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At about 14:00 on August 22, the external wall of the Xintiandi Building in Nankai District, Tianjin, caught fire. The fire was visible from the roof of the podium of the east facade of the building to the top floor of the building. Subsequently, Tianjin emergency, fire and other departments quickly rushed to the scene, fully engaged in fire fighting and personnel evacuation work. According to China's fire official microblogging news, Tianjin Fire and Rescue Headquarters organized a number of search and rescue groups into the fire Xintiandi building to carry out personnel search and rescue, so far no casualties have been reported.
Obviously, the building's exterior wall was ignited, resulting in the spread of fire, fire in the briefing also clearly pointed out that "the building's external thermal insulation layer open fire", building insulation materials again caused concern. In recent years, the insulation material caused by the high-rise building fire, or because of the fire caused by the insulation material on fire case is increasing. Why the exterior wall insulation repeatedly "trouble", triggering people's attention.
High-rise building outer insulation material fire difficult to extinguish
Fire caused by insulation materials or fire caused by fire insulation materials on fire in an increasing number of cases, the combustion characteristics of the exterior insulation materials and construction process led to the material in the event of a fire extinguishing difficulty, especially high-rise buildings of the exterior wall insulation materials on fire is more difficult to extinguish the fire, the main difficulties are the following points:
It burns fiercely and spreads quickly：
The use of flammable and combustible materials as external heat preservation materials, if not treated with flame retardant, it is very easy to form a three-dimensional fire. For example, Shanghai Jing'an District, Jiaozhou Road Teachers' Apartments fire, after the fire, in the building facade quickly burning, while by the high wind and fire microclimate and other factors, through combustion, heat radiation and flying fire, making the fire spread rapidly, only about 6 minutes, smoke and fire will be the whole building covered.
Smoke generates high heat and produces toxic gases：
Insulation materials made of organic materials contain a large number of unsaturated groups, belonging to the chemical reactivity of very high compounds, combustion heat and smoke are very large.
It burns invisibly, imperceptibly：
Insulation materials are often filled in the interlayer, due to better closure, when ignited, in the case of low oxygen concentration, the initial stage is generally negative combustion, from the outside is difficult to find, and the amount of organic thermal insulation material smoke, rescue workers are difficult to find the fire point in the first time to carry out the attack, and so on the discovery of open flames, the fire spreads rapidly to miss the best time to rescue, it is difficult to control.
Why the exterior wall insulation materials repeatedly become "fire accomplices"
China since the mid-1980s began to apply the application of building exterior wall insulation materials, but only until 2009 formally introduced civil building exterior insulation materials fire performance aspects of the relevant provisions.
The Ministry of Emergency Management experts Hu Anxiong introduction, before 2009, around the world commonly used extremely flammable polyurethane foam as thermal insulation materials. Over time, some of the building's exterior wall insulation materials covered by the surface of the protective layer of plaster cracking, falling off, flammable, combustible insulation materials exposed. In the event of an ignition source, it is very easy to burn, and will rapidly expand and spread, forming a three-dimensional fire on the facade of the building.
As far as the current application of external wall insulation materials for buildings is concerned, according to "Classification of Combustion Performance of Building Materials and Products" (GB8624-2012), our country classifies building materials into four combustion performance levels - A, B1, B2, B3, corresponding to non-combustible, flame-retardant, combustible and flammable materials (products) in that order.
GB50016-2014 requirements for the use of thermal insulation materials
GB50016-2014 "Building Design Fire Prevention Code" (2018 Revision) clearly stipulates that the internal and external insulation system of the building, it is appropriate to use thermal insulation materials with combustion performance of grade A, it is not appropriate to use grade B2 thermal insulation materials, and it is strictly prohibited to use grade B3 thermal insulation materials.
The Fire Safety Management Provisions for High-Rise Civil Buildings issued by the Ministry of Emergency Management, which came into effect on August 1, 2021, explicitly prohibits the use of flammable and combustible materials as external thermal insulation materials for the exterior walls of high-rise civil buildings.
Since June 1, 2023, the implementation of the "General Specification for Fire Protection in Buildings" (GB55037-2022), the provisions of the building external thermal insulation materials are more detailed, except in specific cases of independently constructed facilities for the care of the elderly, densely populated places, etc., requires the use of combustion performance of Class A thermal insulation materials or products.
