C e r t a i n Te e d TECHNICAL BROCHURE
Managing Air & Moisture Flow to Create Comfortable, Healthy Buildings A Complete Approach Whether you are an architect, builder, contractor, distributor or code official, you are being bombarded by countless challenges in the buildings you are helping to create. It is your responsibility to minimize problems (e.g. mold, mildew, etc.) and increase value (i.e.
The ideal road map for mitigating these challenges is to start by incorporating higher standards in product choice and selection for your projects. A great first-step is to focus on the management of air and moisture flow through the building envelope. Smart vapor retarders are able to address both air flow and manage the moisture profile of the exterior wall cavity. This helps to minimize and limit the risk of moisture-based building issues while adding no additional labor.
Water Resistance • These materials are required to withstand bulk water. Common Methods Vapor Permeability • Vapor permeance is a key attribute when considering an air barrier as it affects everything from comfort and IAQ to the energy efficiency of the building envelope. Durability • Physical durability is required for a material to be able to withstand the rigors of the job site and last for the lifecycle of the building.
Managing Moisture: The Challenges of Vapor Retarder Solutions The wall was built tight, so where does the water come from? How does it get in? We all have to accept it at some point—there is no such thing as a waterproof wall. Moisture gets into a wall in many different ways, but it can be narrowed down to two primary types of moisture flow: • Liquid moisture movement • Airborne moisture movement (e.g.
Where does the moisture come from? CONDENSATION RAINWATER LEAKAGE SHOWER PLANTS HUMIDIFIER RAINWATER SATURATION AND SPLASH RANGE LEAKY PLUMBING PERSPIRATION LAUNDRY GROUND WATER STORAGE CRAWL SPACE Moisture can enter the cavity from both indoor and outdoor sources. An average family of four can create two to three gallons of water vapor per day by cooking, bathing, washing dishes and doing laundry.
It’s All About the Potential “Although biological contaminants have been given Traditional poly vapor retarders block moisture in the winter but trap it during the summer. Historically, building codes have classified vapor retarders as having a water vapor permeance of 1 perm or less when tested in accordance with the ASTM E96 desiccant, or dry cup method. Therefore, most products are only evaluated under dry conditions.
Climate Influences Vapor Retarder Selection and Placement In certain climate zones, vapor retarders are mandatory building code requirements, but some may not realize that there are, in fact, sub-categories or Vapor Retarders often called Variable or Smart, as they are able to to adapt to environmental conditions. Four Classes of Permeance Vapor Barrier (Class I) 0.01 6mil Polyethylene (0.05 - 0.06) Semi-permeable (Class III) Vapor Retarder (Class II) 0.1 1 Asphalt Coated Kraft Paper (0.
The Building Climate Regions The America Building America Climate Regions Dry (B) Moist (A) W Marine (C) Cold / Very Cold MT VT/NH ND OR ID MN SD WY PA IA NE IL OH IN KS NM VA KY MI NJ DE/MD WV CO CA AZ MA CT/RD MI NV UT NY WI Mixed-Humid NC OK TN SC AR MS TX AL GA LA Hot-Dry / Mixed-Dry FL Hot-Humid Mixed-humid climates are defined as regions that receive more than 20 inches of annual precipitation, with approximately 4,500 heating degree days and a monthly average
Additional Considerations Cladding Type — Moisture-retaining Claddings According to U.S. Census Bureau 2009 statistics, more than half of all new homes are clad with absorptive materials such as brick, stucco, wood, fiber cement or stone, which are also increasingly prevalent in commercial spaces. These moisture-retaining claddings can worsen moisture challenges in the cavity presented by mixed-humid climates.
What happens next? Mold and Building Product Deterioration Take this a step further. Say you have exterior insulation on your structure and you use closed cell foam with a perm rating of .8 at 2.5" thickness for your interior insulation. You think you are doing the right thing. You have 3.5" of spray foam to meet code, plus you have added the exterior insulation. Well, you have a well-insulated structure but closed cell foam is not smart. It blocks moisture coming and going.
Conclusion MemBrain™ Solves the Air and Moisture Challenges of Mixed-Humid Climates with MoistureSense™ Technology Many in the industry have called for “breathable” walls as a solution to this problem. A slightly more permeable vapor retarder could allow for necessary moisture diffusion. Drying could occur via vapor diffusion in either direction. MemBrain™ is the first-to-market and only such technology available.
Field tests have proven that MemBrain effectively reduces the risk of moisture damage in the building envelope by increasing the construction’s tolerance to moisture load. It is appropriate in cold and mixed climates, but it is not suited for hot climates with high outdoor humidity because it would always be under high, relative humidity conditions. Therefore, it would always be permeable and would not provide vapor retarding benefits.
Glossary of Terms Building Envelope A series of interrelated systems designed to provide comfort and safety to the occupants with a high-degree of energy efficiency Vapor Retarder A material that is used to resist the diffusion of moisture through a floor, ceiling or wall of a building assembly Smart Vapor Retarder A vapor retarder material with the ability to change its permeability based on the ambient humidity condition of its environment Air-Barrier A material that is used to manage the air-leaka
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