Diagram of ideal airspace without air leakage, enclosed airspace and vented airspace

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.

Visit Thermal Insulation for more information on this topic.