What is a weather Barrier?

A house weather barrier, also known as a weather-resistant barrier (WRB), is a protective layer installed on the outside of a house—typically between the sheathing (like plywood or OSB) and the exterior siding. Its main job is to protect the structure from water and air infiltration, while still allowing moisture vapor to escape from inside the wall.

What Is Tyvek®?

Tyvek® is a brand of synthetic house wrap made by DuPont. It’s a protective barrier installed under the exterior siding of a home, usually over the sheathing (plywood or OSB), to protect the structure from air and moisture infiltration while still allowing moisture vapor to escape. Think of it as a breathable shield that helps your house "breathe" — keeping outside water and wind out, but letting interior moisture (like condensation) escape.

The National Building Code of Canda (NBCC) and most provincial codes require a water‑resistive barrier (WRB)—also called a housewrap or weather-resistant barrier—to be installed over exterior sheathing before siding. These layers protect the building envelope by blocking wind-driven rain and reducing air leakage, while still allowing moisture vapor to escape. Tyvek® HomeWrap® is a widely accepted example. To function properly, the WRB must be continuously sealed around windows, doors, corners, and penetrations, and taped or caulked to maintain airtightness.

Benefits of Using Tyvek® on a House

Water-Resistant: Helps prevent rain and moisture from penetrating into the wall cavity
Protects against rot, mold, and mildew by keeping the inside of the wall dry
Breathable: Allows water vapor inside the wall to escape. Prevents trapped moisture, which can lead to structural damage over time
Air Barrier: Blocks drafts and outside air, which improves your home’s energy efficiency
Improved Insulation Performance: When used properly, Tyvek can improve the effectiveness of insulation by reducing air leaks
Durable and Tear-Resistant: Strong enough to withstand weather and rough handling during construction

 Things to Know:

It’s not a water-proofing system: Tyvek resists water but isn't a substitute for flashing or proper siding. Water can still get behind it if not properly sealed at seams and penetrations. It important to install correctly, If not taped, overlapped, or sealed properly, it may not perform as intended. Doesn’t replace insulation: It helps your insulation work better but doesn’t insulate the home by itself.