Insulating Open Web Floor Trusses

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.

Insulating open web floor trusses.

All four edges of an open web truss floor assembly require the installation of a sheathing material to enclose the entire floor cavity and then all joints and penetrations need to be air sealed. 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. Trim pieces of fiberglass insulation using a utility knife so the pieces fit into joist bays along the rim joist. It also allowed us to create a basement ceiling with minimal bulkheads except where load bearing beams are installed.

I have these in my home and i use the space for extra storage as you can see in the picture. All joints in the sheathing material must be air sealed. Any air leakage in an open web floor cavity allows air movement across the entire floor assembly. These trusses typically used as joists have diagonal bracing or struts and are made in quebec by open joist triforce.

The open space is ideal for running wires pipes and utilities. 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. Insul web helps support them. That might be an option but will need to get with the inspector to see if he ll allow it.

Most insulation depots should have them.