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Understanding Air and Vapor Barriers INSIDE your House

Where and when do you need vapor barriers? In this video, Matt Risinger, master builder, answers all of the compelling questions concerning vapor barriers. Filmed at the SIGA headquarters in Switzerland, SIGA produces products, many going into passive houses built to some of the highest standards globally. There are four elements of nature to control when building. Water, air movement, vapor and thermal. Risinger gives us an overview of each one. Vapor, important to this video, moves in two ways, through our walls--diffusion is one method. How much water can actually move through a material via diffusion? Using a diagram, Risinger shows us a 4 x 8 sheet of drywall and a 4 x 8 sheet over the course of one winter," how much water can diffuse? Approximately a third of a quart might diffuse through a wall. We want to stop that water diffusion. What about air moving through the same 4 x 8 sheet of drywall?. What if there was a 1" x 1" hole in that drywall. We have many penetrations in walls, so this is reasonable. How much water will go through compared to diffusion? Instead of a third of a quart it's actually 30. Imagine 30 bottles of water dumping into your wall over the course of a heating system. Curbing this air movement is in some respects is more important than the vapor barrier. All of that water accumulates in our framing. What SIGA is doing is using a very cool high-tech membrane for vapor but also doing all the details right from an air sealing perspective. Regarding the installation of a directional vapor control layer this product is called Majrex. Patrick Hockey from SIGA relates the company's vision—a world of zero energy loss buildings. Each building needs a high-performance envelope. SIGA produces high-performance tapes, adhesives and membranes for building envelopes. They produce the product themselves on their own self-innovated machines and train installers. SIGA employees 500 people, with 260 of them working in the field in training, advice, sales, workshops. SIGA gathers information in its rD; department and develops products specific to the demands. SIGA adhesives are different. For example, there's an adhesive that's a water-based acrylic glue that is etching resistant. It needs to be solvent free, free of VOCs.