Architects work on many different kinds of buildings. But no matter the type of structure, there is an increasing recognition of the need to guard against water intrusion to avoid issues such as mold, rot and insect infestation.
A new generation of housewrap called drainable housewraps provides protection against moisture. As the name implies, drainable wraps incorporate both a water-resistive layer and a drainage gap that helps water drain from behind the cladding at a faster rate.
The drainage channels created by spacers in these wraps give water an unobstructed path to escape from behind the cladding. This path helps eliminate ponding along siding edges that can occur with traditional housewraps. In fact, the newest drainable wraps can be as much as 100 times more effective at removing bulk water from the wall than traditional wraps.
How can you evaluate and choose the best drainable wrap for your project? Here are four questions to consider, according to Tamlyn:
1. Does it meet the code?The International Codes Council (ICC) has an acceptance criteria, ICC-ES AC38, which establishes guidelines for evaluation of drainable wraps. The key test to consider under these guidelines is the ASTM E2273 drainage efficiency test. For this test, water is run through a wall assembly to determine what percentage of it is drained away in 70 minutes. Look for drainable wraps with at least 95 percent drainage efficiency.
2. Is it omnidirectional? Some drainable wraps must be installed in a certain direction to work properly. But omnidirectional wraps work no matter what direction they’re installed, which makes them virtually foolproof. This feature is especially handy when working around odd shapes or bump outs.
3. What’s the climate? The Building Enclosure Management Institute recommends that areas with 20 inches or more in annual rainfall use a drainable wrap. Areas with 40 inches or more should use a full rainscreen system.
4. What are the taping options?Traditional tapes can create a negative overlap and trap moisture that would otherwise drain down and out of the wall. Look for a drainable wrap that uses a double-sided taping system. This system creates a better seal without compromising the shingle-lap fashion install required by codes.