The presence of an airspace enclosed within a building envelope assembly is known to contribute to the overall thermal performance of the assembly. However, the actual R-value of an airspace can vary significantly depending on various conditions of use, such as the air-tightness of the assembly of materials enclosing an airspace. Also, its effective R-value contribution is generally small in comparison to conventional insulation materials and methods, even when a reflective airspace is used. An airspace by itself, therefore, is incapable of providing adequate, code-compliant thermal performance for modern building thermal envelope assemblies.

Top Resources:

  • ABTG Research Report
  • Educational Program
  • Design Guide
    This guide reviews current technical knowledge and regulatory requirements to assist the designer in R-value characterization and limitations of use for airspaces within building assemblies for code compliance.
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Tools & Education
Description

Joe Lstiburek provides grounding insight on the do’s and don’ts of thermal resistance compliance.

Description

The presence of an airspace enclosed within a building envelope assembly is known to contribute to the overall thermal performance of the assembly. But, the actual R-value of an airspace can vary significantly depending on various conditions of use, such as the air-tightness of the assembly of materials enclosing an airspace.

Best Practices

This guide details the two main steps to evaluating the airspace R-value: (1) How to determine the type of airspace in the wall assembly and (2) How to determine the R-value for each type of airspace.