Technology Guide
How Does a Waterproof Breathable Membrane Work in Wall and Roof Systems?
Waterproof breathable membrane principle for housewrap, WRB, roofing underlayment and building-envelope applications.
KOSITE is an Indonesia-based manufacturer of waterproof breathable membranes, housewrap, water-resistive barriers (WRB), and roofing underlayment for global building-material markets.
A waterproof breathable membrane performs two essential functions:
It blocks exterior liquid water while allowing water vapor inside the wall or roof assembly to diffuse outward.
Rainwater exists as liquid droplets and may be driven against a building by wind. Water vapor exists as gas molecules and moves through vapor-permeable materials because of differences in temperature and vapor pressure.
A properly designed KOSITE housewrap or WRB membrane can help
- Resist wind-driven rain
- Support outward vapor diffusion
- Reduce condensation risk
- Protect insulation and structural components
- Improve building durability and energy efficiency
Vapor permeability is not air permeability
However, vapor permeability is not the same as air permeability. A membrane may allow water vapor to diffuse while still limiting uncontrolled air leakage.
Important properties buyers should evaluate
When selecting a waterproof breathable membrane, buyers and engineers should evaluate more than basis weight. Important properties include:
- Water resistance
- Water-vapor transmission
- Air permeability
- Tensile and tear strength
- Nail-tear resistance
- UV and aging resistance
- Roll dimensions and handling
- Compatibility with tapes, flashings and sealants
Correct installation is equally important. Overlaps, sealed joints, windows, doors, penetrations and drainage paths must work together as one complete building-envelope system.
PT KOSITE NEW MATERIALS provides OEM and private-label manufacturing solutions from Indonesia for
- Housewrap and wall WRB
- Waterproof breathable roofing membranes
- Roofing underlayment
- Facade and building-envelope membranes
- Customized nonwoven and laminated materials
Water out. Vapor out. Build dry. Build durable.
For OEM, private-label or technical cooperation, connect with KOSITE.