Thermal Insulation Fire Rating
In China, exterior thermal insulation materials are primarily categorized into four grades: A, B1, B2, and B3. Grade A is non-flammable, belonging to inorganic thermal insulation materials. B-grade insulation materials are further divided into three levels, with B1 being flame-resistant, B2 being combustible, and B3 being highly combustible.
B1 Grade: Commonly found are flame-retardant treated EPS/XPS insulation boards. B2 Grade: Combustible insulation materials, often in the form of EPS expanded polystyrene and XPS extruded boards, commonly known as standard boards. These materials have a low ignition point and release a large amount of harmful gases during combustion.
B3 Level: Combustible Insulation Materials, commonly made of polystyrene foam, these insulation materials are considered outdated exterior insulation due to their flammability.
Exterior Wall Insulation, Interior Wall Insulation, Sandwich Insulation
(1) First is the exterior wall thermal insulation technology, which involves installing the insulation layer on the outer surface of the wall, composed of the insulation layer, protective layer, and fastening materials.
Advantages include high thermal performance, excellent insulation, and low overall investment. Suitable for both new construction and renovation of existing buildings, it boasts a wide application range. The insulation layer wraps around the exterior of the main structure, protecting it and extending the building's lifespan. It effectively eliminates the impact of thermal (cold) bridges, while also preventing condensation and mold growth, enhancing the comfort of living spaces.
The drawbacks include: Due to the insulation being on the exterior of the wall, the environment is harsh, which requires strict standards for the materials in the insulation system; materials must be compatible and well-matched; higher demands are placed on the weather resistance and durability of the insulation system; construction is challenging, necessitating a skilled workforce and technical support.
(2) Next is the internal thermal insulation of the outer wall, a technique that involves adding an insulating layer to the interior of the outer wall structure.
Advantages include: Due to the insulating layer on the inside, the inner surface temperature of the walls rapidly drops with the decrease in air temperature during summer evenings, reducing stuffiness. The durability is superior to external wall insulation, significantly extending the service life. It is conducive to fire safety. Construction is convenient, with minimal impact from windy and rainy weather. The construction is simple, with relatively lower costs, and the construction technology and inspection standards are relatively完善.
Drawbacks include: The unavoidable thermal (cold) bridges can reduce the insulation performance, leading to condensation, dampness, and even mold on the interior surface of the outer wall at the thermal bridge areas. Insulating layers applied indoors not only occupy living space, reducing usable area, but also are prone to damage during subsequent renovations or installation of hanging equipment, making repairs difficult. This is not conducive to the protection of the building's outer envelope. Cracks in the insulation layer and walls are a common occurrence, and internal insulation cracks are constantly in the occupants' line of sight, which can have a long-term impact on their aesthetics and psychology, becoming a frequent point of complaint.
(3) Insulation Sandwich Technology - This technique involves placing insulation material between the inner and outer wall panels of the same exterior wall. Both the inner and outer wall panels can be made of traditional materials such as clay bricks or concrete hollow blocks.
Advantages include excellent waterproofing and weather-resistant properties, effectively protecting the interior wall panels and insulation materials. The material selection for insulation is not stringent, allowing the use of various materials such as polystyrene, glass wool, and rock wool. There are minimal requirements for the construction season and conditions, ensuring it does not hinder winter construction.
Drawbacks include: The thermal bridge effect weakens the insulating performance of the walls; the beams and columns joined with the walls are still thermal bridges; the thicker exterior sandwich insulation walls reduce the effective usable area; poor seismic performance; the insulation layer between the two load-bearing rigid walls is prone to leakage at the precast panel joints; and the exterior sandwich insulation is susceptible to structural damage due to significant temperature fluctuations at the ends of the structure.
Thermal Conductivity and Heat Storage Coefficient of External Wall Insulation
Thermal Conductivity: Thermal conductivity refers to the amount of heat transferred through a material of 1m thickness under steady-state heat transfer conditions, with a temperature difference of 1 degree (K, °C) across the two surfaces within 1 second (1S) through an area of 1 square meter. The thermal conductivity of a material numerically equals the heat density divided by the negative temperature gradient. It is generally believed that the lower the thermal conductivity of an insulating material, the better its thermal insulation effect.
