Updated: Jul 7
WHY EVERY HOME NEEDS HOUSE WRAP
House wrap creates an air and moisture barrier that boosts a home’s energy-efficiency and creates a healthy, comfortable indoor environment. House wrap is a weatherization membrane. It creates a protective envelope against moisture and air infiltration into the wall cavities. A buildup of moisture within a home’s wall cavities is serious because moisture can lead to wood rot (caused by fungi) and costly repairs. High moisture can also cause the growth of mold, which is unhealthy to the occupants of the home. Uncontrolled air infiltration lowers the effective R-value1 of the wall assembly and reduces the air quality and energy-efficiency of a home. To minimize air infiltration and prevent accumulation of moisture within the wall assembly, the design of every home must include house wrap.
WHAT IS HOUSE WRAP?
House wrap is a synthetic and lightweight material that goes over the sheathing and behind the siding (vinyl, wood, stucco, brick, or composite). A home’s first defense against air leaks and water infiltration is the siding or cladding. House wrap is a home’s secondary defense against air and water penetration and is the backup barrier that keeps water off the framing and structural sheathing and stops air movement through the wall cavity. Installing house wrap not only creates a high performing home but helps the home meet the International Building Codes (IBC) minimum requirements for exterior walls. According to code exterior walls shall provide the building with a weather-resistant exterior wall envelope, including a manner to stop water from accumulating within the wall assembly by providing a water-resistive barrier behind the exterior veneer. When properly installed, house wrap protects a home against air and water intrusions. House wrapping a house creates an energy-efficient, healthy, and comfortable home.
HOW TO INSTALL HOUSE WRAP?
Proper installation of house wrap is essential to its performance. Homeowners should hire a professional to install house wrap. Incorrect installation can affect a home’s ventilation and lead to a buildup of moisture in the wall cavities. Also, if house wrap is left exposed to the sun’s ultraviolet (UV) rays at a job site for a length of time, it can photodegrade, discolor, and loss tensile strength and water repellency. After placing house wrap, a professional is more likely to ensure timely installation of siding. Skilled house wrap installers follow several important steps when installing house wrap:
House wrap is typically installed from the bottom of the house up, overlapping the horizontal joints by at least six inches and the vertical joints by at least twelve inches.
Extend the house wrap over the footing top by at least two inches.
The house wrap is secured every 12 to 18 inches with specific stapling nails or nails designed to hold down house wrap material.
Seal all seams with manufacturer recommended tape.
Installation of house wrap around the door or window openings involves a Y-cut from corner to corner in the openings. Then the excess material is folded through the openings and fasten securely.
Correctly installed house wrap increases energy-efficiency, prevents mold and wood rot, eliminates air leaks, provides some insulation value, and makes a home healthy and comfortable. Improperly installed house wrap will cause more problems than it solves. To ensure all the benefits of house wrap, have a professional install it for you.
HOW TO EVALUATE HOUSE WRAP?
When shopping for house wrap for your home, there are seven features, often listed by the manufacturers, to consider: water and air resistance, drainage, UV inhibitors, tear strength, temperature resistance, and vapor permeability.
Water Resistance: Three tests are used to measure a house wrap’s water resistance. ASTM D779 (boat test), CCMC 07102 (pond test), and AATCC Test Method 127.
Air Resistance: House wraps should have high levels of air resistance. Air barrier materials should be in accordance with IRC Section N1102.4.1 and IECC Section 402.4 and 502.4.
Drainage: A house wrap must effectively drain water.
UV Inhibitors: The maximum time a house wrap can endure exposure from the sun before becoming damaged is an important consideration is selecting house wrap.
Tear Strength: Two tests measure a material’s strength or resistance to tearing: ASTM D5034 and ASTM D882.
Temperature resistance: AC38 Section 3.3.4: (Cold Mandrel Bend Test) ensures the material won’t crack at low temperatures.
Vapor Permeability: The ASTM E96 test measures how much water vapor will pass through a substance in a 24-hour period. The standard mandates house wrap with five perms or higher. The larger the number, the more permeable the material.
Installing house wrap on a home will save money and energy. It will also create a healthy and comfortable indoor environment.
1The effective R-value of a home’s wall assembly is a measure of its resistance to airflow. The effective R-value includes all the materials used in its construction: the drywall, studs, fiberglass batts, plywood or OSB sheathing, water control plane, and siding. The lower the R-value, the higher the conductivities of the wall assembly and the more susceptible a wall assembly is to air infiltration.