By Jean Sealey
Northeast Florida Builders
Association
In today’s market you have several options for the exterior siding of your new home. You can choose brick, stone, stucco, vinyl, cedar and fiber-cement siding. Most of the time, cost is the deciding factors for most new homeowners.
The exterior of your home is the first line of defense against air and water intrusion into the home. When you build a home you must start with the assumption that water and moisture always will penetrate walls, says Bruce Peters, CSI. Peters is a DuPont Tyvek Products Specialist, PPW/DuPont Tyve Weatherization Systems. He also serves on the Northeast Florida Builders Association 2004 Executive Committee as third vice president.
“Whether from inside sources or from outside weather conditions, water and moisture inevitably find ways to get inside walls,” Peters said. “A forgiving wall is one that is able to manage water and moisture, increasing the capacity of the wall to dry out before damage can occur.”
Wrapping a home with a housewrap forms a protective envelope, and is a good building practice that helps combat a home’s worst enemies: water, moisture and air infiltration. A housewrap is your ideal secondary defense against the damaging effects of weather.
Keep in mind, though, Peters cautions, not all house wraps are created equal.
You will need a specially engineered protective material that is highly water-resistant. Rain will get beyond any type of exterior siding or masonry, but rain should not be able to penetrate the housewrap.
Several types of housewraps are available today.
One type is a non-woven material made from extremely fine continuous high-density polyethylene fibers that are fused together by bonding. This type of structure is not susceptible to property loss inflicted by stresses in any direction. No holes are punched through this product to permit moisture vapor breathability. The fibrous structure is engineered to create extremely small pores, which readily allow moisture vapor to evaporate but are so small that liquid water and air have a very difficult time penetrating.
A second type of housewrap is made starting with coarse woven polyethylene slit film. To improve air resistance, a thin film of polyethylene is coated over the weave, which seals the breaks and locks the weave in place. At this stage of the manufacturing, the product becomes a vapor barrier. The product is subsequently pin perforated with holes allowing it to breathe a small amount of moisture vapor. As with all perforated housewraps, there is always a trade-off between air resistance, water resistance and moisture vapor breathability
Another type is a laminated housewrap consisting of a layer of nonwoven fabric, known as CLAF and a delicate, easily damaged microporous film. The lamination of the film to the fabric does not result in a continuous, fused sheet, but the film is necessary to give this product its performance properties. Standard construction practices, such as stapling, moving ladders or wrapping outside and inside corners can damage the microporous film layer exposing the sheathing beneath the product.
A fourth type commonly is used for stucco or brick will not provide a 100 percent barrier. This product can absorb water, hinders stucco curing process, can cause stucco to dry prematurely reducing strength, can move under stucco and cause cracking. It expands when exposed to water and can hinder water drainage. It has lower breathability than some of the other types, and it tears and punctures easily. It also can degrade over time when water is absorbed, and unfortunately, it can’t be repaired with tape. It loses substantial strength when wet and has lower air infiltration protection.
Peters offers this simple test to determine what type of housewrap your builder is using.
First cut a small sample of the housewrap and lay it on a flat surface. Take a quarter and with the edge of the coin scrape it across the surface of the housewrap. If it is a coated product the delicate microporous film is easily removed. Then take the sample of housewrap and place it over the opening of a mason jar filled with water. Replace the screw cap without the center lid and then turn the jar upside down. Pin-perforated products lose the ability to hold out bulk water
“Do your homework and learn all you can about the type of wrap between your home’s interior and exterior surfaces,” Peters suggests. “Choosing the correct wrap for your home will help you build a healthy, energy-efficient home.”