Roof Vapor Retarders- FR passes NFPA 701 Large Scale, ASTM E-84
Does Your Roof Need A Vapor Barrier?
A roof vapor retarder (roof vapor barrier) is a critical component in ensuring the longevity and durability of the roof system. It is a material installed beneath the roofing system to prevent the diffusion of water vapor through the roof assembly.
Water vapor is naturally present in the air and can penetrate the smallest of openings in a roof system, including tiny gaps and cracks in the roofing material, the decking, or any insulation installed. When the vapor reaches a surface with a temperature that is lower than the dew point, it can condense and cause damage to the roof system, such as rotting of the decking, corrosion of metal components, and the growth of mold and mildew.
A vapor retarder is designed to minimize the amount of water vapor that can pass through the roof system, reducing the risk of condensation and other moisture-related problems. It can be made from a variety of materials, including plastic sheeting, foil-faced paper, or specialized coatings that are applied directly to the roof surface.
The effectiveness of a vapor retarder is measured by its permeance, which refers to the ability of the material to allow water vapor to pass through it. A lower permeance value indicates a more effective vapor retarder. Please review the products presented on this page to decide what vapor barrier will best suit your environment.
The installation of a vapor retarder is typically recommended in cold climates, where warm, moist air inside a building can come into contact with a cold roof surface and create condensation. However, it may not be necessary in warm, humid climates where the opposite can occur, and the vapor retarder could trap moisture within the roof system.
In summary, a roof vapor retarder is a critical component in preventing water vapor from entering the roof system, minimizing the risk of moisture-related damage and ensuring the longevity of the roof system.
What is the advantage of using a string reinforced vapor retarder linked below on a roof versus a 6 mil film?
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Increased Strength: String reinforced vapor retarders have a layer of polyester scrim or mesh embedded between two layers of polyethylene film. This reinforcement increases the strength and tear resistance of the material, making it more durable and able to withstand construction traffic, installation of insulation and roofing materials, and other potential damage.
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Reduced Punctures and Tears: The reinforced mesh or scrim helps to distribute any puncture or tear along the surface of the material, preventing it from spreading and potentially compromising the integrity of the vapor retarder.
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Improved Stability: The mesh or scrim also helps to stabilize the material, reducing the risk of stretching, sagging, or wrinkling during installation. This improves the overall appearance and effectiveness of the vapor retarder.
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Better Adhesion: String reinforced vapor retarders are often treated with a coating that improves the adhesion of the material to the roofing substrate, preventing air leaks and improving the overall energy efficiency of the building.
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Higher Perm Rating: String reinforced vapor retarders typically have a higher perm rating than 6 mil films. Perm rating is a measure of the material's ability to allow water vapor to pass through it. A higher perm rating means that the material is more breathable, reducing the risk of trapped moisture and potential damage to the roof system.
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Better Fire Resistance: Some string reinforced vapor retarders have been tested and certified to meet fire resistance standards, making them a safer option for roofing applications.
In summary, using a string reinforced vapor retarder on a roof offers several advantages over a 6 mil film, including increased strength, reduced punctures and tears, improved stability, better adhesion, higher perm rating, and better fire resistance. These advantages can result in a more durable and effective roofing system, providing better protection for the building and its occupants.
Please click on the product link to visit the product information.
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APPLICATION: Wall, Roof Vapor Retarders & Barriers PRODUCTS: |
BRIEF PRODUCT DESCRIPTION |
Type-65 |
Reinforced high density 3 ply. General-purpose that meets the strength & permeance requirements of most applications |
Type- 85 |
Reinforced high density 5 ply. Offers greater strength & lower permeance for a higher level of integrity in roofing and under slab applications |
Type-105 |
Reinforced high density 7 ply. Extra strength and extra-low permeance needed to meet additional requirements |
Type- 55 FR |
Reinforced 3 ply. General-purpose fire retardant vapor retarder |
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Reinforced 3 ply. Offers Greater strength and lower permeance. Qualifies as a Class 1 building product |
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Type-90 FR |
Reinforced 5 ply. Delivers fire retardancy for applications requiring additional strength and puncture resistance. |
Griffolyn VaporGuard |
3 ply. Combines HDPE/LLDPE & aluminum to provide extremely low permeance for special applications such as radon protection, cold storage, museums & computer rooms |
