“What Did I Forget?”

Building science has advanced rapidly over the last 10 years, so much so that designing for code-compliant performance and value can be a challenge.

Knowing what to do, and how to do it, with detail design has never been more critical or complex. What do you specify for a wall-to-roof transition? A floor line transition? A foundation-to-wall transition? Is the sequencing correct? What about material adhesion and compatibility? Any oversight can have an adverse effect on project performance and reputation.

There are countless details involved in every building project. Here are just a few ideas to keep in mind on your next one:

Wall Cavity. The wall cavity is where air and water management, thermal comfort, vapor control, fire resistance, acoustic isolation, and structural considerations succeed or fail. Here are general testing standards to reference for each area:

Liquid Moisture.
ASTM E331 Standard Test Method for Water Penetration of Exterior Windows, Skylights, Doors, and Curtain Walls by Uniform Static Air Pressure Difference; ASTM E2112 Standard Practice for Installation of Exterior Windows, Doors, and Skylights.

Heat.
ASTM C518 Standard Test Method for Steady-State Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus; Required Assembly R-values depend on construction type and location and vary by jurisdiction which may be based on IECC, ASHRAE 90.1, and/or ASHRAE 189.1.

Air.
ASTM E2178 Standard Test Method for Air Permeance of Building Materials; ASTM E2357 Standard Test Method for Determining Air Leakage of Air Barrier Assemblies for larger assemblies.

Vapor Moisture.
ASTM E96 Standard Test Methods for Water Vapor Transmission of Materials.

Fire.
ASTM E2307 Standard Test Method for Determining Fire Resistance of Perimeter Fire Barriers Using Intermediate-Scale, Multi-Story Test Apparatus for Perimeters; NFPA 285 for Wall Systems; ASTM E119 for Structural Resistance.

Acoustic.
Sound Transmission Class (STC) for Sound through an Assembly; Noise Reduction Coefficient (NRC) for Sound Reflected/Absorbed in Components; Articulation Class for Acoustic Privacy.

NFPA 285. When combustible materials are to be used in an assembly that is required to be noncombustible, NFPA 285 (Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Non-Load-Bearing Wall Assemblies Containing Combustible Components) is used to determine acceptability. This assembly testing allows for combustible components such as moisture-resistant extruded polystyrene insulation (XPS) or claddings such as metal composite material and high pressure laminate are evaluated in assemblies. Always verify the complete wall assembly for NFPA 285 compliance. This Design Guide can help.

Fasteners. In general, specify a high-quality fastener optimized for the task at hand, such as using an impaling pin with an air and sealing washer to secure mineral wool. For air barriers, gasketing fasteners are best, using the minimum number required and in thermally isolated designs to minimize thermal bridging.

Penetrations. Often the building science fundamentals (thermal, air, vapor, moisture, fire, acoustics) must be weighed against project-specific goals (such as material availability and sequencing) to determine ideal penetration details for each specific situation.

The process of detailing code-compliant transitions should be a careful process that involves the entire project team throughout the project, not just during construction. Owens Corning recommends asking internal or external peers, including our representatives, “What did I miss?“ for a winning, high-performing building. To learn more, visit here.