4.5 Sandwich Insulation Wall Panel Technology
4.5.1 Technical Overview
The sandwich insulation wall panel—often called the “sandwich insulation wall panel”—is a composite wall panel created by sandwiching insulation materials between two layers of concrete panels (inner leaf wall and outer leaf wall). This design enhances the energy efficiency of external wall insulation, minimizes fire risks, extends the insulation lifespan, and lowers maintenance costs for exterior walls.
Typically, sandwich insulation wall panels consist of inner leaf walls, insulation boards, tie pieces, and outer leaf walls, forming a layered structure. The inner and outer leaf walls are usually made from reinforced concrete, while the insulation boards are generally B1 or B2 grade organic insulation materials. The tie pieces are typically fabricated from high-strength FRP composites or stainless steel.
While sandwich insulation wall panels can be applied to both prefabricated and cast-in-place walls, they are especially suitable for prefabricated concrete exterior walls.
Based on their stress characteristics, sandwich insulated exterior walls fall into three categories:
- Non-composite sandwich insulated walls: Here, the inner and outer concrete layers act independently, making calculation and design straightforward. These are suitable for shear walls and retaining walls in various high-rise buildings.
- Composite sandwich insulated walls: The inner and outer concrete layers share the load, typically used for load-bearing exterior walls in single-story buildings or retaining walls.
- Partially composite sandwich insulated walls: These have a stress state between composite and non-composite types. Their complex stress behavior makes calculation and design challenging, requiring further research on their applications.
Non-composite sandwich wall panels rely on the inner leaf wall to bear the entire load, while the outer leaf wall serves primarily as a protective barrier for the insulation. Slight relative movement between the two concrete layers is possible, allowing the outer leaf wall to relieve temperature-induced stress, preventing cracking, and ensuring the outer leaf wall, insulation board, inner leaf wall, and structural components share the same service life.
In China, prefabricated concrete exterior walls mainly employ non-composite sandwich wall panels.
The placement of insulation connectors within sandwich insulation wall panels must carefully consider stress safety and deformation during production, construction, and regular use.
4.5.2 Technical Specifications
Sandwich insulation wall panels should be designed to match the building structure’s lifespan. The temperature-resistant connectors within the panels must exhibit sufficient load-bearing capacity and deformation tolerance.
For non-composite sandwich wall panels, the design principle emphasizes that the outer leaf wall concrete should be able to release temperature-induced stress through slight relative slip with the inner leaf wall.
Regarding safety factors:
- In regions with seismic fortification levels of 7 or 8, the bearing capacity safety factor should be at least 3.0 when considering earthquake combinations, and at least 4.0 without earthquake considerations.
- In regions with seismic levels of 9 or higher, earthquake combinations must be considered, and the safety factor should not be less than 3.0.
The vertical displacement of the outer leaf wall under its own weight must be controlled within acceptable limits. Additionally, no concrete connecting bridges should penetrate the insulation layer between the inner and outer leaf walls.
The thermal performance of sandwich insulation wall panels must comply with energy-saving requirements. Tie pieces must meet mechanical, anchoring, and durability standards. Both product quality and design applications should conform to relevant national regulations.
4.5.3 Scope of Application
Sandwich insulation wall panel technology is suitable for:
- High-rise and multi-story prefabricated shear wall structure exterior walls
- High-rise and multi-story prefabricated frame structure non-load-bearing exterior wall cladding
- High-rise and multi-story steel structure non-load-bearing exterior wall cladding
- Other exterior wall types used in various residential and public buildings
4.5.4 Engineering Examples
Notable projects employing this technology include:
- Beijing Vanke COFCO Holiday Scenery
- Tianjin Vanke Dongli Lake Project
- Shenyang Metro Development Company Phoenix New City
- Shenyang Metro Development Company Huisheng Community and Huimin Community
- Beijing Guogongzhuang Affordable Housing Project
- Beijing Jiugong Affordable Housing
- Jinan West District Jishui Shangyuan 17# Building
- Jinan Gangxingyuan Affordable Housing
- China Construction Technology Wuhan Xinzhou District Yangluo
- Shenzhen Hong Kong New City
- Hefei Baoye Runyuan Project
- Shanghai Poly Real Estate Nanda Project
- Changsha Sany Affordable Housing Project
- Leshan Huagou Office Building
- Tianjin Yuanda Beijing Innovation Base Public Rental Housing
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