It’s easy for small amounts of water to enter a home’s wall cavity, both during and after construction. When water evaporates it becomes a gas (water vapor) that needs to escape. If the walls can’t completely dry, a home is more likely to experience mold and rot.
A building material’s ability to let water vapor pass through is called permeance, measured in units called “perms.” There are two ways that the American Society of Testing and Materials (ASTM) measures permeance in its E96 test: Procedure A (desiccant or “dry cup” method) and Procedure B (water cup or “wet cup” method).
Here are some common misconceptions about building enclosure performance and the truths behind them:
TRUTH: “Whether a vapor-control material is 5 perms or 35 perms, the drying rate is usually limited by other materials like the cladding,” says John Straube, a principal at RDH Building Science and an associate professor at the School of Architecture at the University of Waterloo in Canada.
TRUTH: “The house wrap industry emphasizes the ASTM E96 Procedure A or ‘dry cup’ test,” adds Straube. “But the test that’s more appropriate for in-service use of wood-framed buildings is really Procedure B or the ‘wet cup’ test. I have a colleague who says, ‘Procedure A measures how much water vapor passes through when there isn’t any water vapor, while Procedure B measures how much passes through when there is water vapor.’”
TRUTH: It defeats the purpose of an air/water barrier if a home’s exterior flashing isn’t done properly. “There are far greater mold risks when sheathing gets wet after the home is occupied than when it’s being built,” says Straube. “If windows leak into the wall, that’s really scary because you can’t see it.”
Learn more about the LP WeatherLogic™Air & Water Barrier system, the latest addition to LP’s portfolio of structural solutions.
The supply of modestly priced starter homes continues to drop nationwide. A recent report by Realtor.com found that the number of homes priced above $750,000 grew 11 percent last year, while the number of starter homes priced under $200,000 fell by 8 percent.Continue Reading
Any building professional will tell you that the quality of a building material is only as good as its warranty. This is why LP Building Solutions created an industry-leading limited warranty for our line of LP® SmartSide® siding products. One that aims to ensure peace-of-mind for builders and homeowners.
While it’s perfectly alright for a jazz musician to improvise, that approach doesn’t always work as well in homebuilding. Architects, specifiers, engineers and product reps spend many hours collaboratively choosing the right materials for each job – and an abrupt substitution to save a few dollars can ironically be very costly in terms of callbacks, design underperformance and even code violations. “Ideally, all parties involved – the architect, builder and developer – have reviewed the spec before it’s final and have agreed on all the products being used,” says Karen Alves, LP Brand Marketing Associate. “That’s because finding an ‘equivalent’ for siding or fire-rated sheathing involves not just the substrate but the codes that the product meets as well.”