Air barrier tie-ins: A critical element for successful air barrier application

by tanya_martins | September 19, 2024 1:36 pm

By Iltaz Alam and Marysusan Couturier

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Ensuring a building’s durability and energy efficiency hinges on a continuous air barrier throughout the building enclosure. Critical are the tie-ins between different components and materials, which must be properly managed and installed to prevent failures. This article emphasizes the importance of designing effective tie-in details and ensuring material compatibility to protect the building’s envelope. By following best practises, contractors and specifiers can ensure that all materials work together seamlessly, maintaining the building’s integrity and functionality over time.

By understanding the challenges and following best practices, such as ensuring material compatibility, detailed planning, and rigorous quality control, contractors, developers, and specifiers can ensure their air barrier systems designs are effective and durable. Properly implemented tie-ins enhance the energy efficiency and longevity of buildings and ensure the building envelope acts as one system.

Understanding air barriers

Air barrier systems are designed to minimize air exfiltration and infiltration in the building envelope. Many air barrier materials can also control liquid water intrusion. Depending on the building location and design, air barrier materials can be selected to minimize water vapor transmission or allow passage of water vapor. They are crucial for maintaining energy efficiency, preventing liquid water infiltration, and enhancing indoor air quality (IAQ) by minimizing water accumulation within the wall cavity

Importance of air barrier tie-ins

Tie-ins connect wall air barriers and other building components such as windows, doors, roofs, horizontal decks, and foundation walls. These transitions are critical because they are potential weak spots where air and water can penetrate if not properly sealed. Properly designed and installed tie-ins ensure the air barrier system is continuous and effective throughout the structure’s life.

Challenges in air barrier tie-ins

Common issues with waterproofing tie-ins at below-grade and horizontal deck transitions include planning misses, improper flashing installation, seam and joint openings, and material compatibility issues. Additionally, there is often a lack of protection for overhang tie-in materials and insufficient overlapping layers, all of which can compromise the effectiveness of the waterproofing system. To ensure the durability and effectiveness of the below-grade waterproofing tie-ins, choose compatible materials, design water-shedding laps, and ensure proper planning with horizontal deck application and adequate protection of overlapping layers.

One of the biggest challenges is an airtight and watertight transition between different materials and components. This is complicated by the varying properties of these materials, which can include differences in chemistry, thermal expansion, movement, flexibility, and adhesion characteristics. Additionally, construction tolerances and work quality can affect the integrity of the tie-ins, making rigorous testing and a proven compatibility assurance track record essential.

Materials in contact with each other in the building enclosure must be compatible. Chemical compatibility means the chemistry of one material will not damage the other. Adhesion compatibility measures the ability of the two materials to adhere to each other. Physical compatibility requires that materials in contact with each other expand, contract, or move at similar rates with changes in temperature and other conditions or that accommodation be made for differential movement. To ensure the compatibility of waterproofing materials with air barriers during the design phase, manufacturers of various building materials should provide data from compatibility testing. Specifiers should ask for long-term data, such as an aging test to check chemical compatibility or a long-term field track record.

Best practices for successful tie-ins

Ensuring material compatibility

• Compatibility check: Ensure all materials used for tie-ins are compatible to avoid adhesion failures and leaks.
• Avoid chemical interactions: Confirm there are no adverse chemical interactions between different materials. A quick field check may not guarantee long-term compatibility (e.g. chemical interaction).
• Evaluate sequencing: Consider the sequence of application operations:

° Which product will be applied first?

° If using a water-based product, such as a sealant, will the air barrier be applied while it is still wet?

All possible scenarios should be evaluated, as they can have differing results and can impact tie-ins’ durability in the long run.

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Sample A shows high adhesion values initially and after heat aging, whereas sample B shows a 75 percent drop in adhesion after heat aging (Figure 1). This would not be captured by just performing a field compatibility test. Signs of incompatibility can be softening of the product, blistering, or adhesive running. AAMA 713 is a good resource for testing the chemical compatibility of sealants with flashings.

