Insulating Open Web Floor Trusses

All joints in the sheathing material must be air sealed.

Insulating open web floor trusses.

Open web floor trusses are constructed with 2 x 4 s on top and bottom with a sort of web in between secured with metal plates. To achieve the 16 inch depth we wanted for insulation and an air space under the sheathing we used open web parallel chord trusses as the rafters. That might be an option but will need to get with the inspector to see if he ll allow it. These trusses typically used as joists have diagonal bracing or struts and are made in quebec by open joist triforce.

The floor joists are all fastened to the rim joist which runs along the perimeter. Most insulation depots should have them. Open web joist chase opening. These trusses are 20 deep and we re putting r30 insulation in and that only fills about half the depth.

The joists allowed us to reduce the boxes and bulkhead to hide ducting to almost zero with the exception of inside a main floor closet and the main floor powder room. Insul web helps support them. Trim pieces of fiberglass insulation using a utility knife so the pieces fit into joist bays along the rim joist. Any air leakage in an open web floor cavity allows air movement across the entire floor assembly.

It also allowed us to create a basement ceiling with minimal bulkheads except where load bearing beams are installed.