Many places issued documents to ban exterior wall insulation technology
Liaoning
On July 13, 2023, the Liaoning Provincial Department of Housing and Construction issued an announcement on soliciting opinions on the Catalogue of Promoting and Applying Technologies and Restricting and Prohibiting the Use of Technologies for External Wall Insulation Projects of Housing Buildings in Liaoning Province (the first batch) (draft).From May 1, 2024, the use of restricted external wall insulation technologies will be prohibited for the projects of new building construction, alteration, and expansion of high-rise civil buildings (residential buildings > 27m; public buildings > 24m (excluding single-story buildings)) ) projects using restricted types of external wall insulation technology. It is strictly prohibited to use products of prohibited types of technologies in external wall insulation systems.
Sichuan
On November 2, 2022, the Sichuan Provincial Department of Housing and Construction issued the "Sichuan Provincial Housing and Urban-Rural Construction Field Promotion and Application of New Technologies and Restriction and Prohibition of the Use of Outdated Technologies (the first batch)", heat preservation and insulation materials: prohibited: 1, the use of hexabromocyclododecane as a flame retardant production of thermal insulation materials. 2, B2, B3 level thermal insulation materials. 3, slurry-type thermal insulation material.
Jiangxi
On September 21, 2022, the Jiangxi Provincial Department of Housing and Construction issued the Notice on Soliciting Opinions on <Notice on Further Strengthening the Construction Quality Management of External Wall Thermal Insulation Projects in Housing Buildings>, which proposed that: it is prohibited to use the external thermal insulation system of thin plastered external walls and the external wall thermal insulation and decorative integration system fixed only by bonding anchors in high-rise buildings. Prohibit the use of combustion performance indicators lower than B1 level of insulation materials. Priority is given to the use of internal heat preservation, external self-insulation, composite heat preservation and assembly of new external wall insulation system, limiting the use of thermal insulation slurry and only through the bonding of fixed thermal insulation panels and other forms of external wall insulation system.
Tianjin
In September 2022, the Tianjin Municipal Commission of Housing and Construction made the second public announcement of the "Catalog of Promoting, Restricting and Prohibiting the Use of Building Energy Efficiency Technologies, Processes, Materials and Equipment in Tianjin (2021 Edition)". Prohibited use of 16 items, including: on-site cement-mixed mortar paste external wall finishing brick process, the use of HBCD as a flame retardant production of thermal insulation materials, the core material is non-incombustible metal sandwich composite panels and so on. Restrictions on the use of 29 items, including: slurry insulation materials, wall materials made of shale as raw material and masonry materials.
Hebei
Hebei Provincial Department of Housing and Construction issued "Hebei Province, civil construction of external wall insulation project unified technical measures", since July 1, 2021 onwards. Prohibited use: 1, construction site using cement or anchor bolts and the combination of the two ways of thin plaster exterior insulation system. 2, combustion performance of B2 class materials. 3, recycled material production of insulation with extruded polystyrene foam board.
Chongqing
On March 26, 2021, the Chongqing Municipal Housing and Urban-Rural Development Commission issued a notice on the Technical Requirements Relating to the Prohibition of Outer Wall Insulation Works for Civil Buildings. The notice requires: since January 1, 2022, through the construction plan review or due to the design table change and other reasons need to re-conduct the program design or preliminary design of the main urban metropolitan area within the scope of the new construction, alteration, expansion of civil building projects, prohibit the use of thin plaster exterior wall external insulation system and only through the bonding anchors to fix the integrated system of exterior wall thermal insulation and decoration. Since July 1, 2022, through the construction plan review or due to the design table change and other reasons need to re-conduct the program design or preliminary design of the city-wide new construction, alteration, expansion of civil construction projects, prohibit the use of thin plaster exterior wall external insulation system and only through the bonding anchorage method of fixing the exterior wall thermal insulation decorative integration system.
Further enhance the scale of application of wall self-insulation technologies such as self-insulation of non-load-bearing wall blocks, integration of structure and heat insulation, and prefabricated heat-insulating exterior wall panels.
Although the current standards have been raised, the risk of fire from external insulation in stock buildings still exists. For previously constructed old buildings, demolition and replacement has a certain degree of difficulty, you can carry out remodeling and expansion projects, can be replaced as far as possible. For the difficult to replace to strengthen the management, maximize the control of fire, power, to take the setting of conspicuous signs, demarcation of safety areas, the implementation of inspection and guarding and safety precautions.
Solve the fire in the construction process of external insulation should start from strengthening the construction site management, should be for the construction of the external insulation project to establish fire safety standards, from the perspective of thermal insulation materials stacking, construction fire prevention and finished product protection and other points of view of the corresponding management measures, strictly avoid the external insulation and fire welding cross operation. If the construction fire safety standard measures are appropriate, in place, the fire caused by the construction process will gradually reduce.
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