Roof substrate temperature and flashing solutions

The AAMA 711 specification is a standard the American Architectural Manufacturers Association (AAMA) outlines the performance requirements for self-adhering flashing used in building construction. This specification ensures self-adhering flashings are durable, effective at preventing water infiltration, and compatible with various building materials. It includes tests for adhesion, peel strength, and resistance to weathering to guarantee long-term performance and reliability in different environmental conditions. This specification helps assess the performance of flashings and categorizes them into three levels based on temperature resistance, ranging from 50 to 80 C (122 F to 176 F).

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• Roof substrate temperatures can easily exceed 76 C (170 F), and not all flashing solutions are designed to endure such heat. Accurately predicting rooftop surface temperature extremes is valuable. Roofing surfaces can become extremely hot due to climatic conditions, indoor design, direct solar radiation, and radiative heat transfer with surrounding objects. Factors such as roof surface color, the position and color of adjacent surfaces, and the thermal properties of materials significantly influence peak roofing system temperatures. Theoretically, adjacent parapet walls and metal coping covers may experience similar temperature conditions. Therefore, selecting a high-temperature flashing solution for these tie-in conditions is essential to ensure durability and performance. It is also important to know the temperature exposure of the roof and choose a flashing that matches that specific temperature resistance.
• Detailed planning and design are essential for effective tie-ins. This includes creating detailed drawings and specifications outlining how transitions should be handled. This helps avoid confusion on the “under/over matrix” and ensures consistency during installation.

Interaction with a variety of waterproofing material, tie-in can be with foundation waterproofing or with horizontal deck waterproofing. These waterproofing materials may vary according to specifications and design.

• Proper installer training and rigorous quality control procedures are essential to ensure tie-ins are installed correctly. This includes understanding the specific requirements of the materials used and the conditions they will face in the field.

° As field conditions vary from project to project, correlating laboratory test values to field results is difficult. Project environmental factors such as substrate conditions, operators, testing equipment, adhesives used, material type of dollies, cure times, conditions during cure and testing, etc., will impact the test and cause variance in the results. It is crucial to correlate field test results, which account for these variances, with laboratory tests that show compatibility. This correlation is essential when designing tie-ins.

° Adhere to the specified design guidelines and installation sequence.

° Ensure all overlaps are positioned to shed water effectively.

° Make sure all termination bars and fasteners are correctly sealed to prevent leaks.

° Roll all overlaps thoroughly to ensure a secure bond at critical tie-in areas.

° Some projects specify third-party field testing of in-place air barrier systems as part of a quality control (QC)/quality assurance (QA) process to verify the installation, including tie-ins.

° Ensure all documentation verifying material compatibility is in place.

Application temperature

° Various products and technologies require different application temperatures.

° Installers should strictly follow the manufacturer’s guidelines for both application and storage temperatures of the materials used.

° Make sure the job site conditions meet the recommended temperature and humidity conditions to ensure optimal performance and adhesion of tie-in materials.

Surface preparation

° Ensure all surfaces receiving tie-in treatments are thoroughly cleaned and properly prepared.

° When ending adjacent waterproofing or air barriers, plan for future tie-ins according to the design specifications. For example, if below-grade waterproofing is being terminated for a future tie-in with an air barrier, ensure the overhang of the below-grade waterproofing material is protected from UV exposure, construction debris, and damage.

Recent advancements in both types of products have improved compatibility between waterproofing materials and air barriers. For example, flexible metallic facer (such as aluminum) and advanced adhesive-backed air barriers are compatible with a variety of sealants, coatings, and adjacent materials and can also withstand high heat.

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Conclusion

Air barrier tie-ins are a critical element of a successful air barrier system. Specifiers can ensure their air barrier systems are effective and durable by understanding the challenges and following best practices for material compatibility, detailed planning, properly designed tie-ins, and quality control. Properly implemented tie-ins enhance the energy efficiency and longevity of buildings and contribute to better IAQ and overall building performance.

Authors

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Iltaz Alam, a product manager with GCP (a Saint-Gobain company), is a chemical engineer with more than 14 years of experience in the building envelope field.

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Marysusan Couturier, R&D manager at GCP (a Saint-Gobain company), has more than 25 years of experience in polymer science and owns several patents.

Source URL: https://www.constructionspecifier.com/tie-ins-in-building-construction/

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