I don't know technical details. But I would be skeptical of a builder "upgrading" you to TJI.

We have TJI joists. There are a few spots where we were told steel might be necessary (cantilevers, head clearance), and every time steel came up, everyone (GC, architect, truss companies, city inspector) acted like if we were going to have to go with steel, our budget would be completely out the window. But in the end, with engineers doing some calculations, we were able to "get away" with TJI.

It is fixed contract.
Mine was already priced in for steel beam.

Thanks for you input.

Your question is unclear. What do you mean by trusses in the floor structure? TJI is a trademark for I-joists made by Weyerhaeuser. It is best to call them by their generic name in order to avoid misunderstandings.

I don't know what you are referring to by "steel beams". Are they composite steel and wood joists or floor trusses? Are the joists dimensioned lumber with a beam in the middle that long span I-Joists would replace?

Whatever the advantages, you can make a serious mistake using a manufacturer's span tables to design I-Joists. The most important issue is limiting deflection so that the floor will not feel bouncy. That sometimes requires a deeper I-Joist but the tables and the building code won't help you make the floor feel comfortable.

Who is designing the structure of the house? What does that person think about the change?

Renovator8,

I do not know what is what, just told by my builder that he personally would do TJI (yes, it is from weyerhaeuser) floor joist with wood beams instead steel.

He said normally, TJI is pricer than but they have the promotion which came out even with steel. Also, he mentioned it is better for hardwood floors as well.

He is yanking you chain and trying to make a profit off of it. Have your designer or record make sure it is an equivalent design