Entanglement of Vapor Retarders and Air Barriers in Roof Design

The importance of air barriers cannot be overstated for energy efficiency and moisture control.


Vapor retarders and air barriers – what is the difference? Are we controlling vapor diffusion or air movement? Or both? Air barriers are required for new buildings per the IECC 2015 and IECC 2018, and the importance of air barriers cannot be overstated for energy efficiency and moisture control. We will discuss common vapor retarders and air barriers, how they’re installed, and critical installation details as they relates to the roof and roof/wall interface. A case study with over one million square feet of roofing will be presented to show real-world design and installation considerations and challenges. You’ll also learn that current installation of vapor retarders and air barriers over concrete, steel, and wood decks require different materials and application methods. What’s new, what’s the same, and what to think about when you design roof assemblies in different climate zones and over different types of occupancies with varying construction types.

This course is presented in collaboration with GAF.

Learning objectives

  • Define the differences between air barriers and vapor retarders.  
  • Understand how these materials impact roof design and performance.  
  • Review code requirements and how to achieve compliance.  
  • Outline design and specification requirements to set achievable performance. 
User rating:
Average: 4.4 (165 votes)
 $40  non-member
 $25  member
1.00 LU
  • HSW
  • RIBA


  • Jennifer Keegan, Assoc. AIA

    Jennifer Keegan

    Assoc. AIA

    Director of Building & Roofing Science / GAF

    Jennifer is the Director of Building & Roofing Science for GAF. This position is focused on the...

Course details

Contents: Video, quiz, evaluation

Expiration: One year after purchase

Duration: 0:45

Passing Score: 80% on quiz