How to use VAPOR RETARDERS & BARRIERS in brick, concrete, stucco walls

In my last video we discussed the science of vapor movement, and the perm ratings of different materials. Now we’re going to discuss the location of vapor barriers or vapor retarders in different wall assemblies in different climates. Link to Patreon page:   / belinda_carr   Chapters 0:00 Introduction to vapor retarders 0:16 Vapor retarder classes 0:30 Stud cavity walls 1:22 CMU/concrete walls 2:14 Brick/stone walls 3:20 Stucco walls 3:54 Vapor impermeable walls 4:23 History 5:45 Climate zones 6:28 Air barriers 7:09 HVAC 7:42 Summary Stud cavity insulated walls are the most common construction method in the States. In cold climates, water vapor will travel from the inside out. A vapor retarder must be used on the interior side to limit the movement of water vapor through the wall assembly. Stud cavity insulated walls in warm climates work the opposite way. A vapor retarder must be used on the exterior side. CMU or solid concrete walls. In cold climates, you’d need a vapor retarder behind the drywall since vapor wants to travel from the inside out. In warm climates, you do not need a vapor retarder because concrete acts like one. It restricts the flow of vapor and prevents condensation. Brick or stone walls. These are called moisture storing claddings because they absorb a lot of moisture when it rains. When the sun hits this wet cladding and starts to dry it out, it creates high humidity conditions which drive water vapor to the interior irrespective of whether you’re in a cold or warm climate. This complicates the wall assembly because you have to deal with a two way movement of vapor. To solve this, you must provide a well-ventilated cavity or air gap behind the brick or stone wall to let water and vapor escape. A stucco wall typically consists of a 3 coat stucco on metal lath, a building wrap which acts like an air barrier and vapor retarder, sheathing, cavity insulated walls, and drywall on the inside. The stucco can also be applied directly to CMU walls. This system is similar to the brick/stone wall assembly because it is very vulnerable to water. Another scenario is the use of vapor impermeable insulation like thick XPS, polyiso or closed cell spray foam on the exterior of the building. In cold climates, you must not use an additional vapor barrier on the interior side. The wall relies on vapor drying towards the interior. However, in warm climates, this system works well since it restricts the movement of vapor from the outside to the inside. You also have to comply with certain code requirements that vary depending on the climate zone you live in. In warm climate zones 1,2,3 and 4, the IRC or International Residential Code does not require or prohibit the use of vapor retarders. It’s recommended to use a Class 2 or 3 vapor retarder on the outside of buildings and avoid using Class 1 vapor barriers. In cold climate zones 5,6,7 and Marine 4, the IRC requires either a Class 1 or 2 vapor retarder on the interior side of framed walls to prevent vapor from travelling from the interior to the exterior. Another trend or consensus in the building science community is to prioritize air barriers and stop air infiltration. A study has shown that in most cold climates, over an entire heating season, a 4’x8’ sheet of drywall will let just ⅓ quart of water through by diffusion. But if that same sheet of drywall has a tiny 1 inch by 1 inch hole, moisture-laden air can sneak through and bring in 30 quarts of water! I find this whole discussion of vapor control very interesting because it’s constantly moving. We start a new method of construction or building, then face an unforeseen issue, then invent products to fix that issue, by that time, construction methods have changed again. It’s a constant search to find the ideal building. -------------------- SOURCES: Rockwool graphic: https://www.patreon.com/posts/demisti...    • This water harvester can turn desert air i...   https://www.finehomebuilding.com/2019... https://www.rockwool.com/siteassets/o... -------------------- Fluffy by Smith The Mister https://smiththemister.bandcamp.com Smith The Mister https://bit.ly/Smith-The-Mister-YT Free Download / Stream: https://bit.ly/stm-fluffy Music promoted by Audio Library    • Fluffy – Smith The Mister (No Copyright Mu...   --------------------- Disclaimer: This video was created for educational/informational purposes and qualifies as Fair Use. If you are the creator or own the footage featured in this video and have reservations please notify me via Youtube comments or email and I will accommodate you #buildingscience #permeability #diybuild #permratings #permeance #construction #architecture #design #diy