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MgO SIPs and OSB SIPs are two types of Structural Insulated Panels (SIPs), which are a high-performance building material. The key difference between them lies in the material used for the exterior and interior sheathing, or “skins,” of the panel.

SIPs in general are a composite building material consisting of a rigid insulating foam core (typically Expanded Polystyrene (EPS) or Polyurethane (PUR)) sandwiched between two structural facings. This creates a lightweight, strong, and highly insulated panel that can be used for walls, roofs, and floors.

Here’s a breakdown of the differences between MgO and OSB SIPs:

OSB SIPs (Oriented Strand Board)

This is the most common and traditional type of SIP.

• Sheathing Material: Oriented Strand Board (OSB), which is a type of engineered wood panel made by compressing and bonding together strands of wood with adhesives.
• Fire Resistance: OSB is a wood-based product, which means it is combustible. It can be treated with fire retardants to meet certain fire safety standards, but it will still burn when exposed to fire.
• Moisture Resistance: OSB is susceptible to water damage. If it gets wet, it can swell, warp, and lose its structural integrity. This makes it less suitable for use in high-humidity or wet environments without proper protection.
• Structural Strength: OSB SIPs are known for their excellent structural strength and load-bearing capabilities. The cross-oriented wood strands provide great strength in all directions.
• Cost & Availability: OSB is a widely available and generally more affordable material, making OSB SIPs a cost-effective choice for many projects.
• VOCs: The adhesives used to make OSB can off-gas volatile organic compounds (VOCs), like formaldehyde, which can be a concern for indoor air quality.

MgO SIPs (Magnesium Oxide)

This is a newer, and in many ways, more advanced type of SIP.

• Sheathing Material: Magnesium Oxide (MgO) board, which is a mineral-based sheathing material made from magnesium oxide, magnesium chloride, and other additives. It has a cement-like feel.
• Fire Resistance: This is one of the most significant advantages of MgO SIPs. Magnesium oxide is a non-combustible material, meaning it does not burn or contribute to flame spread. This gives MgO SIPs a superior fire rating and makes them a great choice for fire-prone areas or buildings with strict fire safety requirements.
• Moisture Resistance: MgO board is highly resistant to moisture, mold, and mildew. Unlike OSB, it won’t swell, warp, or deteriorate when exposed to water, making it a better option for wet or humid climates, or for applications like basements or bathrooms.
• Structural Strength: While both are strong, MgO SIPs often have a higher compressive strength than OSB, and they are also impact resistant. They can also provide a solid base for various finishes and cladding.
• Cost & Availability: MgO SIPs are generally more expensive than OSB SIPs. They are not as widely available, though their use is growing.
• VOCs: MgO boards are made from inorganic materials and do not contain organic solvents or harmful chemicals. They are considered to be a “green” building material that does not off-gas VOCs.

Summary Table