Is Breathable Underlayment Better?

For decades, felt paper has been the go-to solution for residential roofing underlayment. Throughout the last several years, most roofing companies have transitioned away from felt paper in favor of synthetic roofing underlayment, which is lighter, more durable, and easier to install.

However, yet another underlayment option has begun gaining traction among roofers as of late: breathable underlayment.

What exactly is “breathable underlayment,” and more importantly, is it better than synthetic options? Here’s everything you need to know about breathable underlayment.

What Is Breathable Underlayment?

A breathable underlayment is a specific type of underlayment material that offers a moderate to a high amount of permeability. In other words, it allows water to pass through the material, which can help prevent rot and increase roof longevity. 

Breathability is an underlayment attribute assessed using the ASTM E96 standard. Under this standard, the underlayment’s permeability is rated on a scale ranging from less than 0.1 to 10 or higher. The scale is as follows:

  • Class 1: Less than 0.1 permeability 
  • Class 2: 0.1 to 1 permeability
  • Class 3: 1 to 10 permeability 

A material with a permeability rating above 10 isn’t classified as a vapor barrier under ASTM standards.

Generally speaking, a breathable underlayment will fall within the upper end of the Class 3 permeability range. For instance, an underlayment with a permeability rating of 9.0 would be considered breathable but would still meet ASTM’s criteria for a vapor barrier.

Synthetic underlayment remains a great option for both roofing and flooring applications. However, breathable underlayment might be the better choice in certain cases, such as when installing roofs in warm, humid environments.

Contact Holland Manufacturing to learn more about the benefits of both breathable and synthetic underlayment. We provide both types of underlayment and can assist with all of your vapor barrier needs.

Connect with our team by reaching out to us online or calling us at (800) 345-0492.