Breathable Membrane Under Rafters

Installing a breathable membrane under rafters is one of the most critical steps in creating a durable, energy-efficient building envelope. While traditionally associated with roofing, this technology is equally vital for vertical structures. In fact, the same principles that protect a roof apply directly when using a breathable membrane for walls, creating a continuous shield that blocks wind and rain while allowing internal moisture to escape. This dual functionality makes it a non-negotiable component for modern construction, preventing the "sweating" that leads to rot and mold.

This versatility extends beyond residential lofts. In commercial retrofits, applying a breathable membrane for walls over existing masonry before adding cladding prevents trapped dampness from ruining new finishes. Whether protecting a roof slope or a vertical facade, the membrane ensures the building "breathes" correctly. It is a simple yet powerful solution that safeguards your investment, maintains thermal efficiency, and ensures a healthy indoor environment by actively managing moisture flow in every direction.

Feature	Specification	Core Benefits / Description
Dimensions	Width: 1.0 m / 1.5 m	The 1.5m width significantly reduces horizontal overlaps on roofs, speeding up installation and minimizing leak risks. The 1.0m width is ideal for narrow spaces or small shed repairs.
	Roll Length: 50 m / 100 m (Customizable)
Material Structure	Base: 100% Virgin Polyethylene (PE) + Microporous Breathable Film	Multi-layer co-extrusion using no recycled materials. PE base provides exceptional flexibility in cold weather and superior resistance to acids/alkalis compared to PP, ensuring long-term durability.
	Weight: 80g/m² – 150g/m² (Optional)
Waterproof Performance	Hydrostatic Head: ≥ 2000mm H₂O	Effectively withstands heavy rain, snow, wind, and hail. Prevents liquid water from penetrating insulation or timber frames, ensuring the roof interior stays dry in harsh weather.
	Description: Superior Surface Water Repellency
Breathability	Water Vapor Resistance (SD Value): ≤ 0.02m – 0.05m	Extremely low vapor diffusion resistance. Acts as the building's "breathing skin," rapidly expelling indoor humidity to prevent condensation, mold growth, and timber rot.
	Moisture Transmission: ≥ 1500 g/m²·24h
Physical Strength	Tensile Strength: MD ≥ 180 N/5cm, CMD ≥ 130 N/5cm	High-toughness design withstands temporary foot traffic during construction, strong wind loads, and structural thermal expansion/contraction without rupturing.
	Tear Strength: ≥ 25 N (Trapezoid Method)
Weather Resistance	UV Stability: Safe for Exposure for 2–3 Months	Can be safely exposed to sunlight for 2–3 months before installing outer cladding (tiles/metal) without degrading or powdering. Provides ample buffer for construction schedules in extreme cold or heat.
	Temperature Range: -40°C to +80°C
Safety & Eco-Friendliness	Non-Toxic, Odorless, Asbestos-Free	Green building material with no harmful emissions during production. Safe for occupants; select models are recyclable.
Installation Accessories	Specialized Breathable Waterproof Tape / Fixing Nail Washers	Used with dedicated accessories to ensure airtight and watertight overlaps, creating a complete, continuous protective system.