By Prosoco

R-Guard Air Barrier Systems Stop Air Leakage

R-Guard air barrier systems stop air leakage through wall structures, rough openings, sheathing seams, and material transitions, making your building air tight. And an air tight building is an energy efficient building. That’s why buildings that meet the world’s toughest energy efficiency requirements use R-Guard. An air barrier's expansion and contraction capability is key. All the different materials in your RO expand and contract at different rates. R-Guard’s STPE products contain 98% solids to expand and contract with all those materials and keep air and water from getting into your building.

R-Guard’s STPE Products can be Applied to Damp Substrates

R-Guard’s STPE (Silyl Terminated Polyether) products can be applied to damp substrates and get rained on immediately. Not all polyether products can do this. Using R-Guard takes rain out of the construction schedule.

Developed in the rainy Pacific Northwest, R Guard has been used on many Passive House projects as the primary air and weather barrier. Locally, it's the subject of a study by the independent building science company RDH whichis tracking the performance of Cat 5 + ThermaCork 100% natural cork building facade in Washington State’s wet climate. See more about the study here. Whether you are using R-Guard as a sheathing air barrier, flashing window rough openings, or a full Cat 5 membrane, the process is simple.

General notes and comments:

These are excellent products. The system is durable and non toxic and delivers a high quality seal that retains permeability (18 US Perms) so that layers below can release water vapor as needed. All of the products will stretch and move with the building. Plan on spending some time applying it. Create a smooth base with Joint & Seam Filler and the rest of the layers will go well. If you find more gaps on the way, just add Joint and Seam filler and then re-coat with Fast Flash or Cat 5. It's important to know that ideally, when you are creating a weather barrier, you should cover up all Joint and Seam Filler since the fibrous fillers can transmit water. Each product has it's own distinctive color: Joint & Seam Filler is pink, Fast Flash is a dark red and Cat 5 is brown. So, ideally you would see only red or brown on a weather barrier installation. If you see pink, it's Joint & Seam Filler and should be coated with either Fast Flash or Cat 5.

R-Guard is a family of products intended for use in a system. The STPE formulation gives R Guard a smooth surface that tapes and most other products will not adhere to. This is important to know if you are planning on using a tape to seal windows. We have seen this come up as a surprise in the middle of a project, so it's best to plan on a system approach and use products that will work togther. All of the R Guard family will adhere to the other products in the family. For window installation we recommend R Guard Air Dam for flanged windows, and Hanno Band 3E expanding foam tape for "innie windows" where the application benefits from insulating the gap along with a permeable air and weather seal.

We are always happy to help. Call us with application questions (855) 367-7442.


Learn more at a workshop -  See if there are any upcoming workshops.
Simple Instructions for application of different Prosoco products
Product Coverage Estimator Spreadsheet (Excel) 
Prosoco website


Prosoco products are available in Small Planet Supply’s web store. For more information or to order, go to the store for your country: 

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