Housewrap Q & A

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I see there is a lot of confusion over housewraps as well as a lot of misinformation, mostly that has been disseminated by the manufacurers who are only interested in selling their product, not in helping you with good construction practices.

There are a few rules in choosing a housewrap which you should follow, and they all depend on what climate you live in as well.

Without going into all the scientific explanations, here are some general guidelines (if anyone needs further details feel free to e-mail me):

1. Perm Rating - this is the most important issue. In the South, the lower the perm rating the better. My company will not install anything over 15 perms in Florida. Some builders here have made it mandatory that their perm rating be a certain rating or less. Centex for exaample requires their housewrap be 10 perms or less. David Weekley Homes, 15 or less. Air in the south is very humid and the interiors are usually air conditioned, and therefore try to draw that warm moist air into the home. In the Northern cold climates, the opposite is true. So the general rule is, in the south lower perm is better, in the north you want to stick to a higher perm product.


2. U/V rating - all housewraps begin to deteriote as soon as their exposed to sunlight. While the wrap might only be on your house for a few days, you have no idea how long it has sat at the manufacturer or the lumber yard, so make sure it has a good high UV rating. Some have ratings of only 120 days, but some have rating of 365 days.

3. Tear Strength - ALL the manufacturers have different testing methods and will give you the data for whatever type of test their material performed the best at. You've got cross directional, machine directional, trapezoid, blah blah blah. Here's what you do....Get a sample of everything your looking at using from a sales rep or a supplier, just a 12" x 12" piece, and try to tear it. Now, just because you might be able to tear it with your bare hands doesn't make it a bad product, but if it tears to easily, that's a red flag. For overall strength, the cross woven products can't be beat.