A weather-resistant barrier material installed over wall sheathing and beneath exterior siding to prevent water infiltration while allowing water vapor to escape, typically made from spun polyethylene or polypropylene fibers that create a breathable membrane protecting the building envelope from moisture damage while maintaining energy efficiency.

Housewrap is a weather-resistant barrier material installed over wall sheathing and beneath exterior siding to prevent water infiltration while allowing water vapor to escape, typically made from spun polyethylene or polypropylene fibers that create a breathable membrane protecting the building envelope from moisture damage while maintaining energy efficiency. This critical component of the building envelope serves as the secondary line of defense against water penetration, working in conjunction with exterior siding to create a comprehensive moisture management system. Modern housewraps are engineered to be permeable to water vapor while remaining impermeable to liquid water, allowing the wall assembly to dry while preventing moisture intrusion that could lead to structural damage, mold growth, and energy loss.

The primary purposes of housewrap include preventing water infiltration through the building envelope while allowing interior moisture to escape, reducing air infiltration to improve energy efficiency and comfort, protecting wall sheathing and framing from moisture damage, providing a secondary drainage plane behind the exterior cladding, preventing wind-driven rain from penetrating wall assemblies, maintaining the integrity of insulation systems by keeping them dry, and serving as a temporary weather barrier during construction before siding installation.

Material composition of housewrap typically involves spun-bonded polyethylene or polypropylene fibers that create a non-woven fabric, microporous structure that allows vapor transmission while blocking liquid water, UV-resistant additives that provide temporary exposure protection during construction, printed installation guidelines and overlap markings for proper application, and various permeability ratings measured in perms to indicate vapor transmission rates.

Fun Fact: The first housewrap was developed by DuPont in the 1950s as “Tyvek,” originally created for use in medical packaging and protective clothing before being adapted for construction! The name “Tyvek” comes from combining “tie” and “vek” (meaning strong), reflecting its tear-resistant properties. A single roll of housewrap can cover up to 1,000 square feet and weighs only about 25 pounds. Interestingly, housewrap is so effective that it can stop a 55-mph wind-driven rain while still allowing water vapor to pass through at a rate of 50+ perms!