What materials are typically used in pre-insulated duct system?
Pre-insulated duct systems combine a structural duct material with integrated thermal insulation, creating a single, efficient unit. The materials used vary by application (residential, commercial, industrial) and performance requirements (e.g., thermal resistance, fire safety, moisture tolerance). Below is a breakdown of common materials, their compositions, and how they differ in performance:
Composition:
Core Insulation: Closed-cell polyurethane foam (R-value: ~4.0–6.0 per inch, depending on density).
Outer Jacket: Aluminum foil, fiberglass-reinforced polymer (FRP), or coated metal (e.g., galvanized steel) for durability.
Inner Liner: Smooth metal (galvanized steel, aluminum) or rigid polymer (e.g., PVC, polypropylene) for airtightness and airflow.
Performance Characteristics:
Thermal Efficiency: Highest R-value per inch among common duct insulations, making them ideal for low-temperature or high-temperature applications (e.g., chilled water lines, hot air systems).
Moisture Resistance: Closed-cell structure prevents water absorption, reducing mold risk (critical in humid climates or HVAC systems with condensation potential).
Strength and Durability: Rigid construction resists crushing and sagging, suitable for commercial/industrial use (e.g., warehouses, hospitals).
Fire Safety: Most PU foams are treated with flame-retardant additives to meet codes like ASTM E84 (Class A fire rating).
Cost: Higher upfront cost than fiberglass-based systems but offers long-term energy savings and lifespan (20+ years).
Common Uses:
Commercial HVAC systems (e.g., rooftop units, large air handlers).
Industrial applications (e.g., process heating/cooling, food storage).
Underground or exposed duct runs requiring high protection.
Composition:
Core Insulation: Phenolic foam (synthetic resin foam, R-value: ~3.5–4.5 per inch).
Jacket/Liner: Aluminum foil, fiberglass-reinforced panels, or composite materials (e.g., gypsum board for fire resistance).
Inner Surface: Smooth foil or polymer liner for low air resistance.
Performance Characteristics:
Thermal Performance: Moderate R-value, suitable for moderate-temperature HVAC systems (e.g., typical residential/commercial heating/cooling).
Fire Resistance: Naturally flame-retardant (meets Class A fire standards without additives), making them preferred in buildings with strict codes (e.g., schools, offices).
Lightweight and Easy to Cut: Phenolic panels are lighter than PU foam, simplifying installation in retrofits or hard-to-reach areas.
Moisture Tolerance: Closed-cell structure resists water absorption, though less durable than PU in high-moisture environments.
Cost: Mid-range cost, balancing performance and budget for commercial projects.
Common Uses:
Commercial buildings with fire safety requirements (e.g., hotels, retail spaces).
Indoor duct systems in moderate climates.
Modular duct systems (panels assembled on-site).
Composition:
Core Insulation: Polyisocyanurate foam (R-value: ~6.0–7.0 per inch, highest among common duct insulations).
Jacket/Liner: Similar to PU (aluminum foil, metal, or FRP).
Performance Characteristics:
Ultra-High Thermal Resistance: Ideal for extreme temperature applications (e.g., cryogenic systems, high-temperature exhaust).
Thin Profile: Achieves high R-values with minimal thickness, saving space in tight installations.
Cost and Availability: Less common in standard HVAC due to higher cost, but preferred in specialized industrial or commercial settings (e.g., data centers, labs).
Common Uses:
Industrial processes requiring precise temperature control.
High-efficiency commercial HVAC systems in cold/hot climates.
