For the window and door headers, we used 3½-in.-thick Weyerhaeuser Parallam PSL beams. Using Parallam PSL speeds up the framing process as they don’t require any assembly, the way sandwiching a piece of ½-in. plywood between two pieces of dimensional lumber would. Just cut them and nail and screw them into place.

Cut and install. The 3-1/2-in.-thick beams are the same thickness as the 2×4 wall; no need to build up headers.

Although the exterior 2×4 wall provides the support for the roof system, the load is shared somewhat with the interior 2×4 wall in the assembly. Because of that we opted to use Parallams on the interior wall openings as well as the exterior wall openings. In addition, the interior wall carries the floor system, so a little extra header strength doesn’t hurt.

There is more than 4 in. of space between the interior and exterior headers, which allows for an ample thermal break. I’ll detail how we insulate between the headers in an upcoming post.

Parallam headers are used for both the interior and exterior walls.


The ultimate guide to NET ZERO home construction will walk you through the complete process of building a NET ZERO home. In this guide you'll learn: 

  • The process
  • About heating systems
  • Solar, Geothermal or wind?
  • Choosing the right lighting
  • Financial considerations