Home Innovation Insights

Don't leave it to chance. Know if your building product is going to allow proper moisture mitigation.

Bob Hill, PE
May 22, 2014

Moisture Testing: An Ounce of Prevention, Better Than a Pound of Cure

In the last decade, as energy efficiency regulations for homes has been ratcheted up dramatically and builders have had to adjust to creating higher performing structures, dealing with excess moisture in homes has become one of the biggest hot spot quality issues builders have had to address. Making houses tighter with less air infiltration creates positive energy benefits but, unless adequate ventilation is provided in the right way, there can be moisture-related issues (aka, mold). Proper moisture testing for building products is crucial to ensure products perform as manufacturers, builders, and homeowners desire.

The opportunity for mold to occur increases significantly when there are leaks that allow moisture intrusion in the building envelope. There have been recent code changes that require the use of weather resistant barriers (WRB) and better flashing around openings (e.g., windows, doors, plumbing, etc.), which greatly reduce water intrusion issues when properly installed … emphasis on that last part, “when properly installed.” Manufacturers continue to introduce new products and builders and trades continue to experiment with various installation approaches for new products. Relying on unproven methods for product use and installation may manifest into big problems for builders down the road. Even a slow leak over a long period of time can cause major issues. And, because these leaks are usually behind the drywall, they may happen for years before the moisture becomes something the homeowner notices. By that time, the fix is usually very costly.

Proper testing is the best way to be sure the products and/or assembly, as installed, are not going to leak. One of the most common test methods used is ASTM E331, which we conduct here at Home Innovation Research Labs. The official name for this test is “ASTM E331 Standard Test Method for Water Penetration of Exterior Windows, Skylights, Doors, and Curtain Walls by Uniform Static Air Pressure Difference,” but we like to refer to it as the Wind-Driven Rain Test. To conduct this type of test, we direct a uniform water spray at the rate of 5 gallons per hour per square foot of surface at the test specimen, using the equivalent of about 25 miles per hour wind pressure for a specific period of time. The time requirement typically varies from 15 minutes two hours.

Home Innovation’s Wind-Driven Rain Test Chamber measures 8 feet tall and 10 feet wide and can easily test most full-size building product specimens and assemblies. Although the test method seems somewhat limited given its code-based name, the basic approach can be extended to pretty much any product or system involved with the building envelope. We’ve tested all types of components and systems, from masonry walls to flashing systems.

Another relatively new approach to mitigating water intrusion is to include a drainage plane between the external wall cladding and the underlying sheathing. The concept assumes that water will get behind the cladding and must be able to quickly drain out of the wall system once it does. And, of course, there is a standard test method for this approach with an equally catchy title – it’s called the “ASTM E2273 Standard Test Method for Determining the Drainage Efficiency of Exterior Insulation and Finish Systems (EIFS) Clad Wall Assemblies.” (Rolls off the tongue, doesn’t it?!) In this test method, we cut a slot 2 inches high by 24 inches long through the exterior cladding and spray water into that slot at a rate of 106 g/min (about 1.7 gallons/hour) for 75 minutes. The test set up catches the water coming out the bottom of the wall via the drainage plane for one hour after the water spray is turned off, and we note the percentage of water drained out of the wall. The idea is to have the wall retain very little water. This test is also pretty flexible, despite the apparent limitations of its title, and we’ve used it to test just about every type of exterior cladding system for our clients.

If you are developing, manufacturing, or using previously untested products or systems to prevent water intrusion, we can help you ensure and demonstrate the product or system works as it’s supposed to. Let us know how we can assist your efforts.

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