The Fifth Control Layer – GreenBuildingAdvisor

By RANDY WILLIAMS | June 11, 2025

I was recently part of a webinar where we discussed the basics of the four control layers: water, air, vapor, and thermal. These basic principles of building science were introduced to mainstream construction industry by Joseph Lstiburek a couple decades ago. One of the most influential articles on the topic can be found at Building Science Corporation’s website: BSI-001: The Perfect Wall.

In the webinar I was part of, the participants got into a discussion on whether the industry needs to add a control layer to the list. The organizer brought up the idea of adding acoustics as one of the control layers. Acoustics are important, addressing mostly occupant comfort. A second idea was also discussed: fire. This control layer would move away from occupant comfort and address property and personal risk. Let’s look at both these ideas, then you can make your opinion known in the comments.

The Acoustic Control Layer

Acoustics in building science is the study of sound within or around a structure. It could refer to an exterior noise affecting the building and its occupants, such as a busy highway or a home close to a noisy factory. It could also be an interior noise, sound that transmits between interior spaces, like the teenager who decides to take up a percussion instrument and practices in their bedroom.

The importance of this “control layer” is subjective. A retired couple living in a rural location may not be worried about acoustics, whereas a young family living close to a busy airport might have a different opinion.

Some of the best ways to achieve acoustic comfort in construction are simply designing and constructing well-built houses. Because sound is a vibration or pulse in air…