Thermal mass coefficient is divided into material thermal mass coefficient and surface thermal mass coefficient.
Thermal storage coefficient, in layman's terms, refers to a material's ability to store heat.
The surface heat storage coefficient refers to the amount of heat stored or released by a material's surface within 1 square meter in 1 hour, when the surface temperature increases or decreases by 1°C under periodic thermal action. The higher the value, the better the thermal stability of the material.
The saying goes: The smaller the heat retention coefficient, the faster it heats up and cools down.
How to Prevent the Peeling of External Wall Insulation
Ensure proper selection and control of thermal insulation materials.
Maintain the quality of materials in the external wall thermal insulation system, including polymer mortar, insulation boards, and anchor bolts. Adhesives should be scientifically proportioned to ensure the polymer content and matching additives; the quality of insulation boards must meet standards, with appropriate measures taken for materials like rock wool, XPS boards, and PU boards, such as reinforcing anchor bolts for rock wool boards and increasing the use of bonding agents for XPS boards to enhance adhesion. When selecting anchor bolts, the type and depth should be based on the type of base wall to ensure the required anchoring force is achieved, preventing the failure of anchor bolt anchoring force and ensuring the anchoring effect is not compromised.
(2) The wall insulation system design is reasonable
Insulation wall projects are a systematic engineering endeavor, requiring consideration of the compatibility between various structural layers. For materials with low self-strength or poor adhesion, it is necessary to design anchor bolts for reinforcement and to improve the bonding rate of the insulation boards. When selecting the exterior finish, it should be matched with the insulation system, ideally designed as a breathable coating system. Flexible tiles should be used for the design of the tiles, and the spacing joints should be reasonably designed.
Enhance construction control
Work as a vulnerable link in the quality control of building wall thermal insulation, it is necessary to conduct a pre-construction inspection and acceptance of the base wall to ensure that the tensile bonding strength of the base meets the specification requirements, the wall flatness is within the controllable range, and there are no phenomena such as hollowing, powdering, and oil stains that affect adhesion. During the thermal insulation construction, it is essential to strengthen the control of construction techniques to ensure the coating rate of the bonding mortar, avoid the improper practices such as false bonding of thermal insulation boards, false hammering of anchor bolts, and dry hanging mesh. Before and after the construction of the thermal insulation system, attention should be paid to weather changes and product protection to prevent the mortar from being washed away by rain or exposed to sunlight before curing.
What are the benefits of exterior wall insulation?
Exterior thermal insulation composite walls refer to walls where the thermal insulation material is placed on the outside of the main structural wall. The advantages of such walls include:
Insulating materials protect the main structure, mitigating significant temperature changes within the walls caused by outdoor climate conditions. These changes occur within the external insulating layer, preventing large temperature fluctuations in the internal main structure, thereby extending the lifespan of the main wall.
The thermal bridge effect, which can lead to excessive heat transfer in localized areas, is effectively mitigated or eliminated when using internal insulation. The thermal bridge effect can cause heat loss, leading to condensation and dew formation, which can damage buildings and impact their lifespan.
The main structure is on the indoor side, with strong heat storage capacity, which can prevent significant fluctuations in room temperature.
During the renovation and construction of exterior insulation for existing buildings, significant interference to residents can be greatly reduced.
Some residents will need to renovate their new homes. During the renovation, the internal thermal insulation is prone to damage, while external insulation can prevent such issues.
External insulation can yield significant economic benefits. Although the cost of external insulation is slightly higher than that of internal insulation, with the adoption of appropriate technology, the unit area cost can be increased minimally.
But due to the increased usable area compared to internal insulation, the cost per square meter of use is actually reduced. Added to this are the benefits of energy savings and improved thermal environment, making the overall benefits highly significant.
