MARGIN BUILDERS

Drainable housewraps vs. rainscreens

Bincreasingly recognizing the importance of building science-driven design in creating homes that are resistant to moisture intrusion and air leakage. As such, it’s critical that dealers understand the elements of high-performance wall systems and how the products they sell work together.

One of the most essential parts of a well-designed wall system is a drainage plane that allows bulk water that breaches the cladding to drain away and also provides airfl ow to dry out the cavity. That drainage plane is typically created in one of two ways: via a rainscreen or a drainable housewrap. nderstanding the diff erences between the two, and which is most suited for each project, can help your customers make the right product selections.

The Wall System

High-performing walls perform best as a system, so simply swapping out one product type for another could cause the envelope to fail or not live up to its potential. If a project specifi es a rainscreen, for example, switching it out for a drainable housewrap under the assumption that it will do the same thing isn’t advised without examining the potential impact on the other products in the system.

Think of the drainage plane in a good-better-best scenario: A fl at housewrap is good, a drainable housewrap is better, and a rainscreen is best. he primary diff erence is the volume of bulk water than can drain away and the amount of air that can move through the system to eff ectively rid it of moisture.

A rainscreen is the more robust of the options and can be created by at-

BENJAMIN OBDYKE’S HydroGap SA is a self-adhered drainable housewrap with 1mm spacers to create 96% drain effi ciency.

taching furring strips to the housewrap manufacturers recommend or require and sheathing or with a roll-on 3-D certain types or brands of drainable matrix material. Some claddings have housewraps, so ensure your customrainscreens built into the backside of ers specify what the project’s siding the material. The rainscreen creates a requires. capillary break that causes it to drain downward, and also creates a larger air- Product Considerations space for drying. What system your customers should

A drainable housewrap incorporates choose depends on several factors. First spacers onto the face of a traditional is climate: A rainscreen should be one wrap, either via an embossing texture or of the fi rst considerations in wetter rewith physical bumps. A drainable wrap gions like the acifi c orthwest and the releases the pressure that builds up to Northeast, but may not be necessary in drain but doesn’t increase the wall sys- drier areas. tem’s drying potential. Builders will also need to weigh

There are important considerations budget and cladding. With a tighter within the drainable housewrap catego- budget, a drainable housewrap could ry, as well. For example, an embossed be good enough for cladding materials or textured wrap doesn’t create a true like fi ber cement and composites. ut a drainage space, causing friction that rainscreen is a crucial investment under holds a lot of water. A drainable house- wood siding and masonry. Rainscreens wrap with a 1mm space, however, pro- prolong the life of wood claddings by vides greater drainage effi ciency of up to 96%. For these reasons, some siding (Continued on page 13)

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