While there are many factors that go into choosing the best housewrap for your project, there are key elements that must be considered first and foremost. Listed below are the five top performance factors that should be reviewed when picking the right house wrap for the job:
MVTR, or Moisture Vapor Transmission Rate, measures the amount of “water vapor” that can pass through a housewrap over a 24-hour period. Some housewraps have a high perm rate, while others have a low perm rate. With regard to the various wall systems used by builders, it is important to have housewrap options that can meet any perm level required by the builder or architect. Although the primary purpose of any housewrap is to serve as a secondary water and air barrier behind the wall cladding, water can eventually find a way behind the wall cavity through cracks and crevices of the outer wall – this water will need to have the capability to “breathe,” or transfer to the outside without being trapped. Trapped water and moisture behind the wall cavity, of course, leads to mold and rotting.
Construction sites can be very tough environments, and housewrap products in a given project must be tough enough to withstand the rigors of installation. A housewrap that tears easily during installation or does not hold up to wind can cause a builder anxiety and re-work. You should choose a housewrap that has good tear strength and reinforcement, which allows for a worry-free installation. Ultra-violent protection is also important, as housewraps are typically left exposed for up to 4 months.
A main feature of all housewraps is to keep bulk water from entering the wall cavity. Of course, the wall siding, or cladding, is the first line of defense against water intrusion; however, water eventually will find its way around the exterior wall siding and to the housewrap. Many housewraps have hole perforations, which put them well beyond the perm level (5 Perms) required for code approval; however, these perforations also allow bulk water to pass right through to the OSB (or plywood siding). The ability to stop bulk water from passing through is a very important feature to look for in housewrap options.
As discussed previously, bulk water in some form will always find a way around the exterior siding, or cladding, of buildings. Although only a few areas in the U.S. mandate a drainage plane on housewraps, it is always a good practice to use one that includes such a feature. No matter if you are in an area that receives a high volume of rainfall or one that receives little, every location from time to time will have that strong, wind-driven rains that allow bulk water to creep behind the siding. Having a housewrap with a drainage plane feature allows for bulk water to drain down the wall to the weep holes and away from the house. This drainage feature keeps bulk water from “pooling” against the inside of the siding and eventually finding a path inside the wall structure.
Last but not least, any housewrap must serve as a solid air barrier behind the exterior cladding. Non-perforated housewrap products perform the best with this feature, since there are no perforations or holes that allow air into the home. To be considered an air barrier product, housewrap materials must pass ASTM-E 2178 and are required to be < .02 cfm/sq/ft.@1.57psf.
The bottom line is that there are many key features that are needed for any housewrap to perform like they are meant to perform. Please review our website to understand how the JX Alta™ family of housewraps cover them all.