Are Soundproof Windows Also Energy Efficient?

You’d think so, but you’d be wrong.

There are different kinds of physics going on. Energy-efficient windows primarily depend upon low-E coatings and gas between thermal panes to reduce heat transfer and increase energy efficiency.

Sound-blocking windows, on the other hand, primarily use thicker and laminated glass, and large air gaps between panes to deaden sound. You can easily make a soundproof window energy-efficient by adding low-E coatings. But you can’t easily make an energy-efficient window soundproof without changing its glass and construction.

It’s a balancing act between the performance attributes you deem important for your project.