So, according to the Building Science Corporation, A vapor barrier is defined as a layer with a permeance rating of 0.1 perm or less., And ACI approaches this a little differently still. It is a thin layer of impermeable materialusually polyethylene sheeting. Membrain closer resembles polyethylene sheeting or 6 mil poly and comes in rolls of 8'4, 9'4 or 10'4 x 50. The insulation materials used to satisfy this option also contribute to but do not supersede the thermal envelope requirements of Chapter 11. How Climate Impacts the Decision-Making Process. A thin, 6-mil vapor barrier can cost as little as $0.15 per square foot, while a thick, 20-mil vapor barrier can cost as much as $0.50 per square foot. This feature has been temporarily disabled during the beta site preview. Anything above 10 perms is defined as a vapor-permeable membrane. The International Residential Code (IRC) defines vapor retarders as Class I, II or III based on how permeable they are to water vapor, the lower the permeability - the less water vapor that will pass through the vapor retarder. A vapor retarder shall be provided on the interior side of frame walls of the class indicated in Table R702.7(2), including compliance with Table R702.7(3) or Table R702.7(4) where applicable. Examples include plywood, OSB, the kraft facing on fiberglass batts, 1-inch-thick XPS foam insulation, and one coat of vapor-retarder paint applied to drywall. This won't delete the articles you've saved, just the list. Table R702.7 (2) also clarifies that Class III vapor retarders are permissible in Climate Zones 1-3 with no special requirements. Class 3 vapor retarders are considered semi-permeable. Class I - Very low permeability vapor retarders - rated at 0.1 perms or less. According to standards like ASTM E1745, vapor retarders must have a permeance rating of less than 0.3 perms. Some examples here include unfaced expanded polystyrene, fiber faced polyisocyanurate, and asphalt-backed kraft paper facing on fiber glass batt insulation. When we start to look at categorizing vapor retarders, materials can be separated into three general classes based on their permeance and are defined in the International Building Code (IBC). From a practical standpoint, a vapor retarder of less than 0.01 perm is effectively a vapor barrieralmost no . TABLE 1404.3(3), 1404.3.3 Exterior Walls, Material Vapor Retarder Class, 20.4.3* General Requirements for Storage, Class III, 1404.3.2 Hybrid Insulation for Moisture Control With Class III Vapor Retarders, Standard for the Installation of Sprinkler Systems 2019 of Illinois, Spray foam with a maximum permanence of 1.5 perms at the installed thickness applied to the interior cavity side of. [3] Furthermore, vapor retarders also are . Vapor barriers bar the transmission of water vapor through walls, ceilings, and floors. Regardless of the term, it is the function of the material that needs to be evaluated to control the entry of water vapor into the building by vapor diffusion. Vapor retarders are commonly used in low-slope roof assemblies to perform two functions: Limiting airflow into the roof assembly. Other examples of this class include plywood and #30 building paper. The effectiveness of a vapor retarder is measured in terms of the permeance of the . The most important location to install a vapor barrier is under a concrete slab. Contact us now. That means that the vapor permeance range . Continuous insulation with R-value 3 over 2 x 4 wall. Sheet polyethylene (visqueen) or unperforated aluminum foil (FSK) are Class I vapor retarders. Typically, a vapor retarder has to have a perm rating of 1.0 or less to be successful. Section 1907.1 of the 2012 IBC calls for 6-mil polyethylene or other approved equivalent methods or materials shall be used to retard vapor transmission through the floor slab.. Each of those sides has differing moisture considerations (which is why you will see different permeance values for different construction materials in the chart below). 2022 W. R. Meadows, Inc.All rights reserved. Latex pain, enamel paint, or other approved materials applied in accordance with the manufacturers installation instructions for a perm rating of greater than 1.0 and less than or equal to 10.0. Helps reduce fungus, mildew, and mold. These materials aren't vapor barriers, but they slow down the flow of water vapor somewhat. The IECC notes, When design conditions exist that promote drying through the use of ventilated claddings or reduce closed cavity condensation potential through the use of exterior insulating sheathings., Ultimately, what is a vapor barrier? It is common to install a vapor retarder on the top surface of a concrete deck. Vapor Retarder Classes and Options (R702(1) and R702(2) The 2021 IRC defines vapor retarder classes, specifying their use in different climate zones: Class I, II, and III. Continuous insulation with R-value 7.5 over 2 x 4 wall. The newly published 2021 IBC and IRC codes include some important advancements to water vapor retarder provisions. Table R702.7(2) also clarifies that Class III vapor retarders are permissible in Climate Zones 1-3 with no special requirements. True vapor barriers are products that have a permeance (water-vapor transmission rating) of 0.00 perms when tested per ASTM E 96., Then, in ACI 302.2R: Guide for Concrete Slabs that Receive Moisture-Sensitive Flooring Materials, it is stated, Historically, the construction industry used the term vapor barrier to describe a polyethylene-based material below a concrete slab. White Paper: Under Slab Vapor Barriers/Retarders, North America: 800.342.5976 Terms of Use, USA Canada Franais Espaol International. A. However, the Kraft paper acts as a Class-III vapor . Continue Learning: One significant consideration still missing from the IRC and IBC water vapor retarder provisions is that the code lacks a means of controlling the vapor permeance on the interior and exterior side of wall assemblies that do not include continuous insulation to control water vapor. "What are the classes of vapor retarders? SARANEX . Continuous insulation with R-value 7.5 over 2 x 6 wall. Vapor retarders can allow some moisture movement, and the last thing anyone wants is to use the wrong vapor-retarding products on walls, roofs, or floors. Stego. support@buildsite.com; 1.888.717.8665 Log In; Find Products . Some examples here include unfaced expanded polystyrene, fiber faced polyisocyanurate, and asphalt-backed kraft paper facing on fiber glass