By Bud Coburn
Tyvek® is formed when polyethylene fibers, seven times finer than a human hair, are bonded in a random pattern under high heat and pressure. The resulting product has the following properties:
- high strength-to-weight ratio. While it is strong, Tyvek® can be cut with scissors or other sharp objects;
- water-resistant. Water vapor can pass through, however, making it highly breathable;
- somewhat fire-resistant. Some types of Tyvek® are labeled “Class A,” meaning that they are safe to use in public and private buildings, while other types are labeled the lesser “Class 1” for “normal flammability.” Tyvek® will melt and shrink away from a flame, and it will burn at approximately 750° F;
- chemical-resistant. Due to its neutral pH, Tyvek® is resistant to most acids, bases and salts;
- dimensional stability. Dimensions of Tyvek® sheets remain relatively stable, regardless of temperature or humidity;
- high opacity. As a result of many light refractions between the fine polyethylene fibers and air, very little visible light can pass through Tyvek®; and
- UV resistance. Direct sunlight will degrade Tyvek®, although its life can be extended through the application of opaque coatings.
While Tyvek® is non-toxic and generally harmless, builders should be aware of one lurking danger: static electricity. When Tyvek® is handled, it can generate a static charge unless it is treated with anti-static agents, which are water-soluble and not applied on all Tyvek® products sold. For these reasons, DuPont recommends that Tyvek® — especially Class B, which receives no anti-static treatment — not be handled in flammable or explosive environments.
All Tyvek® falls into one of two categories:
- “hard structure,” which is often known as Tyvek® paper because of its paper-like texture. Hard structure is commonly used to make tents, tarps, waterproof, breathable barriers, and ground cloths; and
- “soft structure,” which is often referred to as Tyvek® fabric because of its fabric-like texture. It is designed for applications where drape and soft feel are important.
Tyvek® is used in an enormous variety of products, from envelopes and wristbands to clothing and tape. Inspectors are most likely to encounter Tyvek® in the following two applications:
- coveralls. These one-piece garments made from Tyvek®, usually white in color, are usually worn by inspectors working in areas where they may come across rodents, lead dust, asbestos or chemicals, especially in crawlspaces. Mechanics also commonly wear Tyvek® suits to avoid contact with oil and fuel; and
- housewrap. Builders install this barrier so that when moisture penetrates the cladding, it will meet the housewrap and drain away before the sheathing absorbs it, where it can cause decay. Housewrap also prevents air infiltration.