INDUSTRY EDUCATION ECHNICAL RESEARCH
INDUSTRY EDUCATION
Illustrated Guide – Achieving Airtight Buildings
Description This guide consolidates information on achieving airtightness in buildings, with a specific focus on larger or more complex building types. Various jurisdictions are working to implement airtightness performance and testing requirements. This guide is intended to be an industry resource with respect to designing, building, and testing airtight buildings, while not compromising other aspects of building enclosure performance, including moisture management, thermal performance, and durability. The information included in this guide applies mainly to mid- and high-rise (Part 3) wood-frame and noncombustible residential buildings within British Columbia. However, it is also applicable for larger or more complex low-rise (Part 9) wood- frame residential buildings and buildings with other occupancies. PRINCIPLES OF DESIGN AIR BARRIER APPROACHES MATERIAL SELECTION DETAILING INTERIOR COMPARTMENTALIZATION MECHANICAL DESIGN PHASED OCCUPANCY All materials, components, and accessories making up the air barrier system must be able to prevent air flow. This is typically defined by building codes as an air permeability less than 0.02 L/s · m 2 (0.004 cfm/ft 2 ) at 75 Pa. Continuity Continuity is the single most important criteria for an effective air barrier system, but also one of the most challenging. Designers and contractors must ensure continuity of the air barrier is achieved around penetrations, transitions, and interfaces in the enclosure. The system must completely enclose the space. Durability The air barrier system must be designed to last for the entire service life of the building or of the materials that cover it. To do so, it may be necessary to regularly maintain sealants or other components of the system, which should be designed to be easily accessible. The system should resist mechanical forces, UV exposure, moisture, chemicals, and other contaminants, throughout the life of the building. Interfaces in particular should be designed to be resilient and be able to accommodate the expected deflections, for example at floor slabs. The durability of the enclosure system itself is important. Air barrier selection must account for vapour movement within the system and exterior moisture loads. Exterior vapour-impermeable membranes may risk trapping moisture inside the assembly. Air barrier materials used as the water resistive barrier must be appropriately installed to provide the necessary protection from moisture loads. See Further Reading in Additional Resources on page 43 for more guidance on assembly durability and vapour/moisture management. Strength and Stiffness From construction to occupancy, the air barrier system must resist forces acting on it. The design should account for mechanical forces such as those created by wind and stack effect pressures as well as allow for dimension l changes in the structure caused by thermal expansion and moisture absorption. A combination of fasteners, tapes, sealants, strapping, exterior insulation, or fully adhered products may by used to achieve this requirement. PRINCIPLES OF DESIGN 2 | DESIGN The design of an effective air barrier system requires materials, components, and accessories that can be combined to control air leakage. While relatively straightforward to achieve in the field of an assembly, ensuring continuity of the air barrier at interfaces and penetrations of the building enclosure is critical to the air barrier performance. An effective air barrier should have the following features: Air Impermeability
Multiple high-powered blower fans installed in a door opening
Status: Guide available online at www.bchousing.org Partners: City of Vancouver, BC Hydro Audience: Builders, architects,
12 | Illustrated Guide – Achieving Airtight Buildings
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Impact The Illustrated Guide – Achieving Airtight Buildings will help developers, builders and designers understand their respective responsibilities in building airtight buildings, ensuring that more buildings will be airtight, which is a key strategy to achieve energy efficiency and durability in buildings.
engineers, professionals in the building development, design and construction industry
58 HOUSING RESEARCH & EDUCATION PROJECT HIGHLIGHTS | JULY 2021
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