Wendie Trubow, MD, MBA, IFMCPPresident at Five Journeys, Functional Medicine & Wellness Provider, Best Selling Author, Passionate Champion for Health

Airtight + Vapor Open The Healthy Home Formula @EkoBuiltPassiveHomes

24 Jul 2026 · 1 min

Watch on YouTube

1:09

In this brief instructional exchange, the speakers clarify the distinction between airtight, vaportight, and vapor‑open building envelopes. They explain that while a high‑performance home—specifically a Passive House—should be constructed to be as airtight as possible, it cannot be completely vaportight because some moisture will inevitably be generated inside the building. Therefore, the envelope must incorporate vapor‑open membranes that allow moisture to escape, preventing condensation and maintaining a healthy indoor environment. The dialogue concludes with a practical recommendation for prospective builders: describe the target envelope as “airtight but vapor‑open.”

So what I'm hearing is there's airtight and there's vaportight. Am I correct right there? Yes, no?
Homes should be airtight and vaportight. The other part to that equation is, is vapor open? We have to be like realistic about the house. So a type of home that, you know, is really the optimal type of house to build is a home that's referred to as a passive house. A passive house meaning it's a construction model that results in the tightest home possible. Even a Passive Home has a certain amount of air leakage, and there's always gonna be some residual vapor leakage as well. We have to understand that there will always be moisture to some degree in the building, in the home, and that moisture does have to be able to escape the house as well. It needs to be able to dissipate through proper vapor-open membranes.
So basically, if someone's looking to build a new property, the language that they need to use is, is it airtight but vapor open?
Airtight and vapor open. Exactly.