Cross Laminated Timber (CLT)
Description:
Building Material Category: Boards, Panels and Planks
Building Component Type: Wall, Roof, Fenestration-Frames and Floor
Alternative for Conventional Building Material: Traditional construction materials like concrete, steel, and conventional timber framing.
Introduction: CLT is made by layering timber boards at cross angles and bonding them with adhesive. This cross-laminated construction enhances the mechanical properties of timber, making it suitable for large-scale, multi-storey buildings. It is prefabricated in panels that can be quickly assembled on-site. It is a type of engineered wood product that has gained popularity for its sustainability and structural performance. Here’s a detailed overview. It is a type of mass timber used for constructing structural elements such as walls, floors, and roofs. CLT excels over concrete and steel with its sustainability, strength, speed of construction, thermal insulation, aesthetic flexibility, fire resistance, and reduced environmental impact, making it ideal for modern and efficient building projects.
Composition: It is made from multiple layers of solid wood boards (typically softwood or hardwood) arranged perpendicular to each other and bonded with structural adhesives. The timber boards used are softwood or hardwood lumber boards, typically oriented at 90 degrees to each other. High-strength adhesives are used to bond the layers together, enhancing structural integrity.
Applicability in Climatic Zone: It is suitable for use across all climatic zones in India, adaptable for various building types and purposes. CLT performs well in cold climates due to its good insulating properties and ability to handle thermal expansion and contraction. In hot climates, CLT can provide thermal mass, which helps in stabilizing indoor temperatures by absorbing and slowly releasing heat.
Use: It is used for load-bearing walls, floors, and roofs in residential, commercial, and institutional buildings, promoting efficient and sustainable construction practices.
Thermal Performance: It offers excellent thermal insulation properties due to its solid wood construction and airtight nature, helping to reduce heating and cooling energy demands. Factors affecting thermal performance are panel thickness, type of wood species used, and moisture content during manufacturing.
Thermal Conductivity: CLT typically has a thermal conductivity value around 0.12 to 0.15 W/(m·K). This indicates good insulation performance compared to traditional concrete and steel.
Thermal Transmittance: The U-value of CLT panels can vary depending on thickness and construction details. For example, a typical CLT wall might have a U-value ranging from 0.20 to 0.30 W/(m²·K).
Reduction in CO2 Emissions: CLT contributes to CO2 emission reductions in several ways: Trees absorb CO2 during their growth. The carbon remains stored in CLT products, offsetting CO2 emissions over the building’s lifetime. The manufacturing process of CLT generally has a lower carbon footprint compared to concrete and steel. Studies suggest that using CLT can reduce CO2 emissions by approximately 25% to 40% compared to conventional materials, depending on the lifecycle analysis.
Salient Features:
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Natural Insulation: CLT's solid wood construction provides inherent thermal insulation, reducing heating and cooling energy requirements in buildings.
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Sustainability: Made from sustainably sourced wood, CLT has a lower carbon footprint compared to concrete and steel, contributing to green building certifications and sustainability goals.
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Strength-to-Weight Ratio: CLT panels offer high strength and stiffness relative to their weight, allowing for efficient structural designs and reducing overall building weight.
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Speed of Construction: Prefabricated off-site, CLT panels enable faster construction times compared to traditional building methods, reducing on-site labor and associated costs.
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Airtightness: CLT structures can achieve high levels of airtightness when properly designed and constructed, improving thermal performance and indoor comfort.
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Design Flexibility: CLT panels can be customized for various architectural styles and building designs, supporting innovative and aesthetic building solutions.
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Fire Resistance: The thick cross-laminated layers of CLT provide inherent fire resistance, forming a char layer that slows down fire propagation and maintains structural integrity.
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Acoustic Performance: CLT's mass and layered construction contributes to good acoustic insulation, reducing sound transmission between rooms and floors.
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Durability: With proper maintenance, CLT structures can have a long lifespan, offering durability and resilience against environmental factors.
Indian Codes:
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IS 883: Code of Practice for Design and Construction of Timber Structures-Provides general guidelines for timber structures but does not specifically address CLT.
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IS 456: Code of Practice for Plain and Reinforced Concrete –While not specific to CLT, understanding concrete codes can help in integrating CLT with concrete structures.
International Codes for:
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EN 16351: Timber Structures – Cross Laminated Timber – Requirements-European standard specifying requirements for CLT including its properties and performance
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ISO 16670: Wood – Determination of Thermal Conductivity-Provides methods for testing the thermal conductivity of wood products, relevant for CLT
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ACI 318: Building Code Requirements for Structural Concrete-While focused on concrete, understanding this code helps in integrating CLT with concrete systems.
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ANSI/APA PRG 320: Standard for Performance-Rated Cross-Laminated Timber--American standard that specifies performance criteria for CLT
Manufacturers:
In India, the production of Cross-Laminated Timber (CLT) is relatively nascent compared to regions like Europe and North America. However, there are several manufacturers and suppliers making strides in this field. Here are some key players:
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IPIRTI: www.ipirti.gov.in
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Greenply Industries Ltd.: It offers engineered wood products including CLT.
Website: Greenply Industries
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Gujarat State Forest Development Corporation (GSFDC): It is engaged in sustainable timber products, including CLT.
Website: https://www.gsfdcltd.co.in/
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National Timber (P) Ltd.: Provides various wood products, including engineered solutions such as CLT.
Website: National Timber
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Simpson Strong-Tie India: Although primarily known for structural connectors, they are involved in advanced timber construction solutions including CLT.
Website: Simpson Strong-Tie India
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Wood Tech: Provides a range of wood and timber products, including engineered timber solutions.
Website: Wood Tech
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Auroville Timber: It is involved in sustainable timber solutions including CLT.
Website: Auroville Timber
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