ecology and environmental protection. It greatly reduces the secondary pollution by getting rid of the traditional material. Moreover, because the new technology is only in place by tension, the construction speed is very fast, and the construction site is also very environmentally friendly. It guarantees the landscape effect of the building and the naturalness of the membrane structure, which reflects the regional architectural culture.

Exterior facade with Tibetan style
Architectural shape is the adjacent interface between urban public space and architectural space, and becomes a part of urban space. It is the first part of people's vision. Therefore, besides its functions, it should also have a strong identity and reflect the personality of the building. It is an important part of the architectural environment and urban landscape. Because the natural curvilinear beauty of membrane structure is incomparable with other structural types, it has become a commonly used form of building entrance and roof recently. The outer film surface of Gangcha Performing Arts Center is PVDF coated film with high frequency welding, which reflects the golden yellow film with obvious Tibetan decorative style and has strong ethnic characteristics.

The performance center roof thermal insulation lining material is a combination of PVDF coating, thermal insulation material and moisture-proof film. It is a new energy-saving, environmental protection and ecological material which can not only heat preservation but also transmits light for building roof system.

The lining can be designed according to the heat transfer coefficient design standards in different areas (see Table 1) and the sanitary standards of different functional buildings with different thicknesses. For example, the temperature of swimming pool, gymnasium and house is different. If the surface temperature of the swimming pool is low, condensation and human adaptation will occur.

Main technical characteristics:

1. Tolerance: The coating film of thermal insulation lining determines the tensile strength, tear strength, durability and flame retardancy of the film. Because the lining in the indoor wind, rain, snow, ultraviolet radiation has little impact on him, and basically does not withstand pre-tension (except for special requirements). So the material performance requirements for the outer membrane are much lower.

2. Thermal resistance coefficient: See the table of thermal resistance coefficient (see Table 3). It is emphasized here that the thermal resistance coefficient varies naturally with different bulk density and thermal conductivity. (coefficient of thermal resistance = thickness / coefficient of thermal conductivity)

Thermal resistance coefficient=thickness/thermal conductivity

3. Light energy: The surface of the outer film material can refract more than 70% of the light, so it has good thermal insulation performance, and the transmittance of the outer film can reach 20-25%. The inner lining is almost transparent. The transmittance of the insulation layer is 40-50%. The transmittance of the three layers is affected by some factors, but the transmittance can reach 10%. It can fully meet the needs of indoor lighting and plant growth.
4. Fire protection: The fire protection grade of the inner membrane can reach ASTMZ-136 standard. It has been registered by California Fire Protection Department and Los Angeles City Fire Protection Department and has reached multi-national standard. It has been widely used in Britain, France, Italy, Japan, Australia and Germany. The lining sandwich has good flame retardancy and can meet the domestic A1 level fire protection standard. Endometrium and adventitia can also meet Class A standard if they are made of tetrafluoroethylene.
Acoustics: Generally speaking, the sound absorption ability of a material is determined by its noise reduction coefficient. Membrane quality is almost transparent for reducing frequency noise, so the echo of noise in this frequency range can be well blocked and the sound absorption effect is very good. Especially in the waiting hall, waiting room, exhibition hall, the role of advantages are more reflected. The effect of the awning on toll island is more obvious. The same car echoes almost twice as well at toll stations in coloured steel and membrane buildings.
6. Architectural form: Architects can give full play to their imagination and give architects more space to imagine. Architecture is a reflection of regional culture. Membrane structure has a strong integration with the surrounding environment. Its structure is simple and visual sense is good. The change of external curvature is incomparable to any building, which fully reflects the beauty of nature and technology.
7. Good ecological effect: Because the light transmittance of the lining can reach 10%, it can completely meet the needs of indoor light. At the same time, the strong light is removed from the light transmitted by the membrane material, and the ultraviolet rays are filtered to diffuse light. It is very soft and makes people feel comfortable. The light is conducive to the growth of indoor trees and plants, thus meeting the needs of people to be close to nature and to nature. It's like feeling indoors or outdoors. (bilayer film, ecological film)

Case Study of Double-layer Thermal Insulation Membrane in Lhasa Sewage Treatment Plant
8. Energy saving:
(1) Thermal insulation performance: The film material has good thermal insulation performance. It can reflect 70% of the solar heat energy, absorb 17% of the film itself, and heat transfer 13%. Thus, the energy saving effect of venues in hot summer area is quite obvious. Consider the large-span space refrigeration is also a big problem, energy maintenance costs are high. The insulation performance of the membrane solves this problem well.
(2) Thermal insulation performance: Energy consumption of large-span space is a big problem, because the thermal insulation lining of membrane structure has good thermal insulation work (thermal resistance coefficient), so it can save energy consumption. (Reference to Thermal Resistance Coefficient Table) At the same time, its transmittance and outer film should be up to 10%. Without lighting during the day, it can meet the needs of indoor lighting, thus saving a lot of power consumption. Because of its energy-saving function, it is widely used in shared space buildings abroad and at present in China, as well as public buildings such as stadiums, exhibition halls, waiting halls, waiting rooms and so on.
9. Because the roof of membrane structure is lighter, the material consumption of main maintenance system and foundation system is reduced correspondingly, and the corresponding functional cost is reduced. At the same time, there is no need for secondary maintenance and decoration, which saves the decoration cost. A kind of
10. Fast construction:
When the membrane structure enters the site, it is only in place, and the construction speed is very fast. (Generally 1/2 of the time limit for steel structures)
11. Environmental protection: The use of membrane reduces the amount of steel used in space, reduces secondary pollution, and reduces the amount of sand, stone, steel structure welding, etc. at the construction site, which is very environmentally friendly.
Application area
An important function of membrane roof is to resist the influence of various weather changes (such as sunshine, rain, snow, etc.) on its interior space, and to maintain the comfort of the interior of the building. When choosing the shape and material of the membrane, all possible weather conditions should be taken into account, and passive methods such as the building itself should be used to reduce energy consumption as far as possible.
Now another project using double-layer membrane insulation has been started. It is also in the plateau climate changeable area. The insulation lining technology of membrane structure building will play a broader application space in various roof systems.

Scheme of Double-layer Thermal Insulation Membrane in Lhasa Sewage Treatment Plant

Other cases of double insulation inner film