Principles for Selecting External Wall Insulation Systems
(1) The principle that the external thermal insulation system has better crack resistance than the internal thermal insulation system.
(2) Layer-by-layer gradient, flexible stress-relief crack-resistant technology principles
(3) The principle that common cement mortar should not be used as the leveling and protective layer material for the surface of the external thermal insulation system.
(4) Principle of increased system stability through the construction without cavities or small cavities
(5) The principle of controlling cracks through the tensile resistance of the protective layer is the main contradiction.
(6) All external thermal insulation systems have been verified for crack resistance principles through large-scale weatherability tests.
(7) Principle of Optimal Selection for Painted Exterior Facade Systems
(8) Ensure thorough consideration of material compatibility and matching principles across all layers.
(9) Enhance Insulation and Sealing Principles at Material Transition Points
(10) Principle of Comprehensive Supply for System Materials in External Wall Insulation System Suppliers
What are Cold Bridges and Thermal Bridges
Warm bridges and cold bridges refer to the same phenomenon, just with different names in the north and south.
A thermal bridge refers to a weak area where heat diffuses from high to low temperatures, typically found at discontinuities in the insulation layer. These areas, also known as the less effective thermal insulation parts of the protective structure, act as bridges for heat to easily pass through, hence the term "thermal bridge."
Cause of Fire in External Insulation Material
Firstly, the lack of sound industry standards leads to varying product quality.
The construction process is lengthy, with numerous hazards on the job site.
The third issue is the high cost of qualified materials, with construction units substituting substandard materials for quality ones.
What's Causing Condensation in Some Rooms During Winter?
Many thermal bridge areas exist in the exterior walls and roofs of some residential buildings.
During winter, condensation or severe condensation occurs on the interior surfaces of thermal bridges such as the inner corners of exterior walls, eaves of the roof, junctions between exterior and interior partition walls, and between exterior walls and floors. This affects the entire gable and roof panels. In walls and cabinets covered by kitchen cabinets, beds, and other furnishings, severe condensation can lead to mold growth. This results in dampness indoors, affecting clothing and grain, and significantly impacting residents' quality of life and health.
Condensation occurs due to insufficient insulation in the protective structure and the presence of significant thermal bridge areas. Under conditions of inadequate heating, low room temperatures, and high humidity, the internal surface temperatures of the protective structure and thermal bridge areas fall below the dew point temperature of the indoor air, causing condensation.
Why Must Insulating Materials Be Moisture-Proof?
Insulation materials are generally lightweight and porous, presenting a structure that is either cellular, fibrous, or powdered, filled with a significant amount of static air. Since air is a poor conductor of heat, this enclosed air provides excellent insulation. However, if the insulation material gets damp, meaning moisture infiltrates its interior, some of the air is replaced by water. Water has a thermal conductivity coefficient over 20 times greater than static air. If the moisture then freezes into ice, the ice's thermal conductivity coefficient is over 80 times greater than static air. Consequently, damp insulation materials exhibit significantly increased thermal conductivity and greatly reduced insulating properties. The higher the moisture content, the more the insulating performance decreases. Therefore, it is essential for insulation materials to remain dry during transportation, storage, and use to prevent dampness.
What is Building Energy Efficiency?
Energy-saving in construction refers to the reduction of energy consumption to the maximum extent possible, under conditions where the same needs or purposes are met, during the production of building materials, construction of buildings and structures, and their use. Specifically, energy-saving in construction involves implementing energy-saving standards, utilizing energy-efficient technologies, processes, equipment, materials, and products during the planning, design, new construction (renovation, expansion), and use of buildings. It aims to enhance insulation performance and the efficiency of heating, cooling, and air conditioning systems, strengthen the operation management of building energy systems, utilize renewable energy sources, and increase the thermal resistance of energy exchange between indoor and outdoor environments, all while ensuring the quality of the indoor thermal environment. This is done to reduce energy consumption resulting from significant heat loss in heating systems, air conditioning, lighting, and hot water supply.
