“What Difference Does It Make” As long as it meets Code?

By: Chris Daniel

How many times in our lifetime have we heard the words, “What difference does it make”?  Many times, we hear that phrase because people either do not understand the differences or do not care to learn more to understand the difference it does make.

When it comes to Weather Resistant Barriers there are a number of different types, from the woven coated fabric to nonwovens with breathable membranes.  Both types “Meet IBC Building Codes”, based on the criteria that has been around since only Felt paper was used as a secondary barrier.

Let’s take a look at several different weather resistant barriers (WRB’s) and help you determine the answer to “What difference does it make”?

First, one of the most common types of weather resistant barriers on the market today is the woven, coated and perforated house wrap.  These products consist of a polymeric woven fabric that is coated with a solid film coating, then pin perforated to allow for breathability.  Although most of these products meet the >5 perm requirement for building code they are forced to “poke” thousands of holes in the material.  Claims are made that these products work as an air and moisture barrier, however, the test that has been “grandfathered in” the codes only require these products to meet the same requirements as 15lb felt, which has minimal water hold out.

The test used in the industry for water resistance with the majority of these perforated products, ASTM D 779, requires the manufacturer to build a “boat” out of the material and float it on a cup of water with a desiccant material inside the boat.  As long as the desiccant doesn’t get absorbed within 10 minutes a Pass grade is given.  This test does not show how this product would stand up to “bulk water” that sometimes gets behind the exterior cladding.  Another factor to consider is the fact that the majority of products will not pass the water column test that non-perforated breathable products do pass.

Additional products offered in the industry utilize either a nonwoven, woven or mesh membrane that is extrusion coated or laminated to a breathable coating or film.  These products range in breathability from 15-60 Perms depending on product and also must pass the AATCC 127 water column test for water resistance.

The aforementioned test consists of taking a beaker of water at 55cm situating it over the fabric.  In order to pass, fabrics must not allow more than 3 drops of water to pass through the material within a 5 hours period.  This test represents how weather resistant barriers would react if bulk water found its way behind a home’s exterior siding.  There are no mechanical “holes” poked in these materials as they use their solid breathable coating or films to keep water out.  Products that are non-perforated and breathable advertise water resistance values typically >250cm based on this test.

Based on how these two different types of products perform, it is easy to understand “what difference it makes” when choosing a weather resistant barrier.

Many argue that all housewraps have holes due to installation, however, non-perforated WRB’s have thousands less than perforated and when installed with plastic cap nails these products perform as they were intended.

For more information, please visit our website at www.jxalta.com to review our family of housewrap products.