Do I Need House Wrap Under New Siding?

Housewrap photo courtesy of the Building Science Corporation

Housewrap photo courtesy of the Building Science Corporation

You may be familiar with housewrap, a common component when building a new home or residing an existing one. Housewrap typically comes in rolls and is installed directly over the structural sheathing, underneath any new exterior insulation or siding added to the wall. If you’re considering building a home or buying new siding, you may be wondering if housewrap is necessary for you. Let’s first take a closer look at what housewrap is and the purpose it serves.

What is House Wrap?

According to the National Association of Home Builders (NAHB), house wrap is one type of weather resistive barrier (WRB) that is placed over the structural sheathing.

Housewraps protect the wall system from bulk water, such as rain, on the exterior of the home. At the same time, housewraps allow water vapor that is generated within the home to pass through, instead of trapping it in the wall and potentially causing mold and mildew problems.

How Do Housewraps Work?

It may be hard to believe that housewraps are able to keep out liquid water while simultaneously?allowing water vapor to pass through. When water molecules are in their liquid from, they group together and actually act as larger molecules. When water is in vapor form, it is actually individual water molecules. The tiny holes in housewrap are large enough to let the vapor molecules pass through, while at the same time blocking the larger grouped molecules.

When properly sealed, some manufacturers claim that their housewraps also reduce air infiltration, which can help save energy and improve the indoor comfort level of a home.

Do I Need a Housewrap?

Installing housewrap on a new home or new siding job has become a customary practice for many builders and remodelers. At Progressive Foam, we recommend the use of a housewrap under any of our siding insulation products as a best practice, although not all exterior replacements or local codes require them. If a need for housewrap is present, using Progressive Foam insulation does not eliminate that requirement. However, because every home situation is different, your local siding installation professional is the best resource for a recommendation that is customized for your home.

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