batt insulation. While this may appear to be a lot to digest, it is actually fairly straightforward and effective. For open- and closed-cell spray foams, check manufacturer's specifications. Continuous insulation with R-value 5 over 2 x 4 wall. A vapor retarder shall not be required in Climate Zones 1, 2, and 3. By definition, vapor retarders must pass less than 0.3 perms; the generally accepted definition of a vapor barrier is that it passes less than 0.01 perms. Additionally, these products shouldnt be used on building envelopes with moisture storage claddings, like concrete or brick. The Stego Wrap Class C 10-Mil Vapor Retarder provides protection in a broad range of environments and may also be used in systems for the reduction of soil gas (radon and methane) migration. Class I vapor retarders are sheet polyethylene (visqueen) or unperforated aluminum foil (FSK). Section 1404.3.1 goes on to state "Class I and II vapor retarders shall not be provided on the interior side of frame walls in climate zones 1 and 2. This is an excellent example of how . It is absolutely critical to control and manage the movement of moisture in buildings and structures. An approved design using accepted engineering practice for hygrothermal analysis shall be an alternative. The Class III vapor retarder provisions in Table R702.7 (3) are expanded to apply to all of Climate Zone 4, not just Marine 4 (this applies to the 2021 IBC only). Class I vapor retarders shall not be provided on the interior side of frame walls in zones 3 and 4." Further, Section 1404.3.2 specically states that "Only Class III What is an ASTM E1745 Class A Vapor Barrier Used For? When I first researched paints, as a result of Lstiburek's books . Become a GBA Prime member and get full access to GBA articles, enyclopedia, videos, CAD library, and more. Typical Cavity + Continuous Insulation Wall Assembly. Class I and II vapor retarders with vapor permeance greater than 1 perm when measured by ASTM E96 water method (Procedure B) shall be allowed on the interior side of any frame wall in all climate zones. However, when looking at the current International Building Code (and its derivative codes), there are no specific performance requirements when it comes to under slab vapor protection. What exactly . The vapor retarder class shall be based on the manufacturer's certified testing or a tested assembly. Siga's Majrex used at the code minimum house installed between the attached garage and house. SARANEX CX Vapor Retarder Film and Tape are durable, flexible polyvinylidene chloride (PVDC) jacketing materials for mechanical insulation systems. An Thomas, ASTM E 1745 defines three classes of membranes, A, B, and C, by three physical characteristics. We invite you to reach out to us today to learn more about our product line and to arrange an individualized consultation. These products only reduce or retard water vapor transmission. Stego Wrap 10 - mil Class A Vapor Retarder. . Vapor retarders, while they typically also do have low perm ratings, are still not as low as what is required in a vapor barrier. Class I vapor retarders (non-permeable barrier) have a vapor permeance of 0.1 perm or less. What is a vapor retarder for class 1 or 2? Class I vapor retarder has a 0.1 perm or less. xaC~;lUpu(QYrhA*rg#8qL 4 Rq0!,LQe0;@a%yw&2h A1a. Vapor retarder materials shall be classified in accordance with Table R702.7(1). Continuous insulation with R-value 2.5 over 2 x 4 wall. Sheet polyethylene (visqueen) or unperforated aluminum foil (FSK) are Class I vapor retarders. Vapor retarders are designed to impede moisture flow through the wall assembly and protect the building envelope from damage done by condensation. Figure 2 shows the new 2021 IRC code language for vapor retarders. When used on the interior side as a vapor retarder, they promote inward drying by opening up in periods or seasons where inward vapor drives occur (most prominently during spring and summer months). The Class III vapor retarder provisions in Climate Zones 7 and 8 are differentiated and strengthened to address an inadvertent error in prior codes that treated Climate Zones 7 and 8 the same. The main reason to install an interior vapor retarder is to keep a building inspector happy. Experience by many contractors and some consultants suggest that special low permeance layers such as polyethylene are rarely needed in many types of walls. 0.1 Perm or Less. Legal Notices / Imprint If this assembly is moved to Minneapolis [climate zone 7], a Class II vapor retarder is required on the interior (a kraft paper faced fiberglass batt)." . Examples include stucco, one or two coats of latex paint, 1 inch of EPS foam insulation, and more than 5 inches of open-cell spray foam. . A vapor retarder is a material designed to limit the amount of moisture in the air from traveling through it. The term vapor retarder is still used. While still exceeding ASTM E1745 Class product requirements, Stego Wrap Class C 10-Mil Vapor Retarder provides an economical option for projects. (Asphalt backed, not just plain kraft paper). We need to get away from using the term vapor barrier and vapor retarder and actually define what performance characteristics the material is required to meet based on the actual project requirements. by the inner facing of the foil-faced ISO). The application of the concrete, as well as its mix, can determine permeability. Figure 1. A typical wall assembly of this type is shown in Figure 1. Use of a Class I interior vapor retarder in frame walls with a Class I vapor retarder on the exterior side shall require an approved design. For example, an interior vapor retarder is not required and instead the vapor control layer is provided on the exterior side (e.g. 5.3.5 The type of base material on which the vapor retarder is to be installed. We have created some of the toughest products in the industry and would love to help you understand what vapor barrier or vapor retarder is best for your construction project. For example, within ASTM E1745: Standard Specification for Plastic Water Vapor Retarders Used in Contact with Soil or Granular Fill under Concrete Slabs, a vapor barrier is defined as, A material or construction that impedes the transmission of water vapor under specified conditions.. Class I vapor retarders with very low permeability, rated at 0.1 perm or less. Table R702.7 (2) also clarifies that Class III vapor retarders are permissible in Climate Zones 1-3 with no special requirements.