People In Glass Buildings
Should Not Hear Their Neighbors.

Glass buildings are definitely beautiful. They let in natural light and provide great views. But it's a given that glass buildings are noisy. And, all attempts to "tone it down" have amounted to a band-aid, not a real solution. Until now.

The Mull-It-Over® Mullion Trim Cap

Adjacent to every glass building's interior is a grid of hollow aluminum tubes that hold the glass in place.These tubes-six inches of space around the entire perimeter of glass buildings-are integral to the exterior curtain wall.The problem is, they create open air gaps that conduct noise and can allow fires to spread, impacting productivity, privacy, and safety. Clearly, a comprehensive solution was needed. And now there is one.

Mull-It-Over Sound Barrier Mullion Trim Caps explained in 2 minutes.

The ExpandaMull

For decades, point-loaded steel-spring partition gap fillers enabled critical differential movement between interior and exterior building systems. But they could be unsafe and difficult to install. Our revolutionary redesign features an extruded aluminum exposed surface, available pre-finished or field painted, with an interior of upcycled, expanding foam. Engineered for efficient installation, this is the industry-changing, high-performing partition gap filler that backs its sustainability statements with a third-party verified declare label. It's changing the way we build.

Featured Resources


People in Glass Buildings Should Not Hear Their Neighbors.

Request Our Environmental Product Declaration (EPD) with Live Cycle Assessment (LCA)

"We'll look forward to talking about the product with more of our clients. It's a wonderfully innovative and ingenious design!"

Leading Acoustical Consultant

"We love the mullion cover and see a continuing need for it on most of our projects."

Leading Acoustical Consultant

"I wish you the best with this product. We all think that this is a terrific invention and was a long time coming. We will be definitely including it on our projects."

Leading Acoustical Consultant

and Canada
and Specifiers

Get In Touch

Learn how Mull-It-Over can help you with your next project.